Something to lighten the mood

So I kick off early today like many are doing during this C19 crisis and I thought I'd do a little housework before the Mrs. came home. I started making the bed and I noticed a pillow was missing. I look around and see it on the floor at the end of the bed. Only problem was, it was moving. It seems that little Bingo was playing hide and seek with Daddy and had now trapped himself inside. Lifted him onto the bed, freed my little prisoner and went onto finish my work. It was funny enough that I thought I'd share because I think we can all use a little something to help us smile these days.


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Some speaker driver measurements...

Dear friends,
there are many enthusiasts of loudspeakers building here so I thought this link would be very useful for someone.

It is needed to register at the website to have an access to the speaker drivers compare feature.
With no registration one can click on driver model name in the table and get to the speaker driver measurements page.
There is the mesurements description above the table. Just click on it.

To moderator - sorry if I place this thread in a wrong place, you can transfer it in the correct place.

Best regards,

5.1 Massive Surround Planar Headphones

Hello! I am new to this website so lets see how things go! Over the last two years ive dedicated almost all of my time to the creation and experimentation of membrane based speakers like planars and ribbons. And I like to post about some weird experiments from time to time, this is one of them. Some months ago I custom made a multi speaker headphones with two custom 90 x 45mm planar drivers per side like an open book.

The point was to try make a larger "ring" of sound around your head, hence why they had no pads, since your ears are meant to be "immersed in sound" and pads would push your ears away from the speakers. This ended up being fairly successful? Although not enough to make it worthwhile over a normal, single larger driver. However, when i posted about it on reddit, people gave me an idea. What if i connect each separate speaker in surround through a 5.1 speaker amplifier to improve imaging directionality? So i did, which was clearly a nightmare..


The experiment was slightly successful, it had slightly better imaging, but not too noticeably. So Ive thought about it and decided the issue was the MASSIVE speakers this thing uses. They were so big that even when i just played the front speakers, i couldn't tell very easily from listening that the speaker was placed in front of my ear which is important when im trying to make it easier to tell what direction sounds are coming from through surround, however they were not designed to do this.. So i decided to start working on a pair that were designed with this in mind. So ive been developing a 3 speaker headphone using much thinner ribbon drivers again, custom made by me for better directionality, using 7.1 surround this time. (Thank god i made sure to buy a 7.1 amp) I will be sure to make a post once they're done, but i hope atleast some of you enjoyed this weird experiment. Also, in case any of you were curious what happened to this iteration of the idea, the magnets snapped through the housing a month ago, breaking one of the diaphragms, so yeah even more motivation to finish a V2 :)

Op Amp blind test: Burson, ADA4627, NE5534

Earlier this month, Mr. @John Burson sent me a private message and asked if I would be interested in reviewing his discrete op amps in my freshly build AD1862 DAC. Of course I would. He was kind enough to promptly send me two V6 Vivid op amps in exchange for photos and review. Thanks John!

Here’s the first part of my write-up.

My background

I have spent a number of years building up projects in hifi and guitar amplification contexts, and while I have a basic level of electronics literacy, I have not yet developed a circuit for myself and thus consider myself a diy builder, not designer. I am a simple hobbyist.

In general here are some of the biases I bring into a comparison (whether these biases are true are false is perhaps a different topic. I realize that they are my biases):

  • Circuit design matters more than the grade of individual parts
  • Power supply matters more than the grade of individual parts
  • People that spend lots of time swapping op amps, tubes, and capacitors should sometimes just build or buy a different piece of gear
  • I generally do not believe in burn-in in active devices and am not interested in expensive cabling.
I have run loads of tubes for over a decade. I do think that old RCA’s / GE / Mullard sound better than new JJ’s. But after owning them all, I just run new JJ’s and make circuit adjustments. At this point in my life, that’s the kind of person I am.

I am also running an NOS R2R DAC and a Pass F5 amplifier so clearly I am not immune to audiophile appeal and perhaps desirable distortion.

Op amps are interesting parts in the sense that they are monolithic devices which contain quite a bit of circuitry. Really you could run a simple and great sounding preamp with 1 dual op and a simple power supply. Do I believe that changing preamps would make my system sound different? Of course. So, it stands to reason that changing 2 op amp stages per channel would similarly make a recognizable difference.


I am pulling in a good friend (Friend #1) who designs audio gear at a well-regarded major manufacturer to listen to op amps with me. I am also trying to convince my friend to run some basic tests on a pile of op amps to give us data regarding what we are hearing.

I will be testing ADA4627-1 (currently in my DAC) VS NE5534 VS Burson V6 Vivid (and possibly also possibly LM741 and TL071 if these two are stable in this circuit).

On an upcoming weekend, my audio design friend will swap op amps for me while I listen in a blind test with a second friend. Friend #2 has almost 0 exposure to audio comparisons but is a foody and generally detail oriented, so I am particularly interested in his impressions as he does not have a horse in the race.

The only op amp I will listen to before this blind test will be the ADA4627-1’s which are currently in my DAC.


My hypothesis before blind testing:

I expect to be able to consistently identify op amps 1, 2, and 3. Going into the test, I do not expect to have a strong preference for any of the 3 op amps over any of the others, although I do expect to have favorable opinions of all. I expect that the Bursons will have the largest subjective soundstage because of their slightly increased harmonic distortion profile (discussed below). Finally, although the NE5534 is old and inexpensive, I expect that in a blind test it will be rated as a peer to the other two options.

Friend #1 (engineer) hypothesis:

“I think [all] sets of op amps will sound good as the circuit around them is good. That being said, discrete op amp will show more nonlinearities and harmonic distortion. Whether this is desirable or not is up to the ears of the listener”

And when questioned about harmonic distortion:

“I like it a lot in the recording process. But for playback, I think that being faster and more accurate to better hear what the engineers did is more important.”

Friend #2 (new to audio) hypothesis:

[will add shortly]

Harmonic Distortion

User @Martigane tested Burson op amps in his Whammy in 2020 and provided some useful measurements. In particular, check out the harmonic distortion profile of the Burson V6 Vivid:

burson v6 harmonic distortion.png

This looks similar to the distortions in many of Nelson Pass’s JFET circuits. I am assuming that most people on this forum are familiar with his amplifiers. In particular the SIT amplifiers and the H2 buffers feature 2nd and 3rd order harmonics as a major feature in the sound of the amplifier. I ran tube amplifiers in my home for a long time, including a JE Labs 2a3 stage, and felt that they often threw huge sound stages. Perhaps the Bursons will nudge my rig in that direction.


Next posts will feature close up photos and more details. I am currently running a Miro AD1862 DAC into an F5 amplifier, with no preamp. In this context, the op amps are overwhelmingly the largest active parts count in my setup.

Germanium Transistors! Help!

I need help with the datasheet of NTE102A and NTE103A. Attached is the datasheet.

Everything looks fine, except one thing : the datasheet says :


" NTE102A (PNP) & NTE103A (NPN)
Germanium Complementary Transistors
Medium Power Amplifier "


" Common-Emitter Cutoff Frequency, fαe, at VCB = 2V and IE = 10mA : 10KHz "


Also :

I am extremely interested in Germanium transistors. I have found AD161 and AD162 at AliExpress, but, these are 20V.

