Here is my latest project, a linear tonearm. I thought I'd take a step away from the amplifier arena and give it a go, this is 1.5 weeks of work from start to finish and the sound
Is fabulous. Being mechanical without servo, carriage weight is of utmost importance!.


Colin

Push-pull EF or 2EF output stage is probably the most frequently used output topology in class AB amplifiers. It is well covered in renowned design handbooks, like

Self, D.: Audio Amplifier Design Handbook (Newness)
or
Cordell, B.: Designing Audio Power Amplifiers (McGraw Hill)

Authors come to the conclusion that for the lowest distortion in class AB, voltage drop across an Re resistor (usually 0.1 to 0.47 ohm) should be about 22mV, as by Self below (he shows voltage between emitters, i.e. 2 x Re resistor):



Simulators (MicroCap, LTSpice) show +/- similar values. But how about real amplifiers? Is it a general rule? My experience says that sometimes yes, sometimes no, depending on the amplifier circuit.

I am posting an example of the amplifier where this general rule does not work. It is the remake of 1969 Sinclair Z-30 amplifier:



Re resistor (R14, R15) is 0R22. Optimal bias should be (according to Self) 23.1mV per Re. I have measured spectra at moderate power (4R7 load) for 8mV, 14mV and 21mV per Re, i.e. idle current 36mA, 64mA and 95mA. Below are the results.



The distortion is almost same in all 3 cases, slight differences are in high order distortion components. Something does not fit. Let's measure distortion as a function of output voltage and idle current:



And now we have it. It is something that we would intuitively expect. At low power, the higher the idle current, the lower distortion, because the output stage stays longer in the class A. The lowest distortion is for 50mV across Re, resulting in 227mA idle current. Now we are up to 0.48W in class A for 4R7 load (green trace). About 2.5x Self's optimal bias point. So? Isn't it better to design for lowest measured distortion, rather than follow textbook suggestions? And, BTW, this amplifier has flat THD vs. frequency up to 10kHz, measured with 90kHz BW.



------------------------

Edit June 15, 2025:
There were some remarks that the amplifer under test here above was a poor one. I agree, and for this reason I am posting results measured on another amplifier.

So, another amplifier, much better than the oone here above. 3EF topology, 0R22 Re resistors, one pair, 2 x 25V supply voltage, 4R7 load - conditions are same as before. Bias voltage across Re 9mV, 23mV ("optimum") and 40mV.

Spectra:


THD vs. output voltage into 4R7 at 1kHz and BW45kHz:



We have much lower distortion now, however the same result. The "overbiased" setting has lowest distortion at low power, at higher power all settings become equal.

I suspect this topic is covered dozens of times, but I couldn't find the answer I'm looking for.

So I have a speaker design that, in any case, woofers will be crossed to a horn around 800 Hz. This is constant. I'm either gonna use a single Faital 12RS430 in a 70L ported box and have decent F3 and 800 Hz covered, or I will use a woofer like Fostex FW 305 in a sealed box and use a second woofer starting from 100 Hz to the low end.

My question is about the quality of this 100-800 Hz. Which one might sound better? More resolution. The goal is not higher SPL, just more mid/low-mid clarity. Using a low Mms midwoofer vs. a heavier woofer (although Faital's Bl/√RE is higher...). If you have any woofer suggestions that can beat the FW305 in an even smaller box, please don't hesitate.


Thanks for the answers in advance!

Hi All first post.
I recently picked up AudioLab 8000Q and a pair of 8000M monoblocks.
One has a Very slightly audible hum.
Anyway given the age, I'd like to get a basic service done on them.
Would anyone have a PDF of the above.
Kind regards Shane

As title sez - one name, two preamps. Major thingie is AVC Volume attenuation and, sheer luck involved, some free (magnetic) voltage gain.

Reason for 2025 presentation - to show present state (hopefully no further changes ), while there are two preceding threads where you can refresh memory.

Threads:



There is also Papa's tongue-in-cheak thread, I'll say no more, nudgenudge, say no more


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Iron Pumpkin SE, logically, being for single ended signal arrangement, so 5 RCA inputs, and one RCA output; I'm usually mounting doubled RCA outputs, wired simply in parallel.

Iron Pumpkin (no suffix), balanced signal configuration, any number of 5 inputs can be arranged as (permanently) SE/RCA, balanced output can be wired to one or two (parallel) XLRs, or one XLR and (parallel) RCA

2025 iteration, besides major physical change to Big Motherboard, is also having altered arrangement of Iron Turtle (AVC) module,e with (new) 28 steps arrangement.
Step 24 is 0db,
step 23 down to step 1 are each -2db,
step 25 to step 28 are each +2db.
So, ranging from -46db to +8db. Previous arrangement, with 24 steps and jumpers for (permanent) gain set stays as solution for kit/finished preamp with physical/rotary switches controls.

And, yes, now there is a choice between Metglas and Finemet cores; what's the difference between two - pretty much the same as between Cinemag normal nickel and CInemag high nickel - normal isn't much worse than high nor high is much better than normal........ but when you shoot, you usually shoot for better sleep

Dazzling, Shiny and Overwhelming characteristics speech: Fully dual mono (custom made 20VA Donut for audio circuitry is having separate secondaries for channels; custom made 10VA Donut feeding all things Logic and switching), ultragigamega shunt regs, OhYeah! Toshiba For Audio JFets serving in buffers, precious Fujitsu relays for everything what's switched, volume attenuation as explained above, yadayada.......

Button on front, fiddle left-right to set volume, push for incremental cycle through inputs 1 to 5.

Fancyschmanzy remote having same functions, plus mute/unmute buttons.

3.5'' TFT as Eye Candy, Tesla writing for ZML Greetings, then Led Zepp font for functional screen.

I am working on this Bogen Challenger RC412 (tube receiver from about 1960) that has a few problems, one of which is a blown line choke at the AC in. According to the schematic it is 1.9uH, I have not been able to find a replacement.

Any ideas?

See attached pics.

Hello everyone.

Following the realization of several people of a class A amplifier (USSA-5 of Fab), I decided to draw a PCB dedicated especially to this one but that can be suitable for any other amplifier.
I wanted to do something fairly universal and practical and I told myself that this PCB might interest more people.

Features:

Size: 160mm x 100mm.
Possibility to put four capacitors up to diameter 40mm.
Possibility to put diodes (to220) soft or high recovery (capacitors provided).
Capacitors in parallel on the inputs of the diode bridges.
Possibility of putting an 'RC snubber' on the inputs of the diode bridges.
Possible resistances between capacitors from 5W to 10W.
'Bleeder' resistors from 3W to 5W

The latest version brings the possibility to put 5-legged capacitors and TO247 box diodes.


Update: Schematic:




Silkscreen:

EDIT: The problems encountered initially have been solved in this thread by numerous tests and with the assistance of jpk73 and mdardeniz as well as the contribution of element of the work of JeffYoung. I give files here and i will see to establish component list.

Hello everyone, three years ago I built two NAP 250 clones from naim, these were my first DIY projects and even if they already give (very) good results, I still made some errors so I wanted to launch myself into a new, more successful version, so I reworked all this on the net and on this forum as well.

I redid all the diagrams in Kicad directly in order to improve the design of the PCBs and their skillscreen printing by sticking as closely as possible to the original NAIM
I placed output transistors on the PCBs and not wired in the air which improves stability and construction
I changed my PCBs to double-sided 70 microns instead of double-sided 35 microns like on the old versions
I note as my work progresses all the verified information in my diagram
I went through plenty of pictures of the original Naims to determine the correct values and was able to correctly determine and identify three versions of the phase correctors to the driver transistors as well.
I determined the values of the phase compensation resistors according to the output transistors used.
I was able to correct an error on a value of a capacitor, on the input filter it is a 470pF and not a 330pF.
I changed the output capacitors on the regulation card for "high" ESR capacities >1.7ohms which corrects an oscillation problem.
I was able to determine that without the protection circuit on the amplification board the sound is not particularly improved and that the offset is much longer to go down when switched off


this time I use the original drivers (MJE243/253) on the regulation cards and not those recommended by Neil mcbride which greatly improves performance and stability
I then searched for better substitutes for the unavailable transistors by closely studying many datasheets namely the VBE (ZTX384 or ZTX108) and the output ones, the Mj15003 not being the best.

I thus tested with the oscilloscope and by ear for the VBE the 2N2222A in comparison with the 2n5551, my choice fell on the 2N2222A which seems to me a little better to the ear but also on the noise in the data sheet. I also tested the ZTX690B and 2N6428 it's works but it's not better.

For the output ones I tested:
BUV22 but they are not really suitable for the ear it is not very convincing and I think that the bias and the drivers are not suitable, there is too much crossover distorsion with MJ243/253 drivers.
Mj15024 they seem better to the ear than the Mj15003 but they are only 15A so there is no point in taking T0-3 boxes, there are also too much crossover distorsion with Mj243/253
2N6341 They are suitable and sound better to the ear making 40mhz for 25 amps they are probably the best performing so I have chosen it for my new amplifier.

I had noticed Phase compensation problem with 2N6341, I didn't initially understand the problem, I was able to fix it as you can see later in the topic.

The adjustment of the phase compensation is more or less delicate it depends on each type of power transistor used but it also depends on the PCB layout. If the MJ15003 and the BUV22 are quite easy to adjust, the same is not true of the Mj15024 and especially the 2N6341. Having done the setting for the PCB layout used in my amplifier (V2.1) I cannot give the optimal values for the latest files I give here (V2.5)

I give the correct values for version 2.1 so that you can directly use these PCBs if you want to build the same amplifier without having to do the adjustment. For those who would like to use the latest more advanced version, you will have to make the adjustment yourself. The rest of the topic will show you how to do it.

For the components I chose the original MPSA06/56 from diotec and not those from central component as for my old creations, indeed central component makes copies and not originals, something that I did not know.
For capacitors I chose for the amplification card very high voltage WIMA and also for the miller. (on my old version I took 39pf in Mica, there I took 33pF and 47pF)
i take organic polymer low esr for the AMP BOARD
For the NAPS Board please note output capacitors 10Uf must have a esr >1,7 ohms for stability of the supply.
For filtering I chose a very high quality EPCOS 22000uF 100V capacitor 4 milliohms of ESR, 57 amps of rejection capacity in place of the previous Mundorf 22000uF 80V (7 milliohms 33Amps)
All my components are ordered on Mouser by preferentially choosing the manufacturers

For the resistors I chose to switch to 1W or 2W in metal layer in order to further reduce the noise against 0.5W on my previous realizations
only the 0.22 ohms on the output is wound due to lack of availability.
For the plugs I chose larger plugs more suitable for 2.5mm wiring and above all offering better contact and better manufacturing quality.

For the pairing of the transistors I invested in a second-hand RIGOL DG1022Z BF generator which allowed me with my oscilloscope in XY mode to draw the characteristic networks of the transistors which I had not done during my previous achievements, I had simply used the HFE.
I ordered series of transistors and as I had other of my previous orders I was able to operate pairings on:
BC550C in LTP are matched
VAS ZTX653/753 are matched
MPSA06/56 on the protection circuit are matched
MJE243/253 in drivers are matched
2n6341 output are matched

On the regulation boards I used identical paired MPSA06 series and also paired MPSA56 series
MJE243/253 drivers and 2n6341 output drivers are also paired
capacitors are MKP higth voltage general purpose
resistors are 1W-2W metal too

For the variable resistors I take multi-turns unlike my previous amplifiers, in fact the single-turns are not precise enough and can move with time and vibrations.

The transformer is a high quality encapsulated nuvotem talema 500VA to reduce vibration and ground buzz

The 4 cards are mounted, I still have the last heatsink to manufacture, I am waiting for my aluminum case and the last parts in order to start the final assembly, I expect to receive the case in less than 15 days.

to note unfortunately on my PCBs I made a footprint error on the 39pF capacitors which were far too big, I was deceived by a bug in the Mouser search system which was giving me 4uF capacitors instead of 40pF.. .
I have since corrected the error in a new version of my PCBs in Kicad but my PCBs being already ordered I use those with this footprint error.


Here a caracteristics of a transistors i use two différent resistor for the base 100K and a 3300ohms for testing different currents


Here you can see phase compensation problem

First regulator board, note larges Capacitors are organic polymers low esr and not electrolytics. C105/205 later changed by united chemicon electrolytic with 1,8 ohms ESR
On the first amp board there are not the circuit protection i want to test with ears with and without the circuit protection when the amplifier will be finish.
here on a 2Ohms resistor
here the test of stability on the regulator down it's a power rail of the regulator board it's about 100-150 mv variation on a square wave 1000Hz 100mV in the amp
47pF are on the other side...

a heatsink with his isolate board to isolate from the PCB

Here V2.1 correct values for phase compensation are:
R26 1800 ohms
R27 1800 ohms
R29 2000 ohms
R30 2200 ohms
(note for the drilling of the heatsinks that the two output transistors are not perfectly aligned either on the AMP BOARD or the NAPS BOARD)


Here the last files of schematics and Kicad PCB V2.5 (V2.4 For regulation NAPS board), This version is better the holes are aligned for the T0-3 but the values for the phase compensation must be developed:

Which are the interesting tubes available in mesh plate versions? I'd nominate the 27 and AZ1 or AZ11 as ones I've used and liked for instance.

Any explanation why mesh plates sound good?

Hi, need to know correct name of these footprints....
on Easyeda there are tons and in Eagle tons*tons*tons....

In cases like this, how should I behave?

Thanks!

Hi, I’m looking to confirm the TS specs of this 6.5” driver as my measurements using REW/Datsv2 don’t quite sync with the specs on the PE website.

Re, 3.37, 3.71
Le, 0.48mH, 0.8mH
Qms, 2.99, 3.4
Qes, 1.4, 0.875
Qts, 0.95, 0.7
Vas, 0.65ft3, 0.756ft3

(spec first, my measurements second)

Has anyone measured their YD166-12A drivers and can share your T/S measurements?

As the title states, this is a thread dedicated to dome midrange drivers, specifically any larger dome driver at least 50mm or 2" in diameter intended to be used in a 3 way or larger speaker design.

Being there isn't a good collection of data on this rather rare type of driver and its use, it would be nice to have it all in one thread. My goal was to give anyone interested in the successful design of a speaker using a dome midrange a solid starting place to gather or share the info necessary to design a new speaker or to modify an existing design to use them ie. xover, baffle modifications, etc.

If you have any specific or technical info (measurements, graphs, data, xover design, pictures, links etc) regarding your favorite dome midrange or a specific technical question, please feel free to share it in this thread.

Please keep your post to the point and avoid any strong subjective opinions. I was hoping this thread could accumulate as much relevant info as possible. Thanks in advance for any productive shared info.

Single End Class A, we can see often.
What do we really mean by saying some amplifier is SE?
What is the opposite?
Is there amplifiers with SE in class AB? Or not?

This should not be confused with single supply vs dual supply.

Hello Community,
I’m in need of some help. I’ve gone through a few hundred pages of the main IanCanada thread, used ChatGPT and I’ve run out of things to try.

I’m building a transport to connect to my Laiv uDAC. The base parts are a RPI 3b+, TransportPi Digi/II, PurePI II and IsolatorPi III. I’m using Ropieee as the OS and sending music from Roon as an endpoint. I’m using the HiFi Berry Digi+ Pro driver in Ropieee. I’ve been experimenting with both I2S and Coax outputs.

When I connect everything without the IsolatorPi III it works amazing. The problem is when I insert the Isolator into the mix, I get no audio output. My DAC clearly sees the PCM signal over I2S and Coax, but no sound. I tried the I2S generic driver and got static so I feel like this is a software/driver issue, or some random jumper setting, or something is just on mute and can’t be unmuted, or I have a bad board?

Pics are below to see how things are all connected, jumped, powered, and lighting up. I’ve read around and I started a new thread because it seems I’m not the only person with this problem, so I figured I’d create a searchable way to fix it.

Thanks for the help!

Just make things more clear on bass segments and panels.

Green are the delay rings only above 1 kHz.
White is mid-bass.
All the rest is bass.

This is a 4 panel model, for 6 panel models add an extra bass panel on the top and the bottom.

By popular demand, here is a new thread devoted to PETTaLS flat panel speaker simulation software, developed by Dr. David Anderson. Flat panel speakers may also be referred to as bending wave speakers, or DML speakers.
Let's use this thread to discuss topics specific to the use of and improvement of this great new tool. Topics could include, but are not limited to:

• new release announcements
• questions about how to use it
• features you'd like to see
• possible bugs
• interpretation of results
• other....

The free version of the software is available here:

PETTaLSFree

Some videos about the software are here:

PETTaLS Videos

Eric

大家好！ 我是新来的。 我喜欢摆弄功率放大器、前置放大器，并IC功率放大器。 渴望向你学习和分享我的经验。 期待着聊天！

Hi all

There is some great contributions with open source designs and gerbers on diyAudio. The hardest part is deciding which one to build 🙂.

I think some of these have made their way to Aliexpress sellers. Sometime ago I came across the Ultimate Fidelity 100w amp on AE which appeared to be one of the revisions from the thread here.

Does anyone know of any boards/kits/amps from AE based of designs from here?

This is a design I've had in use for rather a long time. It started life as a design exercise to see if I could do a more space-efficient board for my original AEM6000 based amps, as I wanted something that would fit on a 50mm high heatsink. Along the way it changed a little from Tilbrook's original in topology, and rather a lot in component choice. It has better performance than my original design, both through a better tighter layout and also through the use of faster transistors.

I've built a bunch of these, using both Renesas and Exicon lateral MOSFETs, and subjected them to all manner of abuse. I had one fail, due to a leaky mica compensation capacitor (see noiseUnit speaker thread), but apart from that they've been rock-solid.

Lots of component substitution is reasonable. I like to use MELF resistors, but that's mostly just bloody-mindedness. An exception is the feedback divider. No, it won't work with vertical MOSFETs.

I have checked just now, and every single component is currently (December 2020) available.

The design is free for use for non-commercial purposes.

In the design folder I have placed:


Google drive containing design files.

Hi I have a pair iof these old 15" Nakamichi car subwoofer drivers.
I would like thoughts on if they are useful as Subs in a HT & music system?
What enclosure type you would go for?

My priorities are
- clean tight bass rather than necessarily getting 20hz
- smallest reasonable foot print and high sensitivity as they will be pairing with high sensitivity mains.

I have an electronic crossover with variable gain so can match them and am considering shelling out for a miniDSP.
Cabinet making is a hobby so a horn is not out of the question so long as its not a wardrobe sized monster.

• Resistance: 3.2 Ohms
• Frequency Response: 32 Hz
• BL: 17.71
• Mechanical Q (Qms): 4.57
• Electrical Q (Qes): 0.5431
• Total Speaker Q (Qts): 0.531
• SPL: 90dB @ 1W/M
• VAS: 90.579 Ltrs
• X-Max: 18.5mm one way (37mm Total Linear movement)
• Voice Coil: 4 inch Aluminium (black anodised) former 4 Layer winding with thermal coating
• Cone: Bi Laminate combination Paper Pulp with woven Fibre
• https://www.elite-electronics.com.a...xW_Vs7CAirwwgUQiUM4VrXX4cpeWfSpkhfiqCWh-Lhwm2

Anyone know of a good source of Felsic caps as used in Naim kit (HiCap etc). I contacted the manufacturer and they put me on to their distributor in the UK, but they have a minimum order value of £500...

Hello everyone

I have recently been in contact with Mr. Rullit regarding his exceptional field-coil drivers, and I intend to place an order for the nine-inch “Super Aero” model in the near future. At present, I am in the process of researching which type of speaker enclosure would best complement these drivers. However, I must note that my options are somewhat limited due to certain non-negotiable constraints—most notably, I am unable to accommodate large horn systems.

To provide some context: I reside in a historic manor apartment, where my dedicated listening room measures approximately 25 square meters (5 × 5 meters), with ceilings reaching a height of 2.7 meters. My musical preferences primarily include classical and jazz repertoire, ranging from solo performances to chamber ensembles and full orchestral works. As an amateur pianist, I place a high value on natural sound reproduction—one that conveys holographic depth, dimensionality, and body, while offering a rich and organically pure tonal character. From my impressions, Rullit’s drivers seem to embody these qualities remarkably well, particularly in terms of transient speed and natural timbre. The sound is airy but has body, it is transparent but has character, it is neutral but has depth. In order words it has the emotional realism that I strive for.

As mentioned in my introductory post, I am quite new to DIY audio projects. However, I have allied with skilled people —one of whom has experience with CNC machining, and another who excels in veneering speaker cabinets with real wood finishes.

From my conversations with knowledgeable individuals, it appears that Rullit drivers are well-suited to a variety of enclosure types, including dipole, front-loaded horn, open baffle, and resonant designs. Personally, I am inclined toward dipole or resonant enclosures, primarily due to their more manageable size. Unfortunately, I believe my room is too small to accommodate horn systems effectively, and open baffle designs would require substantial space behind the speakers, which is impractical given my current interior layout. I have attached photos of possible solutions.

I would be most grateful for guidance and recommendations that could assist me as I move forward with this project. Even specific design plans would be perfect! Any reflections, suggestions, or insights would be sincerely appreciated.

Thank you very much for your time and considerations

Onsemi announced that KSA1381ESTU is end of life with a last order date of Jan 5, 2025. Is there any interest in a group buy for these?

My thought is to combine it with a group buy of 2SC3503E which is available from Rochester Electronics (link here), but only in large quantities (1000+). This makes for a good pairing as KSC3503 is currently only available in D grade.

Lot sizes will be 100 pieces of each device.

As this would be a large cash outlay for the initial purchase, we'd probably need to have money up front. We'd have to backorder them as both Mouser and Digikey are currently out of stock, but accepting backorders. Maybe it'll arrive in time for Christmas.

I will keep the first post updated with anyone interested in participating.

PRICING UPDATE:

Pricing factors in the price to order, taxes, shipping and repacking materials with a bit of a bump so I don't hopefully loose money on this.

Round 1: $30/100. For example, 100 x 2SC3503E and 100 x KSA1381E would be $60 + shipping.

Round 2: $30/100 for 2SC3503E and $35/100 for KSA1381E. The higher price in round 2 for KSA1381E is due to a price hike on Mouser's end.

SHIPPING:
For shipping, US will be $5. International will be $20 if the quantity is 100/100. If over this, I'll PM an estimate. This is due to the weight threshold where international shipping prices increase.

VAT: If there is VAT in your country, I understand this will be collected from the recipient, not paid by me.

TIMING UPDATE:
The Mouser order for KSA1381ESTU has been placed. Its backordered at Mouser with a restock date of 11/11/2024 (if Mousers date is accurate).
Domestic orders arrive in the second half of November.
International orders will go out via USPS international which shows shipping times of 1 to 4 weeks.

PAYMENT:
I'll send payment info once I get close to being able to ship. I have PayPal and Venmo.

April 2025 UPDATE:
The Mouser order for KSA1381E failed to come through. Mouser canceled the order despite it being placed months ahead of the final order deadline. It's unclear if this is a Mouser or OnSemi issue. We looked extensively for alternate sources of KSA1381E but could not locate anything that was cost effective. It was determined that KEC KTA1381Y was the next best alternative.

April 20, 2025: Profusion order for KEC KTA1381Y placed.
April 25, 2025: Profusion order received
April 30, 2025: Estimated Ship Date for Round 1 order (for those that have paid)
Early May: Payment instructions to be sent for Round 2 participants

ROUND 1: Closed for new participants (Shipping April 30 ,2025)



ROUND 2: Closed for new participants (Shipping early May 2025)



ROUND 3: Open for new participants (based on available stock)

Hello everyone, I have just joined the forum and am looking for the development and production of electronic products related to in-vehicle entertainment system. Recently, I am looking for some platforms that support PCB/PCBA online automatic quotation, hoping to simplify the process. It is best to directly upload Gerber files to automatically calculate the price without the tedious manual filling of details such as number of layers, thickness, materials, etc.
If you have used similar tools or platforms, please recommend them, thank you!

It's been 3 or 4 years since this newbie started learning tubes from the wealth of knowledge here. In that time I've been collecting schematics, studying, experimenting, buying parts and tubes that mostly just sit, fun to me but weird to my wife. A few months ago I fell into starting something ambitious, figuring out how I would go about building a direct bias 300B PSE amp with dual PSU's. Inspired by Andrea Ciuffoli, because I kept coming back to his 300B PSE schematic over time. I began with his schematic and dumped every thought I'd need to remember about making one myself onto paper. Simultaneously I've wanted to make dual "boat anchor" PSU's for it, inspired by the Border Patrol amp I really liked at AXPONA. The intention is for the boat anchors to have variable B+, umbilical connected to the amp, so I can re-use the PSU's maybe for a second project. So I'm imitating Andrea Ciuffoli and Border Patrol here but learning. I've attached the schematic as of today, if anyone wants to comment, recommend, help, find errors, etc. Along with the electronics, I'm also doing the mechanical design in 3D CAD as I hope to machine and fabricate the chassis all myself as well. As that gets farther along I'll post 3D models too. Thanks!

Last schematic update: See most recent "last update" post from me.

The Keystone Sub™ cabinet works well with a variety of speakers of quite different parameters and sizes.
The Keystone is named for it’s exit shape, similar to a keystone. Like keystone lens correction for off axis projection, the keystone exit corrects some frequency response problems that result when a rectangular exit is used with the particular fold pattern employed in it’s construction.

Any person wishing to duplicate my Welter Systems designs for their own use is welcome to, any person or corporate entity that would like to produce them for sale please contact me to arrange a licensing deal to avoid violation of intellectual property rights as defined in section 27 of the Universal Declaration of Human Rights adopted as international law in 1976.

Similar in size to many 2x18” cabinets, exterior dimensions are 45 inches tall, 26.5 wide, 22.5 deep.
Weight is around 150 pounds, 68 Kilos, depending on the drivers and plywood used.
More information about the design are available in these posts:

Tapped Horn Vs. Bass Reflex Case Study - diyAudio

Horn Extender/Wave-guide for TH

Tapped Horn Directivity

Corrected plans are available in post # 487, including parts layout, thanks to NEO Dan, with the exception that the bottom of part "F" is 89 degrees, the front of "G" is a 5 degree angle, the back of "G" is 3 degrees as shown in post #478.
The previous plans #94 and #97 (thanks Oliver) have some errors due to my providing Oliver with some incorrect numbers, sorry for the confusion.
Assembly instructions are in post #1525:
https://www.diyaudio.com/community/...ng-18-15-12-inch-speakers.185588/post-7043072
Photos of finished Keystone Subs and the bass reflex (BR) cabinet as it was used for testing are in post 1039.
Photos of the cabinet interior are in Post #99 and clarification of the 9 braces used in #206 and #451.
Distortion results are in post #12, there is a typo: The * should read: third (odd order) harmonic louder than second.
Those tests were done using 77 volt sine waves (kids, don't try this at home!!), a bit less than "full power", used the 1500W AES power specification of another B&C driver rather than the 1700 W rating of the 18SW115-4.
The upper reduction in output noted in the TH sine wave tests compared to the BR tests are due to the TH upper pass band low impedance points, while the BR has a steadily rising impedance. As the tests were started from low frequency, which has better heat pumping, and ended with upper frequencies, which don't pump as much heat from the voice coil, the upper pass band compression noted in the TH compared to the BR was due to the lower upper impedance causing voice coil heating, raising impedance, causing "power compression" at 77 volts, after less than 50% duty cycle over a few minutes time.

Hornresp inputs are available in post #96 and 130.
The link explaining how distortion was measured expired, an explanation is in post #315, and a correction in #316.
PASC built a Keystone Sub TH ("tapped horn") and a xoc1 18" TH and reported his findings in posts #114 & 115.
The lower frequency response corners using a partially covered exit, ("step down" mode) is in #262, but the description is wrong:"TH18S20" has the upper 5 inches of the exit covered with plywood, exit is 20" from bottom to top. The "step down" cover results in as much as an 8 dB increase in 30 Hz level (with only 8" from bottom to top left open), but with progressive losses in the upper bass range, so for most music the trade off is not worth the extension.

The Keystone B-Low (a low "B" note is 30.87 Hz) testing started early October of 2017, initial reports using a B&C18TBW100-4 driver are in post #1135. Photos and the response curves with the B&C18TBW100-4 and the 15” Dayton PA385S-8 and a "step down" cover plate are in post #1167.

Comparative tests using the Keystone Sub loaded with an 18 inch B&C18SW115 (four ohm nominal), a 15 inch Eminence 4015LF (eight ohm), and two Eminence Lab 12 (6/2 =3 ohm) were conducted in March of 2011.

The same 16.6 inch diameter cut out was used in each case, the 4015LF used a “doughnut” adapter, the Lab 12s used an adapter that centered the two speakers on the cut out and provided a stand off so they would not slap at high excursions. The Lab 12s have a "saddle shape" frequency contour, the 96 Hz peak needs to be removed with EQ for flat response.

There are a few other peaks and dips in the response curves due to very windy conditions, often requiring waiting minutes between gusts to record responses. Test day was literally a sand storm, the bottom of the cabinet was filled with coal dust and tumbleweeds after.

All the speakers were driven with the same level. The 4015LF is actually about the same sensitivity as the 2x12 pair, since it has about double the impedance minima.

A BR (bass reflex) LAB 2x12" (36 FB) cabinet, exactly half the size of the Keystone sub is shown in the blue trace, it’s upper response is slightly reduced due to a Butterworth 125 Hz filter, all the other subs used a BW 1000 Hz filter.

As can be seen the 15.5 gross cubic foot Keystone Sub TH loaded with the B&C18SW115-4 sensitivity averages 6 dB greater than a 8.75 gross cubic foot BR.
Twice the power and drivers in a pair of BR cabinets weighing at least 40 pounds more, and occupying 2 cubic feet more trailer space are required to equal the SPL output of one Keystone Sub. The pair of BR would be capable of few dB more output below 45 Hz, the Keystone Sub +3dB or more SPL above 45Hz, more "punch" where you may want it.