1. I would take any NPN and PNP, even, when they are not complementary ( yet, kind of, similar, to some extent ).

2. Ideally, all voltages best be >= 40V. In case this is not possible, they must be >= 30V.

3. The current best be >= 100mA. Lower currents may be OK, such as 10mA or, even, 1mA.

4. They best be audio rated, yet, I would take anything.

5. Soviet or Russian OK.

6. Please, be kind to provide numbers. Websites are very difficult to search.

I have found some sites, again, all except NTE are difficult to search :

Germanium Transistors - Page 1 - Small Bear Electronics

Parametric Search | GP BJT | New Jersey Semiconductor

Transistors | Germanium Transistors | NTE Electronics

Comset Semiconductors - Welcome


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DIY ACA mini

The DIY ACA mini (Amp Camp Amp mini) is in the process of shipping to
the Burning Amp Festival lottery winners and a few of the helpers and

I am pleased to present the DIY ACA mini article here (in two parts as it
exceeds the size limit of the forum).

There has been at least one addition to the design since BAF, and here's
your chance to look at it again and in more detail.

I am hoping that 6L6 will provide us with one of his usual exemplary build
guides, and I anticipate more general availability of this piece in the
future, as it was intended as a low cost, easily accessed project.



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Suggestions for 50W Mono Class D PCB which can drive 4-16 Ohm speakers


I'm interested in a Mono Class D amplifier PCB or populated PCB which can drive 4-16 Ohms speakers to approx. 50W with reasonable THD. This is for an instrument amplifier, so THD up to 0.1% (max.) would be acceptable and a frequency range 60Hz-18kHz would be transparent enough for the application.

I see some very cheap PCBs on eBay/AliExpress and more expensive PCB from various other companies.

But this needs to be reliable, I want something that last and won't blow-up! Any suggestions?

Designing my own is an option and would be fun, but I'm much rather use something that is already well designed and tested; why re-invent the wheel.

Open Baffle Speakers DONE!

OH MY!!!! Just finished the open baffle speakers. Hooked them up to my main system. Turned it on and nearly fell over on the floor.....Holy Schiit! do they sound great! Using the B&W ASW608 subwoofer.....The spacialness is amazing, even without a hard wall behind them. My living room is very heavily damped so the bit of extended highs that the Tang Band speakers exhibit is very welcomed......These speakers have a total cost of $225 for the pair.....The plywood is extremely nice bamboo plywood from Lowes ($21 for 2' X 4' X 1/2", Drivers are $79 each, misc connectors etc rounds it out.......OK, they are not Magnapan MMGs or KEF LS50 Metas...But they absolutly bury and of my under $1000 speakers....As long as you use a subwoofer. As you can imagine bass rolls off fast around 100Hz.....I'll do some measuring next week and report.


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DIY Open Baffle Info Needed

I like building HiFi speakers. Recently I became enthralled with the concept of open baffle. Where can I find concise information on what specifications I should be looking for with regards to a 10" or 12" full range or coaxial driver? Any recommendations for drivers around $150 each? Are there any online DIY plans or websites I should be looking at? Thanks in advance!

Hafler DH-200/220 Mods

As suggested in "hafler dh-220" thread to repair it, here is the starting point of mods that peoples have done on this amplifier.

So far in previous abovementioned thread, 2 mods were brought up:
#1) Replacing the load resistors in input stage with current mirror. I believe that this mod would increase the open-loop gain of the amp, thus would increase the amount of feedback. Is it good or bad? or can we re-adjust the gain of the input stage or play with the gain of the driver stage so the overall open loop gain is not modified?
#2) Regulating the power supply of the circuit (except the mosfet output stage!). This one I have personnaly done. See attached principle. The regulated voltage can be higher than indicated on the schematic so the maximum power loss is not much. Has someone else tried this mod #2 also? Even my girlfriend (who are not an audiophile) noticed the improvement on the sound (she was not trying to be kind with me...).

Note: the modifications I have suggested here on my part in this whole thread should be done and integrated only on a new pcb layout for final use. My goal here was to test the mods as prototypes only for evaluation purpose. I do not recommend someone else to do it the same way as shown.

My stuff USSA, FSSA:


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Aleph J illustrated build guide

An illustrated guide to building the Aleph J

This is a guide to building the Nelson Pass / Firstwatt 'Aleph J' amplifier.

A few links to start off -

Aleph J Manual (From

Amplifier PCB (From DIYaudio) Aleph J (2 PCBs included, which makes 2 channels) - Circuit Boards

Discussion thread - Aleph J for Universal Mounting Spec - diyAudio

Bill of Materials (BOM) - diyAudio

Schematic -



The bulk of this guide is going to show the green PCB, which were proof-of-concept prototypes. The boards worked great and we needed to make very minor changes to the production boards, which are blue. There is effectively no difference between the prototype and production boards. Also worth note, the photos of the PCB will be from two different builds, mine (6L6), and Grimberg's. There are no significant differences in how the PCB was stuffed or utilized. I think Grimberg did a prettier job stuffing the PCB than I did. :)

Also, this build will show a 5U 'Big Amp Chassis' from the DIYaudio store. (Because that's what I have on hand.) The Aleph J can be made into the 4U 'Jack of all Chassis', everything will fit and the heatsinks are (just) big enough. All the specifics surrounding the 'premium' chassis (back panel, perforated base, pre-drilled heatsink, etc…) are functionally identical, the differences between the 4U and 5U are mainly just size. Regardless of the chassis you use, this amp does get quite hot, and good ventilation will be required around the entire chassis.

On to the guide.

Here is the PCB. It's a great layout, please thank member Didiet78 for his work making this. :D





Stuffing the PCB

The normal order of operations is to do the little things first and place the bigger things as you proceed.


This PCB has 4 connections that are normally going to be jumpers. (R6, R30, J1, J2) You can see them here. These connections can be jumpered with little bits of wire or cut-off resistor leads, your choice.
These 4 pads are there in case you need to add some resistors in case of oscillation, which may happen to some builds. It's rare, but if you need it, there is place on the PCB to add some compensating devices.



Let's talk about this - as it is somewhat confusing.

There are 3 places for R27 on this PCB. The first is the pad next to the cap C2. (in the above photo it is empty) I suggest making that one a jumper.
Where the jumper is placed in the photo should be open, and under the green insulation you will find the place for a pot.
SO - place a 100K pot where the pot will fit and jumper the vertical 'R27'. Set the pot to 68K before you turn the amp on the first time.


Here you can see how the pads for the pot are arranged - (underneath where it says "LTP Bias" and similarly under "offset")
The small oval pads are where the pot connects. The larger round pads outboard of the silkscreen are for a resistor if you choose to put it there in lieu of the pot, or can be used to measure across the pot in circuit. Cool, huh?

Also, it does not matter which of the center pads you use - some pots have all three pins in a row, some have the center pin offset. Either type will be fine.


Add the resistors. Shown here are big-bodied Dale RN60. If these fit, and they do, most other resistors will as well. Use whatever parts suit your fancy.



Now add the bigger (3Watt) resistors. It's a good idea to leave some room between the PCB and the body to let air circulate. As shown here -



The best advice I can give you is this - measure every resistor before inserting into the board.


Continue on with caps and the small transistors



Eventually the board will look something like this -


For reference, know that the Power Mosfets (obviously not mounted yet…) on the Left side of the PCB, near the electrolytic capacitors are for the Constant Current Source, and the Mosfets on the Right side, closer to the red input film capacitor, are the Outputs.


Note that in this photo, the vertical R27 is jumpered, and there is a 68K resistor in the horizontal spot. I later replaced the resistor with a pot.


Here is the pot in that position. I used a single-turn because I had one on hand... I strongly suggest multi-turn pots on all of these projects.