There are subjective sonic differences between the TH Keystone Sub and the BR cabinet when they are driven hard enough to approach the thermal and linear excursion limits of the driver. Running subs at "full tilt boogie" is common for most applications desiring the maximum output for the minimum trailer space, and the most "bang for the buck".
1) The TH cone is under more stress at the same input voltage than the BR, this results in slightly more distortion, and the distortion spectra is at different harmonic points- the TH sounds "louder" when driven hard.
2) The BR looses LF output due to "port compression" (turbulence) relative to upper level. The TH does not suffer from any "port compression", but suffers from more upper pass-band "power compression" than the BR. The net result is the TH sounds a bit more "aggressive" (more 45-100 Hz output) at low drive levels compared to the BR, but at high drive levels, sounds "fatter" due to the LF range not reducing, while the upper range is "compressed".
These two differences are program dependent, music with wide dynamic range won't reveal the thermal problems, while compressed and droning LF content will increase both, subjectively and measurably.

Subjectively, with the same drive level, the Keystone Sub using the B&C18 seems a bit more “punchy”, more stuff falling off shelves in the shop, and more "foot feel" in the sidewalk vibrating during out door tests. The B&C18 takes full power from a bridged Crest CC2800 effortlessly, while the Eminence 4015L 15" seemed a bit “wheezy” at a lower drive level, the Eminence LAB 2x12" in between.

The Eminence speakers used in the tests are a bit more sensitive, the 4015LF would be the best “bang for the buck” output per watt/cost for low power applications. Making a slightly wider cabinet would allow two 15 inch speakers to fit, which would probably allow about 3 or 4 dB more output at the low corner, and 5 or 6 dB more upper level with only about 20% increase in cabinet size. The Lab 12s sound cleaner, and with the same voltage applied are louder than the 4015L. For those with limited amplifier or AC power or budget, the Eminence speakers are good choices for the Keystone cabinet.

Looking at the low excursion of the Keystone vs. BR in the region from 50-90 Hz, it is evident that the cone is under a lot of stress, quite audible sounds of distress may be heard at high drive levels using lightweight (low Mms) cones.

The very stiff cones of the Lab 12 and the B&C18SW125 can take the stresses and sound clean, when pushed hard the 4015LF sounds pretty awful.

The B&C18SW115-4, though less sensitive than the Eminence speakers, will go a lot louder with a cleaner sound given more power due to its greater linear excursion capabilities, more even BL curves (the magnet "pushes" harder further), more power handling with better cooling, and a super stiff cone and suspension.

Using Hornresp simulations at rated Xmax values, (and impedance minima) average level from 35-100 Hz, the Keystone has these output levels:
BC21SW152-4 131.6 dB, 92 volts, 3.4 ohms, 2489 watts
BC18SW115-4 130.1 dB, 76v, 3.43 ohms, 1683 watts
BC18TBW100-4 127.8 dB, 59v, 3.32 ohms, 1048 watts
Eminence 2xLab12 126.3 dB, 36.5v, 2.22 ohms, 600 watts (300W per driver) 128.4 dB at 40 Hz.
Eminence 4015LF 121.9 dB, 38v, 5.17 ohms, 279 watts

The average impedance is higher than the minima, closer to the nominal rating of the speakers.
Other than the 4015LF, which did not sound good (by comparison) in this cabinet, the other drivers are capable of considerably more peak level (140+dB) without sounding bad.

I consider "safe" limiting for the Keystone sub using a B&C18SW115-4 to be as follows:

A) Use the DCR of the loudspeaker to determine the voltage setting, the DCR of the B&C18SW115-4 is 3.3 ohms, the minimum impedance of it loaded in the Keystone Sub approaches that value at Fb, where cone movement (and forced air cooling) is also at minimum.
B) The manufacturer's "Continuous Program" rating of 3400 watts is OK for peak limiting, using short time constants of a few wavelengths duration.
C) Long term "RMS" limiting with a time constant of longer than 500 ms (milliseconds) should be no more than half the rating of 1700 watts (850 watts), as AES ratings are conducted in free air (the actual power dissipated is less than 1/2 the nominal "wattage"), while driver's voice coils heat up far more when loaded in the Keystone "tapped horn" due to the far lower average impedance than the free air test. If you tend to get "heavy handed" on the volume fader playing compressed music over long time periods, use 425 watts.

If using other drivers, substitute their "Continuous Program" and 1/4 to 1/2 of the "Nominal" RMS rating for peak and average limiting settings, using the DC resistance, not the nominal speaker impedance for figuring the compressor/limiter threshold voltage settings.

Compressor/limiters will not protect a loudspeaker from excursion related mechanical damage.
Your Keystone sub should use a 30Hz 24 dB per octave Butterworth high pass filter to protect drivers from mechanical damage if amplification capable of exceeding the driver's Xmech rating are used.

Art
Welter Systems, Inc.

By way of background, I've been intrigued by some of the very simple amplifier circuits presented here, and have wanted to explore quasi-complimentary designs for several months now.

Inspiration for this project has come from Gareth (TGM lineup), Hugh (AKSA-55) and Carlos (original DX amplifier). I had originally planned to assemble Quasi's Nmos200; however, difficulties procuring boards has left me with a bag of IRF840 MOSFETs and nowhere to turn!

The schematic I present is as simple as I can possibly make it, without comprosing it to the point where it is just a giant oscillator. If you can think of any way to reduce the parts count further please let me know. Likewise, if I've omitted something essential for function or stability I'd like to know too.

I know there are 101 ways I can make this 'better': CCS on the LTP, degen resistors, bootstrap or CSS on the VAS, RC filters on the rails, etc. For this project I want to keep it as simple as possible and then my next project will be to embellish this circuit with some extra features.

Please let me know if there's anything I've missed (noting my Keep it Simple design ethos) and check my R values.

Next step will be to prepare a board layout and send the Gerber files to my board house.

Edited 30 September 2016:

Please refer to the post #1384http://www.diyaudio.com/forums/soli...mentary-mosfet-amplifier-139.html#post4844098 for the latest circuit:
http://www.diyaudio.com/forums/soli...mentary-mosfet-amplifier-139.html#post4844098

Here is a DIY Ribbon like speaker from a french guy
François DEMINIERE
His site:
http://home.tele2.fr/mon-site-perso/

Very impressive design with large band of operation.
(250-20000 Hz), SPL 102 dB
Still need a Bass reproducing device to support this
mid high ribbon.
Too bad their is no photos of some prototype!!!

Mandrake5

Hello,
I am looking for plans for a cabinet to fit my Scan-Speak P17WJ speakers. I have recently built DDVP-20 cabinets for my Visiton BG20s. I loved the bass and would like to get a similar sound again. Can you suggest a model I could make? Thanks Very much.
Rick

hello all,

i need new speakers, so i want to ask your opinions about this 2 DIY Kits.
The baffle at the ekta grande looks like a promise for a good soundstage.
The 7741 use the newer illuminator chassis.

Ekta Grande

Ekta-7741

i want to go for passive xover this time, even i own a pair of hypex 123 amps which would reduce the cost.
they are a good tool when its comming about making the xover fast and easy and active speakers are always great,but aside of this really big benefits im not so happy.

My room> 5,22m in lengh and 3,85 in width
the speakers are placed left and right of a lowerboard where a 65" TV is. (yes,not perfect, i know it has an impact on the reflections)

on the ceiling i have 18 pcs 50x 100cm Basotec panels which are 5cm thick.
on the opposite site of the speakers is the couch and above that a 240cmx140m acoustic picture which is filled with 5cm basotec panels.
so the treble is well damped, maybe a little to much 😉

Music, well all kind music except jazz.(classic is really rare, maybe one or 2 times in a year.

what i like on speakers, details and more details, a good seperation between instruments.silent things to hear that get lost on cheap shoutboxes.

my past system was a 4 way active seas excel system. with an 35cm baffle.

So, what do you think are the pro and cons of those 2 Kits ?

Hello everyone,
I decided to build my first RIAA phono stage, using OPA1656 and the schematic shown in the datasheet.
Where possible, I tried to use 0805 smd components for resistors and capacitors (exclusively Thin Film and C0G/NPO), except for the two 100nF that decouple the power lines. These are X7R. About the four 100uF capacitors, I chose Nichicon UES Bipolar.

The only change to the circuit concerns the removal of the 150 pF capacitor (for the capacitive load), replaced by three capacitors (22pF, 47pF, and 100pF) selectable or not, through a 3x SPST Dip Switch, for 8 possible combinations of capacity (0, 22, 47, 69, 100, 122, 147, 169 pF).
Considering that an average interconnect cable has a capacity of around 100pF, being able to add values between 0 and 169 pF, allows you to optimize the right input capacity in the most critical range of many cartridges (100 - 250 pF), especially those that prefer low input capacities.

I attach the schematic and some images of the PCB layout, in its current state. I have already made all the connections, but I have not yet added the ground plane on the bottom, so as not to confuse the traced tracks. I used 20 mills traces for all the signal lines, and 30 and 35 mills, only for the power lines.

But before completing the PCB I would like to hear some opinions on the layout and ask some questions:

1 - Is this preliminary rooting good enough, or are there obvious errors? Can it be improved with small changes?

2 - For simplicity I used classic 2.54 mm connectors for inputs and outputs. The input RCA connectors will be the standard through-hole type, fixed to the rear panel.
If placed at a distance of about 35 mm from each other, they will be located almost exactly above the two fixing holes of the PCB, on the input side, with the advantage of being able to use really short input cables (15 - 20 mm or even less). Slightly longer cables for the outputs I think are less of an issue.
From a sonic point of view, would it be better to use different connectors?

3 - About the Output capacitor, the last two lines of page 21 of the datasheet, state:
"... C5 is chosen to be the same value as C4; for simplicity however, the value of C5 must be large enough to avoid attenuating low-frequency information."
In my schematic, C5 corresponds to C13, C14 (100uF).
How do I check or calculate if the value is large enough, to avoid attenuation at low frequencies?

4 - Any other suggestions or criticisms, will be useful. 🙂

Regards,
Marco


I attach the schematic and images of the pcb in its current state.

Schematic From OPA1656 datasheet:


Actual layout without ground plane:


Board preview:

I have always wondered what components and topologies the 1RU class D amps out of china use.

So I recently purchased a 1RU "clone" amp, 4 channel, both as a backup and as a loaner amp while repairing other amplifiers.

I promptly opened the box, and before even powering up, disassembled it.

This particular model is the new GaN Fet version. Claimed power is 3500w/8 ohms x4. I measured just over 3000w into 8 ohms sinewave, continuous, single channel driven. I suspect this power will fall as more channels are loaded.

The output channels each have 2 pairs of AOK033V120X2 GaNFETs (Alpha and Omega semiconductor), with series MBR60100PT Schottky diodes by "MHCHXM", and antiparallel BYC30W-600PT2 Hyperfast diodes by "We En"

The driver circuit was underneath the heatsink and I am yet to disassemble it to that level, however I did see many 74HC06 hex inverters, and and some other 74HC series chips.

Bad design elements are multiple through hole / surface mount electro's under and around the heatsink, which would experience higher heat levels.

I will post pictures soon.

-KAB

Hi everyone!

So I'd love some feedback on this design I'm working on before going into pcb design.

I have the TC Monitor Pilot, but it only allows for output selection and volume. It's nice and the design with the remote is great, but I'm missing more feeatures. So I'm building a Monitor Assistant (to be accompanied by the Monitor Pilot) with the following features:

• A/B input
• Mute / Dim
• Solo Mid / Solo Sides (M/S)
• Low pass filter (around 200hz)
• High pass filter (around 10Khz)

The features are tailored for mastering with some more specific to vinyl mastering. I've taken a lot of inspiration from KA Electronics designs using the same THAT op-amps for input and outputs stages, and the MS circuit. The filters are not fully designed, but the idea is that they will be on separate boards being easy to be changed. I've routed data signals to the filter connectors for possible controllable filters, but I'm planning for them to be static in the first build.

I want the same remote + controller design as the TC Monitor Pilot, and in my early tests I had success using a 2 meter USB-C cable to carry power and I2C signals between 2 devices. So that's what I'm planning to use. I've been skeptical about the cable length, and I've read many posts and articles about I2C over longer distances, some saying it would never work, while others say it works fine. I had no problems with my test on the breadboard, which is good.

I'm using an Attiny 814 in the remote device, it's the brain with all the logic. It's connected with 3 buttons, each with 2 LEDs, and I'll add support for single and double press actions to support all features. The controller device is using relays to switch the audio signals controlled by an 8-bit I/O expander (PCF8574) over I2C.

In order to program the remote device, I've included a USB to UPDI converter, using the USB-C plug hardwired to a 2P2T switch switching between programming and I2C signals.

Please don't look close at the power supply, I'm currently planning to use cheaper devices from AliExpress with some filters, but it's not set in stone.

I'm not an experienced designer at all. I have an education in electronics, but I haven't used it in 20 years and I haven't designed anything as complex as this, so there might be obvious problems I'm not seeing. Hence this review request.

What I'm looking for:

• Please check design for obvious faults
• Is there anything that looks weird or wrong?
• The filters are connected with 10-pin connectors, is the layout of the pin order good or problematic?
• Anything else I'm missing or not seeing?

Thanks in advance for your time! 🙏

Hi to all,

I just want to make a album for 15 songs time over 16 minutes. It's simple. Each user has to copy and paste adding only one song to the album so in the end it's 12 songs, one per user, and each album has to have a different theme.

Whoever adds the last song of the album gets to say what the the theme for the next album will be and it starts all over again.

Songs over 16 minutes:

1. Pink Floyd - Echoes (23:31)
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.

Hi everyone,

I am planning on building WAW speakers and I am looking for some advice.

Goals & Context
Here is some of the things I'd like to do in no particular order:

• Keep the box relatively small (around 30L max)
• Around 30cm wide baffle max and around 20cm deep (shallow design)
• F3 of 30hz, up to 20khz
• Should work well pushed into corners
• Vented box for the sub for extra extension
• Closed box for the wideband (or better suggestions?)

On a more subjective angle (probably not so helpful, but still including it here). I guess I love a 'vintage' sound that's not boomy in the sense that romantic / coloration is not something that normally bothers me. I want to be able to dream away and drown in the music. Not to say that do not believe in measurements, it's just that a flat response curve is not a particular end goal for me. One of the reasons I wanted this system to have an active XO is to also learn and listen for myself how drivers can integrate to produce a sound I love.

Where I am so far
I've been both drawing up some sketches for aesthetics and playing around with Hornresp to get some feeling for what is possible. Nothing is decided yet but I am aiming for something like below. This particular one is sketched to be 294mm wide, 193mm deep and 770mm. I like this because in my opinion these look 'less heavy' when placed on a stand or legs (which I haven't designed yet), as opposed to a floor-standing tower that reaches all the way to the ground.



So far I've made these decisions:

• Wideband will be Markaudio MAOP-5s
• Subwoofer will be the SB23MFCL45-4
• I'll use a MiniDSP Flex as a digital XO
• Port on the back

There is still lots open. With this thread I am mostly looking for some thoughts and input for further exploration. Not sure how best to approach this, so I think I'll just post the things I am pondering over in separate posts for anyone to shoot at. Starting with...

A Hornresp Rocket?
In Hornresp I currently converged on modelling a vented box for the SB subwoofer with a slight taper, that gave me a response in the 30hz region while remaining the internal volume under 30 L. Here is a few screenshots from one of the configurations I ended up with, just to give you an idea of what I was doing:




Then I started playing around with this configuration and I suddenly ran into this weird configuration where the horn is almost like a rocket. This simulates really well for my purpose and decreased the size of the port somewhat. Not sure if this is something I will do, but I am honestly wondering how this configuration can give such a response? The start of the port feels so incredibly small... Anyone knows what is happening here and if this is something worth exploring further? Some screenshots...

For years I've been pursuing a way of getting better stereo sound like you get when you use a divider wall between stereo speakers to eliminate crosstalk and interference patterns. One way to do this is to add more channels using a matrix. A simple and well known matrix is to turn L and R signals into L-R, L+R, and R-L. What no one has ever told me is that this simple array will do amazing things if you space the speakers apart properly and listen at an appropriate distance. Center panned sounds only play through the center speaker, so there are no interference patterns so that solves the phantom center problem. But what happens when a sound is panned hard to the right or left? For a right panned signal you end up with the array playing a -R in the left channel, a R in the center and another R in the right channel. This of course creates interference patterns, but good ones! They work to create the proper stereo separation and never cause a null to cross our ears! This is because there is a null in the center of the sound field instead of a lobe. So each ear gets an appropriate stereo lobe! Each ear gets a lobe - so punny!

Here's a picture of my current array using basic little Sony SSCS-5 speakers



You can see I'm actually using 5 speakers here. The center channel plays full range down to 100Hz. The inside left and right play down to 600Hz. The outsides play 600Hz and down. This just helps to boost the stereo effect as the wavelengths start to get long compared to the width of the array. 3 speakers works great. 5 just gives it a little something extra and I happen to have lots of speakers and amp channels available.

Watch this video to see how the interference patterns produce excellent stereo throughout a huge range of frequencies. I used Falstadt's great ripple tank simulator to demonstrate how the effect works over a huge range of frequencies. http://www.falstad.com/ripple/Ripple.html. The three dots at the top of the screen represent an appropriately spaced array of 3 speakers playing a hard right panned signal. The circle down below represents the listener's head with strong signal reaching the right ear and weaker signal that is phase delayed reaching the left ear - as it should be. As I play a wide variety of frequencies you can see that strong stereo separation is maintained and no null from interference patterns ever crosses the right ear. You do get some weakening of the signal as the frequency goes down due to the center null widening so you can boost up the side channels in the lower frequencies or add a wider spaced set of speakers for the lower frequencies. I actually do both.

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So what happens with slightly panned signals? The same thing except the lobes are not as different, so no matter the panning there are no unwanted nulls from the interference patterns at the listener's ears.

Also notice what's happening off to the sides - not a lot of energy to light up early side wall reflections.

So how does it sound? I'm elated! It's great! It's not phase-y or weird. The sound stage is natural and oh so clear and smooth with beautiful separation and clarity. It's a revelation. On recordings with wild stereo effects they get really wild like they should. I don't see myself ever going back to a two speaker setup for high quality stereo playback. I tried having the outside speakers playing regular stereo from 600Hz down and it's just a downgrade. This is MUCH better IMHO even in lower frequencies where it looks like it's falling apart and just turning into mono. It's blowing my mind.

As a general starting guideline I recommend spacing the speakers at about 1 foot apart center to center for the 3 center speakers and put the listening position about 8 feet back. You'll hear some good stuff with just 3 speakers but you may need to put a low frequency boost on the side speakers to correct the tone for side panned sounds. You can do this by playing correlated pink noise and panning it left to right. Adjust the lower frequencies on the side speakers until the pink noise sounds similar in tone and volume across left, center, and right of the sound field. Experiment with spacing and listening distance. It's surprisingly flexible.

One difficulty is how to setup the matrix array. I use my Mac mini running Audio Hijack to do it in the digital domain. This allows matrix mixing and access to all 8 channels of my Denon receiver over HDMI. You can do a basic 3 speaker array using a 2 channel playback system by creating a L+R signal for the center speaker and a L-R signal for the side speakers. I run the L+R signal into the right channel, and the L-R into the left channel of the amp. The left channel runs both side speakers in series or parallel. Just wire up the right speaker opposite of the left speaker and it works!
I don't recommend mixing line level signals in the analog domain unless you have appropriate signal mixing hardware that that properly buffers everything. YMMV but my results were lackluster just using Y-connectors. I also don't recommend hooking multiple amp channels up to the same speaker unless you really know what you are doing. If you are using low pass and high pass crossovers on the outboard speakers like I am, watch out for phase reversals. Suddenly your soundstage is backwards!

12/30/2022 Update. After trying a lot of things I'm back to just 3 speakers. With proper spacing and the voids filled in between the speakers to minimize edge diffraction this really produces the purest sound and best imaging. I think I was tricked by the increased overall volume of adding more speakers. So there's something to that. If you have a lot of the same kind of speakers lying around and they can't play very loud, 7 of them playing at once makes a noticeably higher playback level possible than just 2 or 3 of them, and you can get some really great imaging. Turning up the volume a little to make up for the fewer speakers and I'm actually hearing better sound overall. This is great news because it's easier to set up as there are no time delays required and so a simple 2 channel amp and 2 channel dac can be used to power all 3 speakers. You just have to get the stereo signal matrixed into L+R and L-R signals. I heard one person say that the electric summing and differencing causes irretrievable loss of information. It does if you just take the L+R signal by itself, or the L-R signal by itself. But if you mix all the signals, including the inverted L-R, which gives R-L, everything that should reach the ears does. And, much less of what shouldn't.

According circuits and inside images of Naim Audio's NAP250 the main difference to NAP160 and NAP110 is an additional discrete power voltage regulator between rectifier and main capacitors - go to schematics under
https://www.diyaudio.com/community/threads/naim-nap250-original-clone-build-thread.390504/page-2
and the attachments.

If I remember correctly, all three models use the same power amplifier board (also with the same circuit), and the power supplies exists in the following versions:

1) NAP250: single winding on toroidal transformer and two main capacitors for both channels but two voltage regulators for each channel
2) NAP160: single winding on toroidal transformer and two main capacitors for each channel (four pcs. at whole) but no voltage regulators (thus less output power than NAP250)
3) NAP110: single winding on (smaller) toroidal transformer and two main capacitors for both channels - also no voltage regulators (therefore even less output power than NAP250)

For my ears NAP160 (and even NAP110 at low listening levels) sounds better in most respects - probably because of the small (only 10uF) elcaps at the output of (i. e. behind) the discrete serial (not shunt) voltage regulators, it's sonic signature probably affects the overall sound character.
Maybe also due to the fact that the NAP250 (compared to the NAP160) has no separate transformer secundary windings for each channel and therefore the GND management is (and must be) carried out total differently.

To find out this exactly I want to use large elcaps (10mF resp. 10.000uF/63V) also at the output of the voltage regulators of NAP250 (i. e. replace of the small present 10uF caps between voltage regulator and power amp voltage input).
To check this without risk of destroy of the voltage regulator modules additional protect steps (like inrush current limiter for charging while switch-on/diode for discharge after switch-off this caps) are absolutely necessary.

Who had already perform this and which impressions while a listening test were after doing this perceived ?

Please note - everything mentioned above refers to the model series described at the beginning of the 80s (maybe predecessors of olive series) - go to
https://www.avoptions.com/downloads/manuals/Naim-Audio-Brochure-1981.pdf

Even this series I know in different versions:
1) with NPN output power devices from Semelab NA001 "SM3282" (are there a datasheet from Semelab ? - I had only make listening tests with this version, bought in 1981)
2) with NPN output power devices from Semelab "SM8927" (have never heard)
both probably identical to Semelab's BDY58 - go to the attached datasheet
but I don't know exactly.
3) with NPN output power devices from Thomson CSF (later SGS resp. ST) "BDY58" (also have never heard)

some additional URL's:
http://www.acoustica.org.uk/t/naim/power_amps.html
https://www.stereophile.com/content/naim-nac-62-preamplifier-nap-140-power-amplifier
https://www.hificritic.com/uploads/2/8/8/0/28808909/_excerpt-201603-3.pdf
https://m.review33.com/forum_msg.php?db=1&topic=79051010190053&start=190&sort=
https://community.naimaudio.com/t/what-type-of-transistor-is-the-na009/10119?page=3
https://www.diyaudio.com/community/threads/naim-nap-110-amp-high-dc-offset-and-mute-channel.257524/
https://pinkfishmedia.net/forum/threads/faulty-nap-110-help-me-please.150581/
http://art-and-technology.blogspot.com/2016/05/the-naim-audio-game.html
https://www.diyaudio.com/community/threads/nap250-amp-boards-regulator-boards.344855/
https://www.diyaudio.com/community/threads/naim-rebuild-boards-nap-140-and-nac.387889/
https://www.diyaudio.com/community/threads/naim-audio-power-amp-grounding-question.172367/
https://www.stereonet.com/forums/topic/93048-dusty-old-naim-gear-options-for-a-friend/

P.S.: are there genuine service manuals published from that time ?

This is a new project for my friend Mark who has an enormous "great room"
30x52' with vaulted peak ceiling >20' high. The goal is not to fill the entire space with sound but the LR portion, which is about a quarter of the total floor space. Mark seeks a game-ending system, with some financial limits. He also happens to be a master metals fabricator with a lot of skills & tools, which will be brought to play.

I post this as a reality-check / peer-review of my plans.


This pic shows a fraction of the big room.

Initially, Mark wanted scaled-up versions of my LX521 clones with dual 15" SBA Nero-15SW800 in a W-frame force cancellation setup. But after examining the room again, I persuaded him that OB might be too expensive & difficult to achieve 20Hz bass at >100 dB even in just his LR space. I've heard his EV Sentry II & JBL L212 speakers in the space & there's little question the sheer size of the room is a challenge. Amending the acoustics with floating absorbers/diffusers in the ceiling (and elsewhere) is not an option due to WAF. A large rug in the LR is in the works; currently the entire space is reflective.

The current plan is a pair of 12" woofers firing sideways in opposition to each other in a sealed enclosure, topped by an OB lower mid, mid & tweeter. This would be an active system with miniDSP Flex 8 & a mix of amplifiers for the various bands, a turntable, and a Wiim Ultimate streamer/preamp.

The physical design will draw from the iconic Acoustic Research AR9 (1978-82), the modified sealed-bass LX521 I recently made for my son, and the Linkwitz Orion. Mark likes the look of my Orions, which also garner better WA. I believe I can replicate that with side-firing 12" woofers in a sealed box + a WG tweeter to reduce diffraction & control vertical directivity.







The drivers:

Woofer: SBA SB34SWPL76-4 Low sensitivity of 85 dB/2.83V, but 19Hz Fs, a low 79 liters Vas & 0.31 Qts allows 0.7 Q in a 40 liter (or smaller) box, with a slow roll-off easily amended by DSP. Two woofers in a box double that size could easily provide >100 dB to below 30Hz with force cancellation minimizing vibrations to the OB above. 15mm Xmax is excellent, as is the FR claimed in the spec sheet.



Lower Mid: Satori WO24TX -- Since it will be OB & needs to move a lot of air in this big space, I paid attention to Xmax as well as effective piston area. A 12" driver might work better in the lower frequencies (as it will get quite a lot of EQ boost to compensate for the dipole cancellation effects), but this Textreme driver is flat out to 2.5kHz on axis, with little beaming to ~1.5kHz. 8.75mm Xmax is pretty good for a driver like this, and it's an opportunity to find out first hand what a Textreme driver can do. If it can be made to cross well at 2kHz or lower to a WG dome, we might be able to keep it 3-way instead of the usual 4.



High Mid: The Satori MW13TX is a natural choice, given the WO24TX lower mid choice. It will not be necessary if we go 3-way.

Tweeter: My favorite dipole tweeter Aurum Cantus AST2650 will get a shallow waveguide on both sides. The waveguide has yet to be made, but I've seen enough iterations of such that it should not be a big challenge, executed in 3D printing or CNC cut directly in the baffle board.

------------

Tweeter, if 3-way: Satori TW29TXNWG Textreme is a natural. The reviews of the Beryllium WG guide version in both Audioxpress & Hificompass state they are good as low as 1kHz, and there's no reason to believe the Textreme version would be much different. The back tweeter would be the non-waveguide version -- Satori TW29TXN, which is shallow enough not to require cosmetic adjustments for the hole which might end up having to go through the baffle board with the deeper WG tweeter.

One feature that will likely be adopted from the Orion is the mounting of the lower-mid 9.5" driver by its magnet to the top of the bass bin. This config positions the driver on the baffle without touching it, preventing mechanical conduction of the driver's vibrations into the baffle. There's a foam gasket to prevent spurious vibration between the baffle hole and the driver rim. The force cancellation of the bass drivers should keep most of the larger vibrations out of both the box & baffle. This method of mounting the low mid driver will complete the primary anti-vibration scheme.

-

EDIT: Forgot to mention that we'll consider adding one or 2 custom made subs, either like the one I just built with a Nero-15SW800 15" Pro driver, or the SB12" in the main speakers. The main speakers would be treated as subs (because they will be subs) and another 1 or 2 subs added to the sides of the listening area. A challenge is power outlets on one side only.

Hello everyone!
I've recently finished my vintage inspired 2-way design and figured I'd share the journey here for any fellow members who may be interested in the concept or even building it for their self.

Soooo. Let's see it! What is it? Kronos is a sealed 2-way design utilizing the SEAS A26RE4 10inch Woofer and the Visaton FRS 5x-8 2inch in a WG.



Wait, isn't that Visaton driver a full range? Isn't this more of a "WAW" design? Yes, the Visaton is in fact a full range driver but it's actually being utilized as a tweeter in this design. It's mounted in the Visaton WG and integrates perfectly here with the SEAS woofer.

Isn't there already a similar design for this woofer? The A26? Yes, there is. However the tweeter for that design is rather pricey at $350+ each, while the cost here is $14 for each driver and around $19 for each WG currently on Parts Express. (Other options available as well, see below)

Okay okay, enough with the Q&A, let's get into how this came about and details of the design.

Introduction:

The Kronos speaker build was born from a sense of nostalgia—rooted in childhood memories of sitting in front of my dad’s hi-fi system, mesmerized by the towering loudspeakers that filled the room with sound. Those classic designs, with their large woofers and cone tweeters, left a lasting impression. They had a presence—both visually and sonically—that felt larger than life. With Kronos, I set out to pay homage to that era and those experiences, blending the soul of vintage loudspeakers with the clarity and control of modern design. It’s a tribute to the sound that sparked a lifelong passion.

Driver Selection:

To bring the Kronos concept to life, I carefully selected a driver lineup that reflects both the spirit of vintage design and the performance of modern components. For the low end, I chose the SEAS A26RE4, a 10" paper-cone woofer known for its rich tone, effortless bass, and smooth upper response. It’s a direct nod to the classic wideband woofers of the past—capable of anchoring the system with warmth and authority.


For the top end, I went with a more unconventional approach: the Visaton FRS5X, a small full-range cone driver, paired with the Visaton WG 148 R round waveguide. This combination offers a controlled dispersion and a pleasantly natural tone that echoes the voicing of vintage paper cone tweeters, but with improved focus and clarity. To mount the FRS5X, I simply centered it on the waveguide and drilled my own holes—an easy but effective way to create a tweeter solution that stays true to the DIY spirit and captures the character of old-school designs.