Yes, have my LED colors reversed. The V+ should be red. I've even had it marked backwards in the schematic. Lol. :) You could make them all blue, this is a Pass amp, after all… :)

The LED on the PCB are there to show that you have the rails connected and the amp PCB is getting voltage. If you want to extend the leads on one of these and make it a panel light, feel free.



Power Supply

The power supply for the Aleph J is going to follow the basic pattern of the Pass/Firstwatt DIY amplifiers. Please look at the following schematic --


The basic topology is this. 18+18V transformer, of at least 300VA, CRC filter with 8 15,000uF 25V capacitors and 8 (4 per rail) 0.47ohm 3W resistors.

May you use a transformer with more VA? Yes, of course.
May you use larger Capacitors? (more uF) Yes.
May you use capacitors with a different voltage rating? Yes, as long as you have 25V or more. (25V, 50V, etc…)

Remember that the factory Firstwatt amps use 300VA transformers and (8) 15,000uF 25V caps. If that's good enough for Papa… It should be good enough for you. But almost everybody makes it bigger. No problem at all. It's easy, so you might as well... :)

In this build I am using the old (smaller) DIYaudio PSU board. This particular one has no blue soldermask on the top of the PCB. It is otherwise identical. The section for the discrete diode bridges has been snapped off.


IMG_0822 - My Photo Gallery
Here shown with the Filter resistors (0.47Ohm, 3W, light blue), the Bleeder (2.2Kohm, 3W, dark blue) and LEDs.

For some reason I can get the LED color correct on this PCB… Red for V+, Green for V-

The PCB can accept (8) caps with 10mm lead spacing and 30mm diameter, or (4) of 35mm diameter. These are 33,000uF 35V Panasonic T-UP series caps.


I prefer to use diode bridges in these monolithic blocks.


Bridge connections.



IEC inlet.


120V AC wiring shown - this is the primaries of the transformer. AC will attach to the center terminals.

You are free to comment or question. :D

The Black Hole......

This new thread is intended to supplant the recently closed Blowtorch thread which the Moderation Team had felt had run its natural course.

This new thread will be moderated very differently and will be subject to the normal diyAudio rules:


with which we would ask all those who intend to post here familiarise themselves.

In addition to the above rules this thread will also be proactively moderated meaning that posts and consequent replies that we feel are going to veer off course or that may lead to personal insults will be deleted.

If the message doesn't get through then those continuing with such postings will find penalties are swiftly handed out. For some of you even a 1 point infraction will automatically place you in read only mode. All those effected by that have already been informed.

What we would like to see here is thought provoking and interesting discussion of anything technical that is related to audio (and other spheres) but we do not want rehashing of material that has been flogged to death in other areas of the forum including the now closed BT thread.

Enjoy, have fun and keep to the rules...

bypass capacitor in a speaker, same type?

Hi Everyone,

I'm hoping some one with empirical experience can help me. I have clarity caps in my tweeter crossovers and wonder what you've tried. Pure theoreticians need not feel obligated to contribute. :)

I know many try to roll together more expensive sounding caps by mixing medium quality with small bypass high quality caps.

I'm wondering if anyone has tried bypassing caps with the same kind? For instance, a Janztzen superior 4uF with a Jantzen Superior 0.1uF or the likes. Is it worthwhile, or is it more worthwhile when mixing up caps?

I was thinkng of bypassing the Clarity's with other clarity's, but their bypass caps are expensive, like $30 for 0.1uF. I'm trying out Audyn True Coppers right now, at about half the cost of the CC's. Still about 5 days short of their break-in period.



3D printing enclosures without actual knowledge

I hope me asking a question on how to avoid gaining audio knowledge is not too un-fanatic, and it is not meant to belittle your (frighteningly complex) hobby.

I like 3D printing.
And I would like to play around with different (smallish, because of build volume restrictions) enclosure designs until I find the nicest one for my home.
And I would like to do this without getting into yet another hobby, if at all possible ( ... at least I can try). So I would like to bypass all the knowledge-intensive parts (measuring a driver, simulating it with different volumes and designs, evaluating response curves and deciding which one corresponds to ´nice´sound ..... ), if at all possible.

So my question is :

Can an audio-fanatic distill its knowledge into a set of parameters that sufficiently describe an enclosure so that it will at least sound ´okay´?

I hope that something like the following is possible:

- Take well-known driver a
- Put it in a volume x
- Put in a port of area y and length z
- make sure that no two walls are more than l cm apart and/or parallel to each other
-> And whatever you do, you will get ´good enough´ sound down to soandso Hz.

This would allow me to happily try out shapes without fearing that it is utter nonsense from the beginning.

Would this be possible - or is enclosure design far too complex to be distilled down to a finite set of parameters like in my example ? And if yes, which parameters would be neccessary?

Thanks for your time !

Is it possible to cover the whole spectrum, high spl, low distortion with a 2-way?

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?

UNSET Beta Board Build

This is a new thread to detail the building of the UNSET Beta Board, and its use in building an UNSET amp. This thread should only be used for discussing the board build, and all other UNSET questions and discussion should go into the existing UNSET thread here:

UNSET is coming?

These first few posts will contain the build documentation as it exists today. It will continuously be updated with the latest build documents. Some of these are a bit thin on info, but I need to put it up so that some can start their builds. So far only 8 people have boards. I'm sure that new issues will arise, and they will be addressed here.

There are two schematics. The Eagle schematic was used to generate the board files. It is somewhat confusing with two sets of mosfets and all the jumper pads, but it is an exact match for the board.

The Simplified schematic has all the unnecessary stuff removed, thus it is a bit easier to follow.

The preliminary Bill Of Material (BOM) is here. All of the part listed are the same as what's in my board which has been tested to 660 volts.

I have added an Excel version of the BOM. I had to zip it so it would upload since .xls is not supported.


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Keantoken's Aurum-X 300w Amp with LatFETs

This thread is for the technical discussion of Keantoken's lateral FET 300w Class AB amp inspired by the amp in this thread. Aurum is Latin for gold and X refers to the 10 years where this amp design has languished silently, waiting to be resurrected from the ashes like the phoenix it deserves to be. The goal to develop what was touted by certain forum members to be "the best amp they have ever heard" into something more modern, using readily available components, and using state of the art layouts. Keantoken, JPS64 and myself will work to develop this into a relatively easy to build amp that can be used for projects requiring a little more oomph than usual. I currently don't have a 300w amp on hand so I thought why not go with one? I got Keantoken and JPS64 together, and away we go!

Here are the relevent design specs/requirements:

Power: 300Wpc into 8ohm (minimum Rser>5.5ohm). For 4ohm loads will require more design work, TBD.

Gain: 31.3x or 29.9db

Sensitivity 4.426Vpp or 1.56Vrms

BW: DC to ~2MHz at -3db.

Slew rate: 135V/uS

THD at 1k simulation: 0.0013% at 1KHz full power, 0.0002% at 15W. note that layout and other factors can easily add 0.0005%

We will need +/-70v rails and secondary set of rails at +/-80v for the input stage. The way to do this is still under development but an option being looked at is a custom flyback transformer/regulator.

We will be using Exicon ECX10N20 and ECX10P20 MOSFETs and they will require either Keratherm or ceramic insulator pads with thermal paste for maximum heat transfer. We need 0.1 deg C/W heatsinks to run full power.