Worth noting: With the rise of 3D printing and modern fabrication techniques, custom waveguides for drivers like the Visaton FRS5X are now readily available. For those looking for a more refined or drop-in solution, Heissmann Acoustics offers a purpose-built 3D-printed waveguide specifically designed for the FRS5X. It's a great option for builders who want to simplify the mounting process while maintaining the same compact format and controlled directivity.



Enclosure Details:

The SEAS A26RE4 woofer is housed in an approximately 85-liter (about 3.0 ft³) sealed enclosure, giving it ample volume to breathe and deliver deep, full-bodied bass with natural roll-off—true to the character of classic hi-fi systems. This generous internal volume helps the woofer operate efficiently without excessive low-end boom, maintaining a balanced and effortless presentation.


The Visaton FRS5X is isolated in its own 1-liter (0.035 ft³) sealed chamber. This small compartment ensures that the mid/tweeter remains unaffected by pressure changes from the woofer, allowing it to perform cleanly and consistently.


Throughout the cabinet, adequate internal bracing was incorporated to minimize panel resonance and structural flexing. The result is a rigid and acoustically inert enclosure that supports clean, undistorted output even at higher playback levels.



Crossover Details:

The Kronos crossover began as a theoretical layout, designed with target values based on driver behavior and desired voicing. From there, it was refined entirely by ear, with countless hours of listening and adjustment until the final values locked into place. This process allowed the system to reach a balance that felt natural, dynamic, and emotionally engaging—true to the character I set out to achieve.


The SEAS A26RE4 woofer, a modern version of the W26 used in classic designs like the Dynaco A25, has a naturally smooth roll-off that doesn’t strictly require filtering. That said, I chose to add a small 0.33 mH series inductor to gently tame the upper midrange, making the speaker more forgiving and enjoyable at higher volumes—reducing the risk of harshness or “shouting” without robbing it of presence.


For the FRS5X tweeter, mounted in a waveguide, no series resistor was needed. The waveguide not only improves sensitivity and dispersion control but also helps the FRS5X blend naturally with the woofer. Without the waveguide, I would have added around 1 ohm of series resistance to balance its output. The high-pass network is essentially first-order, using a capacitor for the main roll-off. A parallel inductor was added to keep the tweeter’s upper resonance from bleeding through—simple, but effective.


While a textbook solution might call for an RCL (resistor-capacitor-inductor) network for perfect impedance correction, I found that in practice, a single coil did the job just fine. An optional overall impedance compensation network was included for the sake of completeness, but it's more a nice-to-have than a necessity in this build.


In the end, the crossover reflects the spirit of the whole project—minimalist, purposeful, and guided by listening above all else.

CROSSOVER PCB:

To make this project more accessible for others—especially those new to DIY loudspeakers—I went a step further and designed a dedicated PCB for the crossover network. Rather than relying on point-to-point wiring or a perfboard layout, this custom PCB ensures clean, repeatable assembly and proper part spacing, helping reduce the chance of wiring errors and making the build experience more enjoyable.


The board is laid out with component footprints matched to the actual values used in the final design, and it includes clear labeling for easy reference. Whether you're a first-time builder or a seasoned DIYer, this PCB simplifies the process and makes it easier to achieve consistent results.


I’ll be including a download link at the end of this presentation with everything needed to build your own pair of Kronos speakers—including crossover schematics, PCB files, enclosure plans, and additional notes gathered throughout the build.



Finished Speaker:

Here’s a look at the finished Kronos speaker. Aesthetically, I realize this look might not be for everyone—but that was never the goal. I wanted the finish to reflect the spirit of the project: cheap, fun, and bold. The result is something unique, eye-catching, and artistic.


I’ve had a few people ask how I achieved the finish, so here’s a quick breakdown:

• I started with a roll-on bedliner called "Total Coat" to create a tough, textured surface.
• After that, I applied a Rust-Oleum yellow paint as the main color.
• For added visual interest, I used Rust-Oleum Black Marbling spray, which creates a random web-like texture and gives the surface a more dynamic, artistic feel.
• Finally, I sealed everything with a Rust-Oleum matte clear coat, which helps protect the finish and reduce glare.

It’s not a high-end veneer or mirror-gloss lacquer—but for a fun, rugged speaker with personality, it gets the job done. Cheap, effective, and satisfying to see come together.



Final Measurements:

Below you can see the final measured response of the Kronos design. The results highlight just how well the Visaton FRS5X in a waveguide and the SEAS A26RE4 woofer integrate—especially considering the simplicity of the crossover network.


The response is impressively smooth, with excellent tonal balance and a natural transition between drivers. The waveguide not only improves the FRS5X’s efficiency and dispersion but also allows it to blend seamlessly with the larger woofer, avoiding the typical disconnect you might expect from such different-sized drivers. The minimal crossover does just enough to shape the response where needed, while preserving the raw, engaging character of the drivers.


This measurement validates the listening impressions—a coherent, dynamic speaker that stays true to its vintage inspiration while performing with modern finesse.

Listening Impressions:

The final implementation of the Kronos exceeded my expectations. While I didn’t build these to be the ultimate reference monitor or the “end-all-be-all” speaker, the result is something that sounds exceptionally good—better than I had originally imagined.


The bass performance is particularly impressive, with deep, full extension that's further enhanced by room gain and proper placement. The SEAS woofer really shines here, delivering weight and authority without muddiness.


Tonally, the speaker holds up well across a wide variety of genres. So far, I've enjoyed everything from Rock, Jazz, Pop, Hip-Hop, EDM, to Classical, and the system has handled them all with confidence. The highs are clean without being harsh, mids are clear and natural, and the overall balance feels cohesive and engaging.


Even at very high listening levels, the speaker maintains its composure, with no sense of strain or collapse—perfect for those nights when you just want to crank things up and let loose.


I’ve also had a few friends over to hear them, and the reactions have been consistently surprised and impressed. There’s something satisfying about watching someone sit down with no expectations, and then light up the moment the music starts.

In Conclusion:
The Kronos has accomplished everything it was designed to do—and then some. It’s a speaker that brings together nostalgic inspiration, modern performance, and hands-on DIY fun in one cohesive package. I’m genuinely proud of how it turned out, and I know I’ll be enjoying these speakers for many years to come.


For those interested in diving deeper into the design—or even building a pair yourself—I’ve put together a comprehensive resource link below. This presentation has only scratched the surface, and the download includes detailed plans, crossover files, PCB layout, measurements, and more.


If you have any questions or run into issues, don’t hesitate to reach out. I’m always happy to help fellow builders in any way I can.


Thanks for taking the time to check out my project—I hope it inspires you to build something of your own.

LINK TO KRONOS BUILD PLANS: https://drive.google.com/drive/folders/1Kpa-w3JEGQmEdG6RKKRCQnM0pMenjgjl?usp=sharing

I wanted to start a thread so members can show off their DAC creations. 🙂

They sound, but to hear them and with an obvious problem in the medium-low range, you have to turn up the volume a lot. a lot!
is there any chance that they can be recovered? they asked me if I want to take them back at a price... but
I wanted to know from you if they are repairable and how complicated they are to fix.

dynaco sca35 - having an output transformer rewound - should i do both?

Hey, Michael here from Sydney, Australia. being music lover for many years, come across issues with turntables and amplifiers, would like to learn and seek advice and sharing experience from fellow members.

I realised the other day that while I know many of the milestone points in amplifer design (Loftin-White, Williamsone, JLH etc) I have no idea of the history of the classic complementary AB transistor amplifier (as typified by the 741 op-amp)
a) first proposed complementary bipolar AB (or class A)
b) first successfully implemented it as an audio power amp
c) first used the venerable 2N3055/2N2955 pair in a product

Was it NatSemi or Philips? Or someone in Japan? Even "The Art" just assumes it is too obvious to bother attributing the design to someone.

Pre-BAF appetizer project posted. Enjoy 🙂

Build This MoFo!

EDIT: (6L6, Jan ‘23) above link is dead, here is link to the article - https://6moons.com/audioreviews2/mofo/mofo.pdf

Hope to see you at BAF! Don't forget admission is free for everyone who brings a project.

Let us know what you're bringing in in this thread:

What are you bringing to Burning Amp 2017?

IMPORTANT NOTE: A Zener diode from the MOSFET Gate to Source is needed to protect the MOSFET from inductor "kickback" I got away without this when using MOSFETs with high maximum VGS and lower supply voltages, but had not anticipate the range of FETs, inductors, and supply voltage that might be used. Even when the stars align, it's too close to not consider the Zener mandatory.

There's already a place for this diode on the PCB sold here in the store. When my stars align, I'll update the article pdf.

In the meantime, my good mentor PRR has provided some illustrative filler:
https://www.diyaudio.com/forums/pass-labs/313649-build-mofo-279.html#post6368030

Dear Community,

I recently watched a video about the B&C coaxial compression drivers. After looking them up i was shocked how pricey they are. Then i thought: can't we make our own coaxial compression driver with conventional cheap drivers/parts?
When thinking about the concept i became more and more excited to try.
Directivity control provided by a horn + point source behaviour like a full range/coaxial driver = why not?

Let's discuss the possibilities and try to succeed!

Hello,

Since the Pass forum uses massive heatsinks and folks don’t mind miscellaneous questions, here’s mine.

I was recently given a few massive heatsinks and looking for recommendations on how to cut them (it’s DIY isn’t it 😀) since a few are too tall. They are similar to the Heatsink USA stuff but slightly more robust.

Heatsink USA :


Mine are also about 10” wide but the rest is different;

Heatsink USA plate is 0.375” (9.5mm) thick , mine are 15mm thick. Heavy like hell 😀

Heatsink USA total thickness with fins is 2.875” (73mm), mine are 83mm.

Based on hands on experience, how would you cut such an aluminum piece so it’s usable, imperfections isn’t an issue, ugly side would be at the bottom, no problem.

Picture below;


Thanks for your help 👍

P.s. I also received some more that are insanely massive but I will keep it for a future thread.

Hi. The plan for my tubelab SE was to fill the role of HF amp in my 3-way tri-amped system. The amp sounds great but unfortunately, the gain is 7.5dB less than my LF and MF amps.

Rather than continuing to sacrifice 7.5dB of gain in the LF and MF in my crossover, I’ve been looking at ways of increasing the gain of the tubelab SE.

Any alternative needs to be a single 9-pin noval tube so I don’t have to go changing the metal work.

I’ve done some modelling in LTSpice with a 12AX7 running at 1mA, parallel 12AX7s with 1mA each, and with the 12AX7s configured as a mu follower. Ignore for now that 1mA would require a different CCS.

Here’s the gains and distortions for 0.1W out and 1W out.





According to the simulation at least, the 12AX7 mu follower looks to be a good option, apart from the upper stage needing heater elevation.

Is there anything I'm missing? As a high-transconductance tube, I suspect the 5842 was used in the first stage for good reason.

Any other suggestions?

Thanks!

This weekend I found termite droppings on the floor underneath my mid/hi speaker box. I thought I got rid of the termites when I disposed of my old TL sub woofer but apparently they migrated to the mid/hi enclosures.
The enclosures are constructed of Okoume plywood. This plywood is not water resistant. I can wet it, but not for too long a time. These enclosures are simple small bass reflex boxes of about 30x30x15 cm. Easy to replicate with water resistant plywood. But not as nice to see.
The new TLs I sprayed with "Ortho Home Defense Termite & Destructive Bug Killer" before assembly. I have no signs of termites yet, but that doesn't guarantee they are not infested.
I am really worried about the termites migrating to my new TL subs which are much larger and harder to rebuild. So preferable I treat both the small enclosures and the TLs equally. The first first to expunge, the second to prevent.
Any ideas of how to treat for termites? Since the speakers are in a dry room, part of the time air conditioned, no moisture, I assume these are dry termites. I never see a sign of the insects or wings. Only excrements. There are no environmental or import restrictions on any chemicals. As long as I can purchase from Amazon.

Good afternoon from Brisbane Queensland Australia. Thanks for accepting me, I have a long-standing interest in sound Hi-Fi, both valve and solid state. I'm sure this + will help me. Enormously with the collective knowledge that I'll find here.
Other Hobbies include motorcycles of which I have four, travel, music in general. Good food and wine.

I am considering assembling this 2E26 amp, what is your opinion on it:

https://www.r-type.org/articles/art-271.htm

Introduction:
Hey guys, been a long time lurker here. I've been pretty busy lately working on a dirt cheap unity horn project for my desktop setup. The entire horn is going to be 3D printed for ease of assembly. A lot of effort has been put into making this build as cheap as possible. I actually think this might be one of the cheapest unity horns out there. I have two goals I want to achieve for this project.

1. Wide phantom image and constant directivity. I have lots of pc-monitors in-between my current speakers. The problem with this is it forces my speakers to be very far out from the listening spot (around 150 degrees). Unless you are seated perfectly between the speakers, the sound-stage collapses. It is my belief that a wide CD horn will fix this.
2. Provide an affordable MEH so that more audio geeks can hear these awesome speakers. I really love unity type speakers, the linear phase, constant directivity, and acoustic filtering provide a lot of benefits that are hard to achieve otherwise. My dream is to eventually make this into a diy kit, but I'm not sure if I have the resources to make this a reality.

Woofers:
This all started when I discovered these little Dayton TCP115 woofers. I was working around in hornresp and pasted the driver profile by mistake. Low and behold, the simulation had an extremely wide bandwidth for such a cheap driver. The high xmax is also nice for going low so I was able to make this design a 2 way and still get decent bass.

Tweeter:
Most, unity horns seem to use compression drivers. Since I don't need high output and need a cheaper option I decided to go with something different. The XT25 is what I am using for now and it seems to work quiet well. By using a really large horn I was actually able to push the crossover frequency quiet low (around 1.2khz). I know, I know, that crossover is insanely low for this tweeter. I have more data on why this works; will post more later. Right now I am having trouble getting accurate distortion measurements to confirm my theories.

Measurements:



Around 15 degrees off axis after some quick EQ. The dips at 6k and 10k appear to be from a problem at the throat which are being fixed in the next version. The next box is also going to have a flush mounted horn and 18mm round overs on the baffle. I am hoping this will improve those ripples. You can't just EQ those ripples at any one angle. As you can see the dips move around depending on your angle off axis.



1/3 smoothing of the same graph. I don't know what the exact angles are, it's really just a proof of concept to show the directivity is being controlled. The light green line is around 60 degrees, which is why it is so low in level.

Things I still need to do:
Throat optimizations, active xover tweaking, passive xover development, take more accurate polars outside, measure below 200hz, port it (maybe?), make it pretty.

After listening tests of my pre standard II JFET preamplifer, and upon requests of the builders, I have decided to design a new version of the Dipre 2 preamplifier, Dispre 2 - JFET.

The main difference is that Dispre 2 – JFET has Toshiba 2SK170/2SJ74 devices in the input stage, not the bipolar transistors that were used in the Dispre 2 V4. This modification resulted in a design of a new PCB board, as it was impossible to simply replace BJTs by JFETs, circuit modification of the input stage had to be made. At the same time, I added two resistors to enable setting of the output stage idle current. These resistors allow, in case of high technology spread of output devices, to tune output stage idle current.