Here is the current schematic:

Predicted FFT for 15w into 8ohms:

Draft placement of components so far (note optional Molex Minifit quick connects for flying leads for the outputs):

I want to thank Keantoken and JPS64 for their contributions to realize this amp. You guys are fantastic to work with! Hopefully we are not too far from a working proto. :cheers:

Edit Apr. 28, 2020 - Prototype Ready Manufacturing Schematics and Renders here:
Keantoken's Aurum-X 300w Amp with LatFETs

LTspice schematic for Rev 1.0:

Render of Front End board:

Render of Main Board (note that there is a built in solid state relay (SSR) for speaker DC protection):

PSU Topology:


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Quad 44 occasional sharp crack!

Hi All!

My late 44 (s/n 034981) is hooked up through a 405.2 to a pair of cheap 4 Ohm speakers and I am having difficulty replicating the occasional sharp crack that I was getting more regularly through my Spendor LS3/5a speakers.

The 44 was last serviced by Quad in 1995. I carried out the 'Erratic input switching' mod and mistakenly used a 47uf cap instead of a 4.7uf cap. Later after use it stopped completely, and it is now working again after replacing the relay and blown zeners 404/5 and the 47uf switching mod cap.

I have been using the 405.2 regularly with a 33 and have had no trouble with it.

2 hours and not a crack in sight. Does any one have any idea what it may be. I want to sell them but don't have the confidence while I have this issue.

Many thanks
Enthusiastic and an amatuer

Aleph 30 weak bass

Hi, I have an Aleph 30 from about 2004 that exhibits weak and distorted bass; midrange and treble seem fine. I've measured the rail voltages, bias currents and output offsets and all seem fine. Although physically, everything looks fine, I'm suspecting the 16+ year old power supply caps. Does that seem reasonable, or is there something else I should be taking a closer look at?

new SiC JFETs ?

March 14, 2014 - United Silicon Carbide Inc. releases Best In Class 1200V SiC JFET Transistor
United Silicon Carbide Inc. (USCi), releases its portfolio of 1200V Silicon Carbide JFET product in die form and TO247 packages. The breakthrough United Silicon Carbide xJ series of 1200V JFET's are the industry's lowest RDS(on) SiC transistor device. This market milestone for silicon carbide enables best in class converter and inverter system efficiency through incorporating the lowest figure of merit ( FOM) switch commercially available. The depletion mode xJ JFET series takes advantage of silicon carbide's significantly superior performance over silicon, offering the user the best wide bandgap switch at standard 175°C Tj max. When appropriately packaged, the xJ series is capable of operating at temperatures of 250°C and beyond.

Designed to achieve best in class system efficiency, improved thermal characteristics and industry leading FOM – the xJ series enable the most efficient switching solutions for both power discrete and power module applications.

United Silicon Carbide - USCi News

and also: CoolSiC? 1200V SiC JFET & Direct Drive Technology - Infineon Technologies

  • Poll
What is the Universe expanding into..

Do you think there was anything before the big bang?

  • I don't think there was anything before the Big Bang

    Votes: 42 12.2%
  • I think something existed before the Big Bang

    Votes: 141 41.1%
  • I don't think the big bang happened

    Votes: 41 12.0%
  • I think the universe is part of a mutiverse

    Votes: 161 46.9%

Just for interest,

What is the Universe Expanding Into?


A poll has been set and it is multiple choice the poll is on going...please read the thread before voting..

M. Gregg

The making of: The Two Towers (a 25 driver Full Range line array)

After riding along on a few different line array threads I figured this project deserved it's own thread.
I wanted to get new speakers for my living room for a while but could not quite find something I liked.
The speakers I have right now are just too big to use in a proper setup. In a domestic setting with a girlfriend and a 7 year old son there's just not much room to place anything. After surfing the net in search for an answer I stumbled over several line array's.
Now that was something I thought had potential! Way lower floor space needed than my current speakers with 15" woofers.

So the idea was born to build line array's using 25 full range drivers in each array, long enough to somewhat be floor to ceiling.

Next problem, what should it look like? And what materials to use? I remember seeing a DIY thread with a translam construction. That idea was very appealing to me. You can make it any shape you want on the outside and the inner walls can be used to benefit the design.

I started up my favorite 3D program and started sketching. Pretty soon I had some ideas about the outer and inner shape. Here's a much later version to give an idea:

I wanted a round outer shape, round corners to help reduce diffraction. On the inside I choose a wavy shape to hopefully aid in scattering/diffusing the back wave and making the walls uneven in thickness. That last feature should help reduce resonances of the enclosure.

Also obvious are the braces, making it a potentially very stiff enclosure.

The total array design on the left and the final outcome of this project on the right:

(not too far off I presume)

Here's a list of (hopefully) useful shortcuts to different milestones and/or projects done with the arrays:

A memorable moment, first sound!
It took a long time to get there, was it really worth it?

13th December 2014, First sound: A memorable moment!

Measurements begin...
My journey to better sound

14th January 2015, Start of first measurements: Measuring my way to better sound quality

Break trough in processing...
stepping outside of the boundaries of DRC-FIR

16th July 2015, Break trough in processing: Getting time coherency to work
(creating a time coherent correction in my listening room)

Proof of time coherency, at last :)

12th January 2016, Proof of time coherency at last! Tested with APL_TDA software


Adding Ambience!
Taking control over the room

With installing a virtual Haas Kicker I'm trying to restore some of the energy I "robbed" from the room with my damping panels. I had some clues it might be interesting from my Car Audio days and always wanted to try a proper version in my home. By far one of the most fun tests I have done!
It starts somewhere here... with a later revisit of the theme here! The second part is concentrating on adding reverb to the ambient channels. I can highly recommend playing with this Haas Kicker idea, be it virtual or trough diffusive panels.

Review time!
Printed as is, I hope more will follow

21st January 2016, First official review: Jan Fekkes reviews the Towers

Shuffling the phase, how does that work?
Another interesting, hopefully successful experiment

A thread was started on Fixing the Stereo Phantom Center which inspired me to do some tests with it. Early on it made me do some mid-side EQ, following a paper in that thread. Later on it led to experimenting with a phase only shuffler to brighten up the phantom center. What I think is happening can be read here...

Condensed version of this thread?
For those looking for a more condensed version of this thread, I started a post (a couple actually) on the JRiver forums that's more compact, but it also lacks the detail I put into this thread. I'm planning to add more JRiver specific info there. For other JRiver users.
Here's the link: Why I love JRiver, a tale of taming my Line Arrays

Another review, this time by DIYAudio member: Boden
Read it here...
Eelco dropped by for a chat about REW, JRiver and FIR filters and a short listening session. We talked about all things audio and discussed the DSP methods I use in this Monster thread.

Reviews keep on coming in, this time by xrk971
Find his kind words here
We managed to take advantage of a business trip to get both xrk971 and BYRTT together at my home.

It's raining reviews! Another one from BYRTT
You can find it here...
BYRTT was part of the get together. He's the only one to have heard both my lines and the insane effort from B&O, the Beolab 90.
I was very curious about a comparison.
Line Array Theory, a great read for anyone considering arrays
Infinite line source: analysis by werewolf

An old AES paper on Line Arrays, from speaker dave (David Smith), written at the time he worked at McIntosh:
Constant Beam Width Transducers line arrays

And as long as I'm adding line array papers: This original work of Jim Griffin is worth the read too!

ISO 226:2003 Equal Loudness Contour:
Interactive link with dB numbers
Amplifier tests!
The story starts here!
A big special thanks to member koldby and BYRTT. We had a small get together to do some subjective listening.
5 different amplifiers were tested with the arrays. I did not know what to expect, it was fun to be able to compare different combinations of electronics with the arrays. It seems that some combinations work better than others. I ended up having no choice other than to acquire the one I liked best.


A Picture with the new DIY Scan Speak 30W/4558T00 subs added:


The actual subwoofer build is scattered all over the thread, but here are some links:
Still making sawdust
Getting it together...
Did I screw it up?
Waiting for paint


Getting ready to paint...
Paint is on!
More info here: outside link (enough to make your own!)

And the new Fetzilla ambient amplifier that followed shortly after that:

The 15 Song Album collection:

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)

Il Penitente

yup, as I said , bad influence of Cyclotron emanation , all the way from Bubba Bob's Davis ...... 'Talian names popping as mushrooms after the rain

anyway, what's better to put on pizza than mushrooms .......

So, last one in series of autoformer gain amps (you can call them all - M2 on Mushrooms :rofl: ) , this one differing on outputs being classic BJT complementary pair, so sorta blasphemy in Papaland ......... he sinned heavily eons ago ....... while my Sin is recent........ :devilr:

Anyway, here's funny diagram, showing nothing else than bunch of multilegged fuses and some nice iron

hm, yes, my prototype equipped with first genuine ones I snatched from drawer - 2SA1491/2SC3855 ....... but pretty much any "for Audio amp" complementary pair should work well ........ 2SA1943/2SC5200 , TTA/TTC (newest Toshiba incarnation of 2SA/2SC)

rails +/-23V, Iq 1A5

2nd is clearly neg phase, not seen from my gigglywiggly, but I stumbled on nice routine in LTSpice showing just that behavior and didn't yet found reason to doubt it


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Alpha Nirvana 39w 8ohm Class A Amp

Hugh has been doodling on LTSpice and he came up with something really extraordinary: a 43% efficient SE Class A amp that can drive 39w into an 8ohm load with the usual Aksa-approved harmonic profile and low phase shift. The amp uses only 6 bog-standard actives and employs the excellent Aksa Lender front end to drive what seems like standard complementary MOSFET output stage using the venerable and easy to find IRFP240 and IRFP9240 outputs. However, it is not a push-pull amp though, but operates in SE Class A with an active CCS controlled by a cleverly wired PNP CCS controller. Please note that this active CCS is no longer based on the Pass Aleph topology but a PNP-controlled P-channel with symmetric sense resistors. The amp should really be called an Aksa Lender Nirvana.

So we have 4x TO-92's, and two TO-247 MOSFETs. Together, with only a +/-27v supply, they combine to make 39w into 8ohms with a predicted 0.019% THD AT 12w, and of course, always dominant H2 and a monotonically decreasing higher order harmonics. Output impedance is predicted to be less than 50mOhm at 12w into 8ohms at 1kHz and DF is 160. Quite a powerful amp given the rather low 27v rails. 27v rails happen to be what you get when you use an SLB PSU with a 22v trafo like an Antek AS-3222. Gain is 28.5dB, and phase shift is only 5.3deg at 20kHz.

Here is the rough schematic from LTSpice:

More detailed analyses and sims to come...

Later to be followed with the usual P2P vero-build, and then hopefully, a real PCB verification build and full measurements.


A huge thank you to Hugh for continuing to give us these gems! :cheers:

Edit May 25, 2020: detailed O-scope max power clipping tests by AndyR using his 4-ohm variant Alpha Nirvana with +/-21v rails:
Alpha Nirvana 39w 8ohm Class A Amp

Short story - good for 34W into 2.1ohms loads! Not bad for true Class A amp (cannot ever go into Class AB - it simply softly clips when pushed).

Edit Oct 31, 2019: latest version 2 schematic of amp

Predicted FFT with v2 for 2.83Vrms into 8ohm, THD=0.0039%:

And if we increase power to about 12.5w into 8ohm, we still see a nice monotonically decreasing harmonic distortion profile. THD is now about 0.016%:

Edit Nov 27, 2019: Measured max output before clipping is 51.6vpp into 8ohms, or about 41.6w into 8ohms. This is with +/-28.5v rails.





Edit Nov 29, 2019 - Grounding scheme schematic (post 279):

Produces background noise FFT like this:

Some measurements at 3.16vrms into 10ohms with a Cayin N3 DAP as 1kHz osc source, obtained 0.0041% THD and mostly 2nd and 3rd harmonic:

GB thread for this amp here:
Alpha Nirvana 39W SE Class A Amplifier GB

Tips and tools on how to do professional clean looking SMT/SMD soldering:
Alpha Nirvana 39w 8ohm Class A Amp

Edit Dec 14, 2019: BOM in easy to read .XLSX format:
Mouser Shopping Cart for BOM here. Do not modify cart - please save to your own shopping cart as a new project before changing.

Edit Jan. 3, 2020: please note that the Mouser shopping cart above needs to have parts for snubber boards increased by 2x as there are parts for 1 board only. The BOM is for one amp board so needs to be doubled for stereo. Double following: (R1001, R1002, C1002, V1001)

Edit Dec 26, 2019: AndyR did a lot of due dilligence to put together a very nice BOM for both the 8ohm and 4ohm versions of this amp here:
Alpha Nirvana 39w 8ohm Class A Amp
Thank you, AndyR!

Edit Apr 24, 2020 - Dual Monobloc Connection Diagram is using SLB and SFP boards:

As built schematic verified and tested to work:


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Old Maplin electronics magazines website with pdf's

Exploring Purifi Woofer Speaker Builds

With the group buys well underway the idea was bought up that a design thread be started to discuss build options.

Mine have arrived but I have no build materials and will not be able to get any until we come out of quarantine in (hopefully) three weeks time. I planned to start with a hybrid of purifi's SPK4/5 builds using the same AMT tweeter but maybe using a slot port with the 2.5khz crossover. That and I haven't done any AMT builds so it seemed like a good place to start.

I read of a guy in Aus planning on doing a line of passive and active speakers with the woofer so be interesting if he could chime in here.

So with no materials for the next at least 3 weeks, what better time to discuss build options! Fire away


Modded RPi4 Board for better SQ?

Hello since i readed much about audio lately i wondered if it would make "sense" to mod a RPi4 board for "ultimate SQ" (kinda like the allo usb signature)

things i came across so far that do "in theory" make sense:

1. replace the DC/DC Converters, one step further would be to provide the different voltages directly but i think thats a step too far, and someone also posting here said good dc/dc converter do make nearly the same effect (maybe add filter capacitors too?)

2. filter capacitors for usb, maybe as a sort of decoupling for all usb devices drawing power?

3. remove the BT/WIFI modul or disable it in some way, since even if disabled in config it still actively transmits

4. replace the clock(s) for better ones

5. remove the headphone amp circuitry and maybe other unneeded stuff?

any other ideas/suggestions?