Dispre 2 – JFET can be also used as a headphone amplifier, without any components changes needed.

Dispre 2 – JFET has complementary differential circuit topology with self biased JFET input stage (this topology was introduced by John Curl). This maximizes linearity of the input stage and distortion suppression does not rely only on an overall negative feedback. To remove output DC voltage component, DC servo is used.

Output stage idle current is set at 40mA, and it works in a class A up to 8V into 100 ohm load. For standard link load 600 ohm and higher, the output stage works in a class A for the whole range of output voltage up to clipping.

Dispre2 - JFET has wide bandwidth and high slew rate again, similarly as Dispre 2 V4.

Regarding PCBs, please visit a thread here:

https://www.diyaudio.com/forums/vendors-bazaar/166049-dispre-ii-pcbs-available.html

or check my webpage:

https://pmacura.cz/dispre2-jfet_en.htm

Hello all. I have been trying to get a small soundsystem together for a while, without being able to make much traction on the project. Mainly due to time constraints and a lot of muddle over the config of such a system. I made many plans and acquired a bunch of parts and equipment for the new system, but it has been difficult to find an optimum due to the following requirements

Extremely portable, to flight ready
Weather resistance, some marine environment ability required
A bit of independence ability from fixed power points
Bass heavy sound
Wireless where able
Multizone compatibility
Live mics and instruments ability
Karaoke
The music is classic and modern Bollywood and West Indian

It took a while for me to note that where I needed environmental protection, the gig was smaller and with a much smaller range of inputs. I have decided to make it a pool of gear that I can mix and match for my needs. I have also had to consider some ready rolled gear instead of all DIY to neatly meet the requirements

Speakers
This is where I am trying something different. The JBL BB3 has sufficient output for the smallest gigs that I do. I acquired a Zealot S89, which appears to be similarly built as the BB3 and contains the same Racer8 driver that I have been messing with. The internal speaker setup is 2.1 with the mains section containing tweeter and midbass two-ways. I have been trying this one out over the last few days and the output is tremendous for something this small. The sound is clean and bass is forward and powerful. Battery life is impressive too. From full charge, the unit lasted a night, day and a night before turning itself off. This was at my regular indoor listening levels. Charge time seems good. My laptop USB-C charger works very well. I timed 6hrs charging time with a regular 5v2A charger and the laptop charger was lot faster, but I wasn't home to get the exact number this time







As is, the S89 will be ample for the porch, garage, deck and boat deck parties. No wires to tape up, trip up on, or pack and unpack. This connects to one of the BT TX fobs. This unit will face me as monitors while supplying the bass for the rest of the BT system. For the mains, I have bought two Zealot S97 units. These will face the floor and connect to the second BT TX fob and operate in TWS with each other. The S89 will be either used on the DJ desk or on the floor in the floor play area if I am mixing a baithak crew. This is a stop gap until I have a better solution here. Anyone who followed my Club Sandwich attempt will be familiar with this issue

I have picked up a further Zealot S51 pair to use as desk monitors for when I have the S89 on the floor. I have to get one more BT TX fob to add the console's headphone out to connect to these in TWS. One end of these speakers is designed as a base to stand the speaker up. It also contains a downward firing PR as well as an upward firing PR on the other end. Btw, the other models also contain dual PR units. I have some red stretchy nylon fabric and sew up some drawstring rucksacks for these speakers. They fit will in my booked of 4x 23kg and 4x 7kg luggage allocations. These are 100L heavy-duty duffels except for a couple of hard shells for the electronics in 7kg carry on allocations. The gear doesn't take up all of those bags

In an earlier attempt, I picked up a pair of DS18 Pro-zt69 coaxes. These are quite efficient, and I am considering tapping the tweeter and woofer wires from the S89 to drive the coaxes as active two-ways. I am reasoning that the powerful lil amp and battery inside the S89 will drive the coaxes a lot louder. To this end, I have been preparing a pair of cabs for the coaxes. I have a pair of SBA racer type PR units that may suit these cabs and coaxes too for a 60-70hz tune. At the moment the cabs are sealed types and 11L internal volume each

For external subs, I am considering a PA 18 with 4R+4R DVC and neodymium mag to reduce weight in a custom composite cab. The subwoofer amp inside the S89 sees a 2R load from a very inefficient driver. I hope that I am correct in reasoning that I can get much louder output with an 18 with coils in parallel. Tuned to the same 40Hz or so as the S89, so as not to upset any DSP filters already in use in that

If I am careful with the tapping, I should be able to retain most of the weather resistance of the unit for when it is used as is and with external speakers, I am hoping for much greater output




For local use with mains power supply, the external speakers will run off proper class d power amps. These are already acquired too

Experimental stuff
The 18" external sub thing will happen later on. Along with the coaxes, I am also building a cab for my DS18 ZR12.4D driver. This is not quite as huge as the ZXI 12" but still substantial. Will fit in my baggage allocations too for the trip coming up. For this trip, I will AB the Zealots vs the coaxes+ZR12.4D. Won't tamper with the Zealots just yet, so will run the external speakers with class d modules



The sources
A Dynabook Protégé for laptop. A Roland DJ-202 as controller and Serato DJ pro with full plugins and expansions bundle. A two into one wireless mic pair for the mic input on the DJ-202. This is my basic source setup for DJ, remix and karaoke

A Yamaha MG12XU console for accommodating more mics and instruments. A further one to one wireless mic pair for vocals from the console. This lot of flight ready sources are topped off with an Akai MPK Mini Mk3 Plus for some keys to complement the Roland TR drums built into the DJ-202

For local use, a Roland JDXI synth and a Roland MX-1 mixer completes the set

I have added two Bluetooth transmitter units to this lot. They are placed on the main and monitor outs of whichever mixer is feeding the PA

Party gear
A fog machine/disco light combo. UV black lights. LED party lights and rope lights. UV reflective backdrops. Projector and screen. Stand for mounting projector and lights

Support gear
Two powerbanks with fold out solar panels. Another pair of smaller powerbanks for the LEDs. USB hub with multiple monitor support. Laptop USB-C charger for the car to top all the things up as backup

I am sure there are some things that I am forgetting to list or missed entirely

Hello members,

There have been several queries regarding using Class-D amplifiers for driving AC turntable motors, often of the synchronous type. I would therefore like to show a few simple methods for obtaining decent results using a 3-phase motor. These methods, starting from a square waveform, use Selective Harmonic Elimination (SHE) and other cancellation techniques that, along with an LC filter, provide low distortion sinusoidal waveforms with lesser electromagnetic interference (EMI) compared to the high frequency PWM used by class-D amplifiers. The techniques used here are very well understood, and in use by the power industry for decades. I shall also share some of the significant published literature on the topic for those interested in the 'details'.

Some of the features of the presented methods are:

• Open-loop drive for all kinds of sinusoidal flux synchronous motors - wound-field / separately excited, permanent magnet or reluctance types.
• Suitable for large / small motors with no changes to underlying philosophies.
• Suitable for star, delta and open-ended winding motors.
• Only two level inverters are used in these methods (though the final phase voltages may have multiple levels). These could be implemented using half-bridge / Class-D modules available in the market.
• Minimal switching transitions give reduced EMI and switching losses when compared to high frequency PWM.
• Guaranteed elimination of all selected harmonics (according to the method), for lower acoustic noise and torque ripple necessary for turntables.
• A single DC bus voltage is used wherever possible.
• MCU implementation requires only counters and GPIOs, without the need for DAC or PWM modules.
• Accurate timing / speed control is obtained using a MHz crystal with the possibility for storing the timing information for various record speeds when implemented on MCUs.

NOTE: These 3-phase methodologies are not suitable for single-phase motors due to the triplen frequency currents (and loss in performance) that would result.

Thanks.

Certainly the seminal figure of my era:

I can remember their appearance on the Ed Sullivan show. Brian's music reverberated on the AM radios at the swimming pool of my teen summers.

https://www.nytimes.com/2025/06/11/arts/music/brian-wilson-dead.html

Brian Wilson, who as the leader and chief songwriter of the Beach Boys became rock’s poet laureate of surf-and-sun innocence, but also an embodiment of damaged genius through his struggles with mental illness and drugs, has died. He was 82.

His family announced the death on Instagram but did not say where or when he died, or state a cause. In early 2024, after the death of his wife, Melinda Wilson, business representatives for Mr. Wilson were granted a conservatorship by a California state judge, after they asserted that he had “a major neurocognitive disorder” and had been diagnosed with dementia.

On mid-1960s hits like “Surfin’ U.S.A.,” “California Girls” and “Fun, Fun, Fun,” the Beach Boys created a musical counterpart to the myth of Southern California as paradise — a soundtrack of cheerful harmonies and a boogie beat to accompany a lifestyle of youthful leisure. Cars, sex and rolling waves were the only cares.

That vision, manifested in Mr. Wilson’s crystalline vocal arrangements, helped make the Beach Boys the defining American band of the era. During its clean-cut heyday of 1962 to 1966, the group landed 13 singles in the Billboard Top 10. Three of them went to No. 1: “I Get Around,” “Help Me, Rhonda” and “Good Vibrations.”

At the same time, the round-faced, soft-spoken Mr. Wilson — who didn’t surf — became one of pop’s most gifted and idiosyncratic studio auteurs, crafting complex and innovative productions that awed his peers.

“That ear,” Bob Dylan once remarked. “I mean, Jesus, he’s got to will that to the Smithsonian.”

Mr. Wilson’s masterpiece was the 1966 album “Pet Sounds,” a wistful song cycle that he directed in elaborate recording sessions, blending the sound of a rock band with classical instrumentation and oddities like the Electro-Theremin, whose otherworldly whistle Mr. Wilson would use again on “Good Vibrations.”

“Pet Sounds” was a commercial disappointment upon its release, but the technical sophistication and melancholic depth of tracks like “God Only Knows” and “I Just Wasn’t Made for These Times” eventually led critics and fellow musicians to honor it as an epochal achievement. In both 2003 and 2020, Rolling Stone ranked “Pet Sounds” No. 2 on its list of the greatest albums of all time. (No. 1 was the Beatles’ “Sgt. Pepper’s Lonely Hearts Club Band” in 2003, Marvin Gaye’s “What’s Going On” in 2020.)

“It was ‘Pet Sounds’ that blew me out of the water,” Paul McCartney once said. “I figure no one is educated musically ’til they’ve heard that album.”​

Hailed as a master hitmaker while in his early 20s, Mr. Wilson soon showed signs of instability. Some of his behavior, like placing his piano in a giant sandbox inside his Hollywood Hills home, might have seemed the foibles of a coddled celebrity.
Brian Wilson: 12 Essential Songs
June 11, 2025
But in following up “Pet Sounds,” he stumbled. Over months of sessions for an album he intended to call “Smile,” Mr. Wilson indulged his every eccentricity, no matter how expensive or fruitless, and his growing drug habit fueled paranoia and delusion. Recording a song called “Fire,” he outfitted studio musicians in toy firefighters’ helmets and placed a smoldering bucket in their midst. When he later learned that a nearby building had burned down at about the same time as that session, he scrapped the track, spooked by the thought that his studio “witchcraft” was responsible.

Abandoned by Mr. Wilson, “Smile” entered rock lore as a lost document of a brilliant but troubled mind. Mike Love, the Beach Boys vocalist and longtime foil of Mr. Wilson’s, called it “a whole album of Brian’s madness.” It remained unfinished for nearly 40 years.


“And how did you come up with so many hits? How did the Beach Boys do it?” “Well, we, we just kept plugging away, kept trying, and we went through a bad period. We fought through it, and then we jump onto a new one.” “It means, it just means that I’m an icon. An icon.” “I started out with, like, I think. Doo doo doo doo doo doo, California girls, you know? That’s how I wrote that. First with a bass line, then the chords, then the melody and then the lyrics after that.”


Brian Wilson, leader and chief songwriter of The Beach Boys, wrote several hits in the 1960s, a musical counterpart to the myth of Southern California as paradise.CreditCredit...Paul Natkin for The New York Times
“I had a helluva time getting through some of the frustrations that go along with being a successful record artist,” Mr. Wilson told The New York Times Magazine in 1988. “When I got out there with the Beach Boys, at first I was OK, because I was riding a wave, riding a crest. But then, later on, 10 years later, I got scared, and I got lost, and I was eating caramel sundaes for breakfast. I was all out of whack!”

After “Good Vibrations” in 1966, the band did not have another No. 1 single until “Kokomo” in 1988, which was made without Mr. Wilson’s involvement.

Mr. Wilson’s life story came to be portrayed as a struggle to escape from the yokes of two men: his abusive father and a controlling psychotherapist, Eugene Landy. Mr. Landy’s unorthodox methods, which included monitoring Mr. Wilson 24 hours a day and padlocking his refrigerator, were effective in nursing Mr. Wilson back to health during two periods of treatment in the 1970s and ’80s. Yet Mr. Landy also went into business with his patient, sharing copyrights with Mr. Wilson and taking writing credits on some of his songs.
Image

Mr. Wilson in 1977 with Eugene Landy, his psychotherapist. Mr. Wilson’s life story came to be portrayed as a struggle to escape from the yokes of two men: his abusive father, Murry, and Mr. Landy.Credit...Mark Sullivan/Contour by Getty Images
Mr. Landy eventually came under the scrutiny of the California authorities and surrendered his license. After an intervention by Mr. Wilson’s family, a court order also blocked Mr. Landy from contact with Mr. Wilson.

Mr. Wilson spoke openly about his struggles with mental illness, including his experience with schizoaffective disorder, a condition characterized by hallucinations and delusions. The condition led to the conservatorship granted to his business associates in early 2024.

Starting in the late 1990s, Mr. Wilson undertook a series of concert tours that celebrated his Beach Boys work as a treasure of American song. Onstage, he often sat at the piano with a blank expression, and in public statements he could seem as guileless as one of his melodies.

How The Times decides who gets an obituary. There is no formula, scoring system or checklist in determining the news value of a life. We investigate, research and ask around before settling on our subjects. If you know of someone who might be a candidate for a Times obituary, please suggest it here.

Learn more about our process.
At the Beach Boys’ Rock & Roll Hall of Fame induction in 1988, he described his ambitions: “I wanted to write joyful music that would make other people feel good.”

Brian Douglas Wilson was born on June 20, 1942, in Inglewood, Calif., to Murry and Audree (Korthof) Wilson. His father was a heavy-machinery salesman who had collected a handful of credits as a frustrated songwriter. His mother, a homemaker, kept the Beach Boys’ books in the early days of the band.

The family moved to Hawthorne, another working-class corner of Los Angeles County, when Brian was a toddler, and had two more boys, Dennis and Carl.

From a young age, Brian was almost completely deaf in his right ear. He gave various explanations for the condition, citing a blow from a neighborhood boy or, in some tellings, his father.

Mr. Wilson in Los Angeles in 1965, at the height of his Beach Boys fame. Credit...via Michael Ochs Archives/Getty Images
As a teenager, Brian was a fan of Chuck Berry’s rock ’n’ roll but was especially entranced by the close, melting harmonies of the jazz-influenced vocal group the Four Freshmen; he led his brothers in careful recreations of their songs.