Tim Curtis pointed out in the moode forum (where i posted this thread too) that it may be a good idea to use the CM4 + I/O board, this would make it possible to buy the cm4 without wlan/bt to begin with and has emmc on board if wanted (and in the end it costs pretty much the same as a normal rpi4b+)

i wanna focus on usb playback and the i/o board seems to have a good layout, the pcie x1 could be used for a usb 3.0 board to drive a ssd and things like wlan/bt dongle (so the usb 2.0 can be used standalone for the dac, its also a good thing i think that the usb 2.0 chip is very close to the ports)
tho im not sure about the hat performace with this kind of board (official i/o board) since it has rather long lanes/traces

i also watched around for other boards (there are quite a few) but couldnt find any that looks better than the official one, most have just too much unnessacary stuff or too few usb ports... i specially checked those ones -> (thanks for that jeff btw :))

any ideas/tips are very welcome :)

DAC AD1862: Almost THT, I2S input, NOS, R-2R

I reached the limit of 10000 characters in the first post and I am unable to continue with further editing.
There will be an article functionality:

For now, this link is holding the updated first post:


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Valve/Tuve HV regulator

I'm looking for a very good (objective & subjective SQ) HV tube valve base regulator, looking for information I see at AudioXpress the attached schematic but I need to know:

-Max. Vin & Vout
-Min. Vin & Vout
-Max. & min. current

I guess is a very good tech design, also I have on hand the valves & sockets, suggested ideas to improve will be welcome.



SynTripP: 2-way 2-part Virtual Single Point Source Horn

SynTripP© Syn·Trip·P (sĭn'trip-ē) n. The occasional tendency of two or more mental diseases to coalesce into one resembling or inducing the hallucinatory effect produced by taking a psychedelic compound.

The SynTripP© 2W2PVSPSH (2-Way 2-Part Virtual Single Point Source Horn) cabinet uses two B&C 10CL51 10" for low frequencies (LF) in an offset bandpass bass reflex arrangement with a Celestion CDX14-3050 three inch diaphragm 1.4" exit high frequency (HF) driver at the horn apex. The neodymium drivers and well braced 15/32" cabinet construction result in a very light and stiff (solid) enclosure, just under 34 pounds (15.5 kilos) for the 26.5" wide x 11.25" tall, 15" deep (67.3 x 6.075 x 38.1 centimeters) main cabinet which also incorporates an adjustable tilting stand mount adjustable over a 40 degree range.

The pyramid shaped second section of the horn is detachable, allowing the main cabinet to be much smaller and lighter than if it were included as part of the main enclosure. The secondary horn is 41" wide x 25.5" tall x 7.5" deep (104.1 x 64.8 x 19 centimeters), weighing about 5 pounds (2 kilos). The horns nest like Dixie cups, attached by a ratchet strap and bridle assembly to the main enclosure in about the time it takes to tie a pair of shoes. Dispersion is 86 degrees horizontal x 36 vertical, with pattern control down to 310 Hz (-6 dB 42.5 degrees off axis) horizontal and 460 Hz vertical.

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.

A pair of the main cabinets and secondary horns will easily fit in the back seat of most compact cars, The cabinet can be used without the second section in venues where size is an issue, without the second horn section pattern control is lost below 430 Hz horizontal and 1100 Hz vertical.

The SynTripP© design started as some rough pencil sketches years ago, then more recently progressed with modeling in the free Hornresp simulation program. Another DIY forum member, "xrk971" also modeled an approximation of the design using Akabak. Simulations are quite helpful, but there were several design details can only be determined by building, testing, and then rebuilding and retesting until the desired goals are achieved. One (of many) details specific to the offset bandpass bass reflex arrangement is how much effect the port size and location has on the HF response. Tests show that although the ports do affect HF response, the influence is rather minimal for the size ports ultimately chosen, while the benefits of having the LF and HF sharing the same horn make for remarkably good polar response. Each design iteration required extensive testing and crossover refinement, requiring drivers to be removed and reinstalled multiple times.

Sensitivity is defined as the sound pressure level (SPL) output at a voltage equivalent to one watt at one meter in a loudspeaker's nominal impedance rating, the SynTripP© is 4 ohms LF, 8 ohms HF. The sensitivity of 99 dB at 100 Hz (half space, 92 dB free space) is quite good for a cabinet of this small size, high SPL with "flea power" amplification is possible. Since sensitivity varies with proximity to boundaries (walls, floors, ceilings) and frequency, the raw response under varying measurement conditions and the equivalent SPL at "0 dB" is given below. The SynTripP© has an F3 of 82 Hz, so it typically would be used with one or more sub woofers, though in "step down" mode with one or more ports covered the response is adequate to reproduce instruments such as an upright bass at "live" sound levels.

No currently available commercially built cabinet incorporates all the features of the SynTripP©.

The SynTripP© design is a rather challenging to build, and incorporates features that may be of little interest to those with only a casual interest in DIY, but achieves accurate reproduction of sound heard in very few designs, regardless of cost or size. Elimination of some of the features more specific for it's intended primary application, live sound reinforcement, would simplify construction significantly without compromising sound quality for typical home use.

I won't bore you with extensive subjective flowery elaboration of the SynTripP's excellent sound characteristics, instead will provide actual measurements that substantiate it achieves the 10 design criteria listed below. After completing testing yesterday, listened to music at distances from about 6.5 feet (2 meters) up to 750 feet (229 meters) away, the cabinet elevated on a crank tower 4 meters high. Even at 750 feet the music could be heard clean and clear over the noise of Highway 14 traffic and a large backhoe digging in the Mineshaft Tavern's parking lot. The path of my bike ride while listening can be seen in the satellite photo below, the SynTripP© loudspeaker is near the telephone pole between the buildings in the lower center of the photo, the Mineshaft Tavern is the building in the upper right. The speaker was pointed approximately in the direction of the middle Highway 14 marker, it sounded great everywhere along 14 other than behind the large buildings to the East of the Tavern blocking the sound. Standing beneath the SynTripP©, discreet echoes from the various buildings could be heard, varying from about 600 ms to over a second in return time. To be able to hear those echoes when standing within two meters from the horn exit is a testament to the extraordinary directional control the SynTripP© exhibits.

Long and Boring History Time:
Just recently passed the anniversary marking 40 years of my adult life as a professional in the sound and lighting production industry, designing and building speaker systems, mixing audio for recording and in live settings for audiences ranging from 100 to over 100,000 people. During the course of my STS (Southern Thunder Sound) touring career I had the privilege of working with thousands of the best musical performers in the world, and directly learning from hundreds of the most experienced and knowledgable sound (and lighting) engineers. As well as learning from the best, I find that mediocre and awful engineers and sound systems give important insight into the difference between the good, the bad, and the ugly ;^).

Managing the technical, logistical and personnel details for as many 800 shows a year, fulfilling technical contract riders up to 20 pages long eventually lost it's appeal. After selling STS in 1992 (finally) moved south to New Mexico, built a home recording studio, and have continued providing production on a smaller scale, continuing to build speakers for a wide variety of unique applications, each using design aspects culled from a large palette of sound concepts appropriate for the intended use.

Part of the joy of DIY is the feeling of accomplishment after completing a successful project. The warm feeling can continue long after the project is done. Now that the cost of commercially available loudspeakers of (almost) all types has dropped to the point where their retail cost may be less than my cost just for the components needed to build them, I find little joy building something I could purchase for less money. Considering eating sawdust gets old quick, and the shop portion of a project usually turns out to be only a fraction of the time investment needed for design development, if a commercial product is "close enough", I'd prefer to buy it rather than build it, even if it costs considerably more.

Last winter decided to begin winding down from semi-large scale production to semi-retirement and sold my line array system originally built in the year 2000 (with a re-design in 2008). The line array system works great for it's main usage, outdoor events with audiences of up to around 5000 spaced as far as 400 feet away, yet was relatively small, light and could be effectively ground stacked, rather than flown.
I retained a smaller system suited for covering venues of around 1000 capacity. Although the conventional small format horn over woofer(s) speaker designs used in the (relatively) small system are fairly decent, they don't fully meet criteria that I have found crucially important for proper sound reproduction and playback. No speaker system currently commercially available meets all 10 criteria, so rather than wait for it to happen, decided to "DIY".