By 1961, the three Wilson boys were playing rock music with Mr. Love, a cousin, and a schoolmate of Brian’s, Al Jardine. In the band’s most familiar early lineup, Brian played bass, Dennis was on the drums, Carl and Mr. Jardine played guitar, and they all sang.

Around that time, Dennis began surfing and delighted in the fashion, trendy lingo and carefree lifestyle that went along with it. One day he told Brian and Mr. Love, “You guys ought to write a song about surfing.”

They did, and that fall, after a rehearsal while the Wilsons’ parents were out of town, the group recorded its first song, “Surfin.’” The young men called themselves the Pendletones, after a type of flannel shirt popular among surfers. When they received the finished record, released by a small local label, Candix, they discovered that they had been renamed the Beach Boys.

“Surfin’” was a crude blueprint for what would become the Beach Boys’ signature sound: a simple lead vocal line (sung by Mr. Love) accompanied by sunny harmonizing, doo-wop-style scatting and a rudimentary rock beat. To that point the surf music fad had primarily involved guitar instrumentals, but by adding vocals the Beach Boys created a wave rider’s credo:

Surfing is the only life, the only way for me
Now come on pretty baby and surf with me

Click to expand...

Though Mr. Wilson embraced the youthful freedom that surfing represented, he never took to the sport. “I tried it once and got conked on the head with the board,” he once said.

Image

The Beach Boys in 1964. From left, Al Jardine, Mike Love, Dennis Wilson, Brian Wilson and Carl Wilson. Credit...RB/Redferns, via Getty Images
Signed by Capitol Records in 1962, the group was prolific from the start, releasing 10 studio LPs through 1965. With short hair, toothy smiles and matching striped shirts, the young men cut a wholesome image. Their harmonies, shared by all the members, were vivacious and pristine.

Mr. Wilson became the band’s primary producer and songwriter, and his sophistication soon shone through. “Surfer Girl,” a lilting, harmony-drenched ballad that went to No. 7 in 1963, was perhaps the first pop hit written, arranged, produced and sung by the same person.

Mr. Wilson’s first No. 1, however, came as a writer of Jan and Dean’s song “Surf City” (1963). In a sign of conflicts to come, Murry Wilson, who managed the Beach Boys and controlled the band’s songwriting copyrights, was furious that Brian had given a valuable hit to another act.

Other problems surfaced. “Surfin’ U.S.A.” resembled Chuck Berry’s “Sweet Little Sixteen” a bit too closely, so Berry’s name was added to the credits, and his publisher acquired the song’s copyright.

In December 1964, Mr. Wilson married Marilyn Rovell, who sang in a girl group called the Honeys. A few weeks later, just before Christmas, he had a panic attack on a flight to a Beach Boys engagement in Houston and decided to quit touring to concentrate on songwriting and recording.

That same year, the group fired Murry as manager. He responded by promoting a Beach Boys copycat group, the Sunrays, which quickly flamed out.

As Mr. Wilson would recount, his father had long tormented him physically and emotionally. In one form of punishment that Mr. Wilson described many times, his father would remove his glass eye and force his terrified son to stare into the empty socket.

“My dad was violent,” Mr. Wilson wrote in a 2016 memoir, “I Am Brian Wilson,” written with Ben Greenman. “He was cruel.”

Freed from his father’s control and the Beach Boys’ touring demands, Mr. Wilson immersed himself in the studio. For a time, he embodied the role of a visionary working within the confines of commercial pop, much like the producer Phil Spector, Mr. Wilson’s hero.
Image

The Beach Boys performed on “The Ed Sullivan Show” in September 1964.Credit...CBS Photo Archives, via Getty Images
“Pet Sounds,” released in May 1966, elevated the Beach Boys’ music to a level far above anything they had created before. With the rest of the group on the road, Mr. Wilson made the album primarily with studio musicians, and he employed a broad sonic palette: French horns, strings, timpani and playful sound effects like bicycle bells, all in addition to the standard rock complement of guitar, bass and drums.

Songs like “Wouldn’t It Be Nice” and “Caroline, No” explored themes of lost innocence and the transition to adulthood. Most were written with Tony Asher, a young lyricist and jingle writer whom Mr. Wilson had recently met. Mr. Wilson took painstaking care with every detail of the recording, including lushly arranged stacks of vocal harmonies, which for the other Beach Boys often meant an excruciating number of takes. Mr. Love called him “the Stalin of the studio,” only half in jest.

Upon release, the album stalled at No. 10, a relative dud by Beach Boys standards. By then, however, Mr. Wilson was already working on his next gem: the single “Good Vibrations.”

Spliced together from months of sessions across four studios — according to Mr. Love, the group recorded 25 to 30 vocal overdubs for a segment that lasted just five seconds — “Good Vibrations” was a catchy and sonically adventurous invocation of peppy West Coast spirituality. Released in October 1966, the song became an indelible radio hit, but it was Mr. Wilson’s last moment at the vanguard of pop.

In Thrall​

“Smile,” Mr. Wilson’s next album project, which he made with another songwriting collaborator, Van Dyke Parks, was intended to be his supreme achievement. Mr. Wilson hyped it at the time as “a teenage symphony to God.”

Yet the album collapsed after more than 80 sessions in 1966 and 1967. To meet their obligations to Capitol, the Beach Boys quickly assembled two albums in late 1967 — “Smiley Smile,” a scaled-down version of Mr. Wilson’s opus, and “Wild Honey” — which had little impact.

For years thereafter, the group was adrift. The Beach Boys were caught between the new vogues of heavy rock and folk-influenced singer-songwriters, and their albums sold modestly at best. Mr. Wilson was withdrawn, spending long stretches in bed and obsessively listening to old records like the Ronettes’ “Be My Baby,” Phil Spector’s masterpiece from 1963.

Mr. Wilson’s drug use, which had begun during happier times for the band — the buoyant 1965 hit “California Girls,” he said, was written after an acid trip — had grown out of control, stunting his creativity. “I lost interest in writing songs,” Mr. Wilson once told Rolling Stone. “I lost the inspiration. I was too concerned with getting drugs to write songs.”

Some Beach Boys albums, like “Surf’s Up” (1971) and “Holland” (1973), released by the band’s new label, Reprise, still had a spark of invention.

But the band changed course after Capitol issued “Endless Summer” (1974), a compilation of the group’s early hits, which became the Beach Boys’ second No. 1 album and their first in a decade. Although the band’s live shows had long been packed with old numbers, its next studio album, “15 Big Ones” (1976) — promoted heavily as Mr. Wilson’s

Hello, my Audiolab 8200p power amp goes into self-oscillation on one channel and I'm not very familiar on how to diagnose such behavior so decided to ask here for advice.

If the misbehaving channel has 0 bias, there is no oscillation (with no load, no input signal)
if I increase bias current for more than ~10mA (~5mV on the r148/r248 resistor) it goes into self-oscillation. The scope shows it as around 3.4Mhz sinusoidal.
If there is an input signal with no bias, no load it produces a clean sinusoidal output, with resistive load on output (8ohm) it shows severe symmetric oscillation on the pos/neg peaks of sinusoidal signal no matter the bias setting.
When it oscillates I can see the oscillation everywhere in the signal path including the entry point of input diff pair.

The other channel is fine and doesn't behave like this producing clean signal.

I checked the 60v rails, and +- 12v for the opamp and they look fine. By the way I don't fully understand what the opamp does - is it a sort of servo circuit?


How would you approach such defect? Any advice?
The schematic is attached for the reference.

Thank you!

ELEKIT 2A3/300B SET AMP
Price US$1945.00 (Ll2785C amorphous core OPT)

Stereophile Reveiw : July 2023 Edition ​

https://www.stereophile.com/category/gramophone-dreams​

Stereophile Class A Components​

https://www.stereophile.com/content/recommended-components-fall-2023-edition-integrated-amplifiers




This is our first time to offer Amorphous core OPT. I want to make sure the Lundahl amorphous core is superior than the regular C Core.
This is the sample of Amorphous Core for TU-8900.. Amorphous core requires a longer burn in time..
Is it better??



No Takman for this model - Takman is running out of material to make 2% carbon resistors.

TUBE SET OPTIONS:
COSSOR/Linlai Delux 2A3 + Sylvania 12BH7A $380
COSSOR/Linlai Blackplate 300B +Sylvania 12BH7A $345
COSSOR/Linlai WE300B +Brimar 12AU7 $$695
Western Electric WE300B (5 Years Warranty) + Sylvania 12BH7A


COSSOR/LINLAI Delux metal base 2A3 $285
COSSOR/LINLAI WE2A3 $385
COSSOR/LIMLAI E-2A3 $495
Sylvania 12BH7 $95 (pair)
Brimar 6067/12AU7 $159 (pair)

If you buy TU-8900 with LL2785C and Western Electric 300B, the Cossor/Linlai Delux 2A3 is free

COUPLING CAPS 100nF 450V x 2 (VCAP CuTF $195
Cossor/Linlai WE2A3

46 x Audio Note Tantalum Resistors $5.25 each
4 x Takman 2% (3.3ohm and 8.2 ohm)
2 x AMTRANS 1% AMRG (15 ohm 2W) $9.50 each
2 x Audio Note Silver 0.1 600V $345 each
2 x Acrylic Bracket (to secure the silver caps) Free with Silver Cap









LEFT - TU-8600S (Metal Tube Cover and metal knob), RIGHT - TU-8900 (Plastic Tube Cover, plastic knob) https://www.flickr.com/photos/64593884@N08/ https://www.flickr.com/photos/64593884@ https://www.flickr.com/photos/64593884@N08/


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Matching headphone impedance/volume levels.

You can change the headphone impedance/volume levels by
simply removing the front panel and change the position of a
short pin.



Directly-heated triode tubes like the 300B and 2A3 enjoy an enduring popularity among audiophiles. The 300B with its rich midrange and extended bass- and 2A3 with its delicate expression and gentle tone offer a very special sonic experience. These 2 tubes are similar in appearance but very different in characteristics and can both be used in TU-8900 without any special changes in amplifier settings. Many manufacturers are producing 300B and 2A3 tubes so users can enjoy trying the various versions available from different vendors. *
*NOTE- TUBES ARE NOT INCLUDED WITH THE TU-8900!



■ Automatic detection of 300B and 2A3 tubes
“300B” and “2A3” tubes look similar but their respective filament voltage and operating parameters are totally different. Their supply voltages need to be adjusted depending on which of these tubes are used in the same amp. In TU-8900, the tubes that are installed are detected automatically and the correct filament voltage and voltage of B-power are automatically set. When 300B tubes are installed- the LEDs on the sides of the volume knob will light up in blue. If 2A3 tubes are installed- the volume knob LEDs will light up in green. Additionally- these LEDs on the right and left side of the volume knob will turn red when there is excessive current due to defective tubes, etc., and the current is shut down to protect the amp. The red LEDs will also diagnose the problematic tube- the right side of the volume knob turns red when excess current occurs in the right channel, and vice versa.




■ Tube-friendly design
Warm-up time for directly-heated tubes and indirectly-heated tubes are different. In most designs, directly-heated tubes warm up faster than indirectly-heated tubes- so often directly heated tubes are often overloaded. With TU-8900, the voltage is gradually raised and reduces the level of overload to the directly-heated tubes.


■ 12BH7A instead of 12AU7
TU-8900 is designed to use 12AU7 as voltage amplifying tubes. However, 12BH7A, with high driving ability, can also be used instead of 12AU7.


■ Ample space for larger coupling capacitors
Coupling capacitors can have a big effect on the sound quality. For the TU-8900, high quality conductive polymer electrolytic caps and polypropylene film caps are provided. However, exchanging for other coupling capacitors is also possible. The maximum size of the caps that can fit in the space is 22mm in diameter x 44mm in length.

■ Matching headphone impedance/volume levels
You can change the headphone impedance/volume levels by simply removing the front panel and change the position of a short pin.


■ Newly designed circuitry
The power transformer has independent windings for the right and left channel to minimize the interference between channels as much as possible. The filament power uses the latest DC-DC converter for extremely low noise and high efficiency. Schottky barrier diodes and fast recovery diodes are used as rectifying diodes that reduces even the most negligible noise spikes. Listeners can enjoy music free from noise even when using a pair of high efficiency headphones. The main circuit of the power unit is unitized per channel as a module.

■Easily change the feedback setting to NON-NFB
Many triode tube amps use negative feedback in their design. The TU-8900 has an option for listeners to hear the triode tube sound without negative feedback. In TU-8900, changing the position of a short plug on the PCB can change the setting to NON-NFB. The gain level increases by approx. 8dB when NON-NFB setting.

■ Updated more reliable tube sockets
After brainstorming with our vendor, we have come up with a more reliable 4-pin sockets for 300B/2A3. Tubes are mounted safely and securely when installed in these sockets.


■ High heat-resistant polycarbonate tube cage
The IEC (International Electrotechnical Commission) sets guidelines on thermal limits on materials and parts, such as a chassis and the tube cage. The TU-8900 tube cage top can heat up to 100 degrees C due to the heat from the output tubes. A robust polycarbonate tube cage with high heat resistance is used to meet the IEC standard.

Specifications of TU-8900

●Stock tubes 　：　300B (or 2A3) x 2pcs, 12AU7 (or 12BH7A) x 2pcs *Tubes not included
* specifications below are with the 300B+12AU7, with NFB, 8Ω loaded
●Rated output ：　8W+8W (300B) / 3.5W+3.5W (2A3) <THD 10％>
●Rated input ：　1Vrms (300B) / 650ｍVrms (2A3)
●Residual noise：　15μV (IHF-A)
●Frequency response： 7Hz-90kHz (with NFB) / 12Hz-45kHz (Without NFB)
●Input impedance ： 50kΩ
●Output impedance ： 4-6.3Ω, 8-16Ω (SW on backside)
●Input terminal ： LINE x 1
●Output terminal ： Speaker output terminals (L/R channel)：Gold-plated screw type terminal (Banana plug usable)
Headphone terminal ：6.3mm headphone jack
●Power voltage ： AC110-120V or AC220-240V 50/60Hz (3P inlet)
●Power consumption： 95W (300B) / 65W (2A3)
●Measurement　： W356xH214xD320mm (including projections)
●Weight ： Approx. 11.4kg (excluding a power cable)
●JAN code : 4952682107941

After 200 hours listening, I am confident to offer the Audio Note upgrade option:​

46 x Audio Note Tantalum Resistors $5.25 each
4 x Takman 2% (3.3ohm and 8.2 ohm)
2 x AMTRANS 1% AMRG (15 ohm 2W) $9.50 each
2 x Audio Note Silver 0.1 600V $345 each
2 x Acrylic Bracket (to secure the silver caps) Free with Silver Cap









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I just acquired an amplifier with two bad output transistors. They are no longer available. In fact, none of the suitable substitutes are available either. But I found one that seems to be pretty close. However, they differ substantially in something called the "current gain bandwidth product" which is 4Mhz on the replacement unit and 30Mhz on the original part. Everything else is pretty good. So what is this spec? And what does it mean, exactly?

This thread is intended to discuss the preparation and construction phase of building an F5 Turbo. A thread already exists for the circuit boards, so I'm guessing we will see a lot of activity here!

BURNING AMP 2025

Twenty-Twenty-Five! I can’t believe it! Another Burning Amp Fest is booked and preparations are being made, this one is going to be great!

October 4-5. Petaluma Community Center (same place as last 2 years, the space is really good for our event 🙂 )

320 N McDowell Blvd, Petaluma, CA 94954


Details to follow. Watch this thread.

Looking forward to seeing you there!!

Hi guys, i have one Soundstream MC120 with power ON and power OFF pop (bump).
It's normal for this amplifier?
I don't found MC120 schematics, maybe MC245 is similar?
Thanks in advance

I’ll go first. Which one of you guys did this?

Hi,

I have a Quad 44 which I bought a couple of years ago. It's all standard and a mark II version according to the Dada Electronics website.







I have been doing some reading regarding the Quad 44 and I am unsure about the real potential of this preamp and whether I should invest some money in it before using it, or just sell it and put the money into something else.

I am also thinking about having a passive preamp made by BTE Designs as well, so have to decide on which to do first.

Either amp would feed into a Quad 606 MK1 power amp, which I bought earlier this year and immediately sent to Quad for a service, and they also upgraded the PSU to 909 spec.

I am aware that there is the DIY route with DADA Electronics
Quad 44 MKII DIY Upgrade and Revision kit Deluxe
Quad 44 MKII DIY Upgrade and Revision kit Deluxe

I would have to get someone to do the soldering and upgrading for me due to being post stroke and my eyesight not being very good close up

Redhill Audio
QUAD 44 PREAMP UPGRADE - STAGE 1
Elna Cerafine audio-grade electrolytic capacitors
Additional, high-quality Panasonic PPS film capacitor decoupling added to remove noise from critical areas
Solid Film MKS signal path capacitors
Unnecessary signal path capacitors bypassed for reduced grain and a cleaner sound
A well chosen blend ofLME49710NA/LM4562NA National Semi & Texas Instruments Op amps for better refinement and improved detail
Quad 44 Preamp Upgrade - Stage 1

QUAD 44 PREAMP UPGRADE - STAGE 2
Increased capacity Low-ESR Power Supply Capacitors
Output signal path capacitors upgraded to solid film types
Elna Cerafine Decoupling capacitors
LME49710 & TI/National Semi Opamps
Panasonic PPS Bypass Capacitors
2 x Red Hill Audio Mini-Shunt Voltage Regulators +/-15v
Signal Path Improved with Audio Wire "Silver Signal"
http://redhillaudio.co.uk/hifi-upgr...reamp-upgrades/quad-44-preamp-upgrade-stage-2

Amplabs who do upgrades as well.
http://www.amp-labs.co.uk/q44fs-a.htm
Rob from Amplabs serviced and upgraded a Quad 303 that I bought a couple of years ago
http://www.amp-labs.co.uk/servicing.htm
He originally serviced a Yamaha CR1000 for me which I stupidly sold a couple of years ago but he only works on Quad now I think.

I have read online that the Quad 44 suffers from the 4066 CMOS Chip which was originally designed for and used in the Plessey System X Telephone exchanges, and is naturally bandwidth limited.
Other issues include the use of the Op-Amp TL071 as was used in the 405 power amp.

With the modular design and ability to have different boards the Quad 44 could be quite an asset if it sounds any good. Are the MM and MC cards any good or able to be upgraded to anything worthwhile?

Any advice, thoughts or experience much appreciated

Thanks

Lee

I've got Carver TFM-15, TFM-25 and TFM-35 amps that I use for a three way actively amplified speaker consisting of:

Altec 811B horns
Eminence Delta pro12A for midbass
Dayton Audio 12" subs

I currently use a DBX 234XS crossover which works fine except there is solid state hiss heard in the horns due to the TFM-15 not having any markings on the front panel for the input level controls nor does it have pots with detents. So there's no easy way to ensure the controls are set the same way every time the system gets used to DJ with.

I would prefer an analog crossover, but if there's a DSP crossover that is good enough for actual HI-FI use I'd be interested in that as well. The crossover also needs to be low noise as well given the Altec horns are quite efficient.

I've been on a quest to build my own own reference monitor. In that journey I've come to know the JBL m2. Maybe its highly prized for its flat response but all I see is another 2-way. There are already flat two ways on the market. So not sure what the hype would be around this speaker, beyond having accuracy and spl, making useful for far field as well as near field.
As a full-range solution if a 2 way that took care of sub bass, gets rid of another cross and thats cool. I've found a driver that could be used for the top

FaitalPRO HF146 - 1.4" Compression Driver

A woofer for the bottom can be found. The question is, how is a woofer that is going to be easily responsible from 30hz to ~1000hz going to behave? Lets say we are auditioning rap, edm, or some other deep bass reproduction that causes high woofer excursion, how is the top range of that speaker going to sound? It seems to me a 3 way is almost always better, but I'm not the finally say, the results are, anyone have a strong opinion on this?

I have been talking a little bit about this amp on the What’s On the Bench Tonight thread, but thought it’s time to give it its own proper thread. It started as a 25W Class A amp, and now has progressed to 40W - mandatory Class A operation since the topology is SE Class A with a an active push-pull CCS based on the Aksa Lender P-Chan Complementary Aleph (ALPHA Nirvana) output stage developed by Hugh Dean and used here under license to Aspen Amplifiers PLC, Melbourne. The layout is by JPS64 which means this is a state of the art amp in terms of layout symmetry, low impedance traces, thousands of sticking vias, and careful attention to minimizing ground loops and noise immunity.

Some of the notable features that this amp will have includes:

• Dual Monoblock design with independent power transformers and amp boards
• Solid State Relays (SSR) for speaker DC protection similar to the RTR SSR designed by jhofland
• SSR Soft Start with soft mains On/Standby button in front panel similar to the SFP designed by jhofland
• Custom All-CNC milled and satin bead blasted hard anodized aluminum chassis with thick 5mm walls and massive 40mm heatsink plates. The chassis is a massive amount of aluminum on the order of 25 to 27lbs. Chassis look, shape, HMI and layout is all my own design and the 3D modeling and CAD is by Darko M.
• Dual analog meters for output power with backlight
• Premium Viborg copper binding posts
• Premium gold plated RCA jacks
• Front panel Mute switch via SSR enable
• Automatic over temperature safety shutdown with dual thermostatic switches that activate the SSR
• Maximum output power of 40W into 8ohms and the wonderful ALPHA Nirvana 2nd harmonic dominant distortion profile with relatively low THD of circa 0.005% THD at 2.83Vrms into 8ohms
• Beautiful classic lines for an enduring timeless visual look

This will be offered through my XSA Labs website and we plan to offer a limited run of 25 first production units at an introductory price of $1599.




We are exploring anodizing color options for the handles and heatsinks. All black is still a major contender.



The internals will be laid out like this with the amp and its PSU mounted together on each heatsink. The floor of the amp will house the dual toroidal power trafos and also a main board let’s the SSR’s for the soft start, the main IEC soft On/Standby, and speaker SSR’s.


Here is a closeup of one channel of the amp and on-board CRC PSU on one PCB assembly. You can see the temperature sensor on the heatsink. Keantoken helped with the construction and assembly of the amp PCBA.


Initial testing of this amp indicates it sounds superb and the latest work is expand the chassis an extra 50mm deep to reduce heatsink temperatures and permit full 50W operation.

You can listen to it here:

Vanguard speakers
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XSD speakers
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As the beloved SSLV1.1 BiB shunt reg was getting long in the tooth, especially for NOS JFETS, I had in mind for some time now to design its successor. The goals were: 1. In production parts 2. Much simpler to set up. 3. Better technical and subjective performance.

After many breadboard experiments and two prototype PCB iterations I feel that my goals were finally met. So here comes the UltraBiB V1.3 😀

-Uses no NOS parts.
-Can do 5V to 40V output without changing a thing in its parts configuration.
-Nothing to choose and match. No tolerances in predicting its CCS limit setting.
-Has 45dB more open loop gain and many times less output impedance than 1.1
-Sounds easily better.
-Its an electrically and mechanically drop in replacement for an upgrade from 1.1

I have already given spare earlier proto boards with now deleted experimental features to few local beta testers. They are all happy by now as far as I know. The pictured board in green is the final layout in just cheapo proto that's a pain to rework and its pads vaporize in the end. It will come in proper grade black solder mask and immersion gold three sections board just like the original.

Attached: Zout plot for 150ma spare current and noise plots for 100,150,220,330,470,1000uF C2 (red 220uF). Also the rails probed on the scope for positive and negative sections. Here are typical values schematics also. I will write a PDF with instructions. Not that there is something truly special to consider when building it with the suggested parts but to describe it better as an item and to clarify details and precautions.

Updates:
31/5/18 R9's value update
1/6/18 OL sim at 100mA spare
2/6/18 Build Guide PDF added (0V0b)
24/5/19 Triplet board dimensions picture
21/6/19 The PF5102 JFET became EOL. But GB long term supply is secure. For substituting with J113 see info in post #1559
15/5/20 BC560C became EOL. But Group Buy long term supply is secure. BC559 can be used up to 30V output. BC556 for 31V-45V output.
2/7/23 LNA instrumentation measured a very low 2nVrtHz spectral noise density from the UltraBiB under real working conditions. post#3,688

3 sets of PCB for Parallel LM3886 EC/Comp Amp. THD+N<0.0006%, Noise10uV. (see my post and measurements)

4 layers 1 OZ, 1u Gold ENIG

25USD per set ( include two PCBs, schematics, a simple build instruction, BOM) plus post 10USD for US and Canada, 15USD for Europa.

Please PM

We'll be improving the enhanced thread print function (a donation only feature) in the future.

To be sure we create a tool that does exactly what it needs to, we'd like to know how YOU use this feature currently.

Do you actually print?
Do you save it for reference and look at the file offline later?
What's important to be in there, and what's important to not be in there (eg: text or flourish that serves no information purpose but would consume ink if printed)?
Options for turning images on or off?

Right now we're not sure what's important to you. Please let us know 🙂

Hey DIYAudio community,

I'm excited to introduce Valvalyzer—a dream come true for anyone passionate about vacuum tube circuit simulation. If you’ve been searching for a tool that lets you dive deep into tube circuit behavior without the complexities or limitations of SPICE, look no further.

Valvalyzer brings together classic tube-era theory and cutting-edge computation in one free, interactive package. It lets you visualize, tweak, and understand every nuance of your circuits and transformer designs with precision and real-time feedback. Whether you’re a seasoned veteran or just starting out on your DIYAudio journey, Valvalyzer is designed to empower you to innovate, experiment, and truly make your mark.

Check it out, download it, and let’s revolutionize tube circuit simulation together. I’d love to hear your thoughts and see what you create!

— Jim Reese, AmpCad.com

Hey,
Planning on building the Paul Carmodys The Pit Vipers.
Built a couple of amps and pre-amps with a lot of help from this amazing forum.

Recently got a workshop in my possession so I think its time to make a couple of speakers now when I have the space.
The plan is to make something quite simple and I found the Pit Vipers which seem pretty straight forward.

I do have a few questions though. (probably stupid)
1. What is the best kind of material for this kind of speaker? MDF?
2. The plan that Paul Carmody doesnt specify the thickness of the material. Can I just assume the thicker is better? Thickness would change the volume but not to any large extent.
3. He is using a 6" PVC end cap on the midrange. Wouldn't be better to make a proper enclosure?
4. How much damping should be done? All sides, top/bottom?

Hiya,
Been posting some pictures here and there of a new project I have started on, might as well share the whole thing. The idea started in 2018 for a regular amp (speakers), but life happened and I lost track of audio once more. The good thing is that I already have some parts that I can re-use, so in today's thinking "they are free".

Goal:

• Headphone amplifier, 35 ohms
• Tube, single-ended,1000-1500mW of raw power power
• Daily beater, so no rare tubes, nothing end-game, just good music and a cool looking piece of kit
• Must fit on desk and desk must not collapse

Tubes:

• 4P1L
• 2P29L or 6E6P, might also look at other wee tubes like 6Z49, 6C4S, 5842 etc

As I want to tinker with the driver tube a bit, the power supplies will be setup to be universal for a 250V output tube and a 200V driver, current for each tube can be up to 50mA with headroom left.

4P1L will run at 225V/30mA/-19V initially (245V/30mA B+)
6E6P will run at 200V/30mA/-3.4V, 2P29L will be 6mA/-20V, so we have 30mA/-20V as worst cases for the PSU (225V/30mA B+)

As I am betting on the 2P29L, the rest of the info will focus on this combination so as not to have two projects in one.

Supply Chassis:

• Separate chassis for raw DC supplies to conform to the "must fit on desk" rule
• PCBs
• B+ will be SiC diodes, eChoke and MKP caps
• Filaments with SiC diodes and FW/KW caps

Signal Chassis:

• Filter for DH filaments, then Coleman regulator (current source) for DHTs
• LDO voltage regulator for IHT
• Passive B+ filter with RCRC to tune for both stages

Iron:

• 2x SE OPT 10K/50mA
• 2x Lundahl LL2763AM-40mA interstage
• 2x Toroid 250-210-0-210-250V/330mA, 12V/4A, 12V/4A

signal path



eTracer loadline on one of the 4P1L I have tested. 1.2W max with 10K.



Step 1: Concept
Step 2: Design PCBs for test setup
Step 3: Test
Step 4: Build chassis and integrated PCBs

Hi,

I am looking to build a volume velocity source for measuring acoustic and vibro-acoustic transfer functions. The design will use a ~15ft 2" ID hose with a nozzle that has a microphone mounted to it to measure the source strength. The tube diameter is to act as an omnidirectional point source up to 2-3 kHz and the reason for the length is to decrease the length mode resonance so it is lower in frequency and the peaks are spaced more closely.

My question is what sort of driver should I use to drive this to high sound levels from 100Hz to 3kHz? My initial thought was to use a compression driver as that is what several commercially available volume velocity sources use. The issue with this seems to be getting something that will drive high levels below 200-300Hz. However the celestion Axi2050 seems promising. Are there better options for compression drivers that could do this or maybe less expensive options? Or maybe I would get higher levels or better results from something other than a compression driver?

I'm not very concerned with distortion levels or linearity as I will only be looking at output/input transfer functions so all of that will be accounted for. I am mostly looking to be able to drive the highest levels I can.

I'd love to hear people's thoughts on this one.

Also I wasn't sure on the right sub-forum for this so feel free to move it if I have picked the wrong one.

In theory and in practice, if you put multiple drivers together as in a line array, you are increasing the surface area of the cones. That in itself should be enough to push more air as if one were using a singe larger driver. However, according to one speaker designg program, this configuration does not afford any lower frequencies as if it was a single large driver.
So, could some one tell me why this would be so?
Thanks in advance.

I am looking at winding my own inductors. I am trying to figure out how to do it without too much headache. I have access to 3d printer that can print a variety materials. I want to make fairly large 2.0mH 15A coils. Any tips? I can get fairly long 16AWG PTFE insulated silver coated copper wire scraps from local electricians I work with.

Is there any procedures available without having to redesign the wheel? I have a mini lathe. I am told to go with P-core if I can find a bobbin big enough.

I'll never need to drive more than 200W into the load. These are for PA speakers which I use at parties and outdoor electronic drum kits and synths.

Ultimately, i'd like to make something like the photo attached but better.

Thanks!