The SynTripP© design was developed to meet all these 10 criteria:
1) Flat and smooth frequency response to assure "what goes in is what comes out".
2) High output response to below 100 Hz so subwoofers do not need to be co-located with the main speakers, which are generally elevated. At frequencies below 100 Hz sound output (unless from a large array) is near omnidirectional, so the apparent sound image location does not wander between the sub(s) and main speaker location as it would with the higher acoustical crossover point a speaker with less low frequency output would require.
3) Smooth phase response, necessary for good transient response.
4) Wide dynamic range, the capability of reproducing levels equivalent to instruments such as brass and percussion which can peak in the 125-130 dB SPL (sound pressure level) range at one meter.
5) Low harmonic and amplitude modulation distortion at all SPL levels that will be reproduced. Quite a bit of even order HD can be tolerated, as musically it is simply doubling octaves, while odd order HD is much less tolerable, as it can change the composition, introducing notes not in the original. AM distortion, often (mistakenly) called "Doppler distortion" occurs when a driver's excursion exceeds the linear range of operation, which causes a change in level (amplitude) of the higher frequencies at the same rate (modulation) of lower frequencies. The effect is quite pronounced, making voices sound like they are gargling, and the onset is rather rapid after Xmax (the limit of linear excursion) is exceeded. Clean output at high SPL requires larger drivers with greater Xmax than would satisfy reproduction at less than "live" levels.
6) Low thermal compression during demanding musical passages. At high drive levels loudspeaker voice coils heat up, causing their impedance to rise. Amplifiers, being voltage sources, deliver less power at higher impedance, hence louder average signal results in less output than it would before the voice coil heated. As well as the thermal compression issues, large temperature rises result in a number of other driver parameter changes which can result in a drastically changed frequency response, especially when using passive crossovers.
7) Even SPL over a large coverage area. The low humidity here in the high desert causes high frequency air absorption losses (in addition to the usual 6 dB per doubling of distance loss) to be 10 dB or more worse than in humid environments. To make up for those losses requires as much as 10 times more HF power, making points 4, 5, & 6 more difficult to achieve.
8) Constant directivity (even polar response) with a well defined 90 x 40 degree coverage pattern over a wide frequency range, necessary for each listener to hear the same response. Well defined coverage "edges" are needed to keep reproduced sound out of unwanted areas to reduce reverberation and acoustical feedback caused when stage microphones "hear", and re-amplify the main speaker's output.
9) In addition to the above audio criteria, working in smaller venues (sometimes without additional set up help) and advancing arthritis in my left wrist (getting old sucks) require compact size and light weight, which made achieving the above criteria far more challenging.
10) Power is often limited in smaller venues, making high efficiency a necessity to achieve criteria 1-6, and energy efficiency is just plain good for the planet.

Criteria 1-6 are met by a number of commercially existing designs, though most of those choices conflict with 7-10.
#7 can be met using line arrays, but line arrays conflict with 8-10. Line arrays, having the "design feature" of a destructive near field interference pattern, dropping at 3 dB rather than 6 dB per doubling of distance, so can achieve a more even average SPL than a horn, but when elevated and angled down to the desired coverage area a large horn can actually achieve more uniform coverage. In either case, precise angle adjustment is required, hence the inclusion of the adjustable tilting stand mount in the SynTripP design.
Criteria #8 is the toughest to meet, as it requires a virtual single point source to achieve, and the waveguide must be large to provide defined coverage to a relatively low frequency. In theory, multiple horns can combine for seamless coverage, in practice, a single horn covering the desired pattern works better.

Co-axial speakers using a HF horn in the center of the woofer have been meeting most of the above criteria since the introduction of the Altec Lansing Duplex 601 in 1943. In the mid 1970s, Bill Putnam and Ed Long designed a crossover which time aligned an Altec 604, time aligned co-ax became the monitor of choice for many (if not most) large studio control rooms ever since.

A large studio control room is generally much smaller than a concert venue, to meet criteria 1-8 for large venues I developed the "Maltese" horn system in 1992, a pyramid shaped 3-way enclosure using a conical expansion HF horn centered in the mid horn centered in the LF horn. At 67.5" long with a 45x45" mouth, weighing around 350 pounds with a 13x13 degree HF dispersion pattern, around 18 Maltese horns would be required to provide the 90x40 coverage pattern of a single SynTripP©, which obviously would not fulfill #9. The nested horn concept has since been used by CSL, CV, EAW, JBL and probably many others, though none are as narrow dispersion as the Maltese.

During that '92/93 time period the introduction of Christian Heil's L-Acoustics V-DOSC line array using multiple entry HF and offset mid drivers sharing the same horn began to dominate the live sound market. It's fast set up time using less labor and slim form factor allowed more latitude in the placement of the increasingly popular (and progressively larger) video screens, ever more important in selling tickets, as (most) people go to "see" shows. Soon after, most every major speaker company developed their own versions of line arrays, each with enough minor variations of the V-DOSC theme to avoid patent disputes. Decades later, line arrays have "trickled down" and are becoming popular for home use, offering the same low visual impact that has made "column" speakers popular decades before they were commonly referred to as "line arrays".

Already familiar with Tom Danley's Servodrive sub woofers, on a trip to (or from) Florida sometime in that time period I stopped by the Intersonics lab in Illinois for a quick tour of the facilities, getting a chance to actually see his fascinating acoustic levitation device. Before this meeting, I had only seen a patent drawing of the levitator Tom had FAXed me after graciously answering some acoustical questions raised during the development of the Maltese system. I demonstrated to him the directivity, efficiency and "natural" sound of the Maltese HF horn with the tried and true method we old "hornys" still employ, speaking directly through the horn. After a quick description of the Maltese project, I was back on my way.

Sometime later, Tom developed his first line of single point source horns, the Unity (while at Intersonics/Sound Physics Labs) and then the DSL (Danley Sound Labs) Synergy, sharing the classic rectangular conical horn form developed by "Don" Keele in the mid 1970s (also used in the Maltese), but without the diffraction throat (and problems associated with it) that Don generally used in his designs as he went from company to company back then. Although the Synergy line has not gathered much traction in the large scale portable live sound sector, and with billions of dollars worth of line arrays deployed, won't for the foreseeable future, Tom's large Biblically named versions are doing well in both sales and performance, and are actually replacing line arrays in fixed installations in many sports stadiums.

Though the SynTripP© shares design features with some of DSL's and other loudspeaker manufacturer's offerings, nothing currently available specifically meets the unique requirements the SynTripP© fulfills. Even though at the rate I'm presently doing production it may take years before the use time will catch up to the design/build time, the achievement of the 10 goals made development of the SynTripP© worth it.

Post #9 lists the tests undertaken between 10/14/14 and 11/5/14, and DSP settings used with the horn extender. Post # 25 has a more detailed horizontal dispersion chart. Post #41 contains plans and a preliminary parts lists, Post #61 has the completed parts lists and assembly instructions, Post #100 has photos of the bass reflex port details, Post #115 has the throat port detail. Posts #128,138, & 568 have injection port and cone filler details. Posts around #729 have alternate HF driver options. Posts 897, 898, & 914 go into details of the throat adaptor plate and attachment.



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FS: Rek-O-Kut Rodine Jr with AT-1005 arm

I"m selling my trusty old Rek-O-Kut Rondine Jr with outboard motor. It has an AT-1005 tone arm in excellent condition and comes with a VM95E cart and also a Stanton 680 with conical stylus. This is a pinch roller type drive, but I use a little outboard motor which is much, much quieter. The original motor is still installed, but one of the idler wheels is missing (where did I put that damn thing?). New ones can be found.

The platter is nice and heavy and runs very smoothly on a ceramic bearing. The underside of the platter is coated with a 3M anti-vibration spray. The spray and the bearing significantly reduced rumble, and the use of the outboard motor of course made for a huge drop in noise. Silicon+Teflon oil for the spindle and bearing works well.
This is already a nice turntable, but with a better/stronger motor and maybe even a better plinth it will be excellent. The AT-1005 arm was a big upgrade from the original Grado tonearm. I'm the second owner. This turntable sat unused from 1974 to 2011 when I bought it and brought it back to life. Many hours of enjoyment and good music have been had in the past ten years. I'm sad to see her go, but it's time to say adieu.

Price is $125 which will be donated in your name to You pay shipping from zip code 33904. The box is 20x20x9" and weighs 24 lbs. It will be a bit pricey to ship if you are on the west coast.


Acoustic Horn Design – The Easy Way (Ath4)

Acoustic Horn Design – The Easy Way (Ath tool)

This is an associated thread for a waveguide generator called Ath (Advanced Transition Horn), version 4.
Ath is a piece of software for designing waveguides and horns. At the same time it makes it possible to easily simulate their acoustic behaviour by means of FEA (BEM) via ABEC/AKABAK tool.

The current release: Ath 4.7.0 was introduced in post #4898


Thread milestones (last edited 26.12.2020, no longer maintained):

#233 Birth of the OS-SE formula
Acoustic Horn Design – The Easy Way (Ath4)
Acoustic Horn Design – The Easy Way (Ath4)

#375 Measuring driver's exit wavefront
Acoustic Horn Design – The Easy Way (Ath4)

#666 Some of the practical verifications:
Acoustic Horn Design – The Easy Way (Ath4)

#844 Ath 4.4.1 - Introducing superformula
Acoustic Horn Design – The Easy Way (Ath4)

#922 JBL M2 "How-to"
Acoustic Horn Design – The Easy Way (Ath4)

#933 JBL M2 - Ath clone
Acoustic Horn Design – The Easy Way (Ath4)
Acoustic Horn Design – The Easy Way (Ath4)

#1003 Comparison of an OS waveguide and a flat piston
Acoustic Horn Design – The Easy Way (Ath4)

#1117 Ath 4.4.3 released (Fusion 360 import)
Acoustic Horn Design – The Easy Way (Ath4)

#1533 Ath 4.5.0 released (scripts not backward compatible)
Acoustic Horn Design – The Easy Way (Ath4)

#1602 General phase-plug discussion
Acoustic Horn Design – The Easy Way (Ath4)

#2389 Joining profiles of different curvatures
Acoustic Horn Design – The Easy Way (Ath4)

#2494 Tritona Waveguide
Acoustic Horn Design – The Easy Way (Ath4)
Acoustic Horn Design – The Easy Way (Ath4)

Spherical-wave phase plug

#1706 Initial ideas
Acoustic Horn Design – The Easy Way (Ath4)

#1824 Kessito's input
Acoustic Horn Design – The Easy Way (Ath4)
Acoustic Horn Design – The Easy Way (Ath4)

#1892 Compression cavity modal analysis
Acoustic Horn Design – The Easy Way (Ath4)

#2016 Diaphragm suspension analysis
Acoustic Horn Design – The Easy Way (Ath4)

Free standing waveguides

Acoustic Horn Design – The Easy Way (Ath4)

#2936 Rolling back the profile
Acoustic Horn Design – The Easy Way (Ath4)

#3390 Employing axisymmetric BEM (finally)
Acoustic Horn Design – The Easy Way (Ath4)

#3427 Rollback added
Acoustic Horn Design – The Easy Way (Ath4)

#3532 Source amplitude shading
Acoustic Horn Design – The Easy Way (Ath4)

#3549 OS-SE formula extended: k
Acoustic Horn Design – The Easy Way (Ath4)

#3664 Effect of an enclosure and other parameters
Acoustic Horn Design – The Easy Way (Ath4)

#3822 Compression driver throat plug
Acoustic Horn Design – The Easy Way (Ath4)

#4186 Preferred in-room response and DI target (discussion)
Acoustic Horn Design – The Easy Way (Ath4)

#4503 Incorporating compression driver model
Acoustic Horn Design – The Easy Way (Ath4)


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DS18 FRX2.5K resistor values

Hi all
Amp has plenty noise in the output. The resistors shown in the image with white circle burned. I would like to know the values of the resistors. The resistors with big white circle both reading 1.9k. The resistor with small white circle is open.
I tried with 10ohms in place of resistor with small white circle and it gets too hot but the noise reduced very much.


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What's an appropiate Powersupply for this 50w amp?

First of all, this is my first time trying something like this. I got my hands on a broken Logitech Z623(some of the electronics got fried) and I'm planning on using just the subwoofer as a speaker. I've been looking for a bit and found this amp that seems good to me. Now I'm not sure what to power it with. Perfect would be a mobile solution(battery), so I can bring this speaker places. But all I've been finding requires a cabled PSU(which can't be right lol).

Does anyone know how to properly power that amp? Sorry for the noob question

Hifonics Brutus BRZ1200.1D

When this type 7 amp came to me, it undoubtedly had had a reverse polarity issue. One of the reverse protection diodes (D2) was blown apart and it was showing a short from battery(+) to ground. Replacing the diode fixed the short. On power-up the amp went into protection. In checking, I removed the outputs (IRF640Ns) and the output driver card. I traced the protection issue down to the over-current transistor (Q283) testing bad. While waiting for my order of transistors to come in, I went ahead and replaced the 3 each PD2 transistors(U1, U2 and U3), 2 each 1D transistors (Q5 and Q7) and the 2 TL072 op amps (U4 and U13) for good measure.
After replacing Q283 and checking the PS, I reassembled the output section and everything looked good on the oscilloscope. I mounted it back into the heatsink and connected a woofer and music input. The amp maxed out and the supply voltage dropped. The woofer sounded "muffled" and had a lot of static. I connected my larger power supply and removed the current limiter. It did the same thing (the amps only got up to about 8A. I wasn't really pushing it).
I removed the amp from the heatsink to do more tests. I used 13.8vdc supply limited to 4.5A. My signal input (when used) was 50Hz at 2vpp. These voltage readings are referenced to the (-) speaker terminal. I also tried referencing the battery ground and got the same results.
With no signal input, I found that I had -3.42vdc across the speaker terminals when the relay clicked on. I traced that voltage back to the low side drains and the high side source legs of the outputs. The voltage appears when the remote is turned on.
When I input my signal, there was -2.5vdc on the the low side drain legs and high side source legs. When the relay clicked on, I had the -2.5vdc across the speaker terminals. When I removed the remote, the voltage across the speaker terminals went to -58.9vdc. I checked this seven more times. The voltage readings I got were 12.31, 33.2, -3.32, -58, 58.2, -59.2 and -32.4. These spikes only show up on the speaker side of the relay.
when I connect a speaker ( I tried non-inductive loads, too), I get 6vdc across the speaker terminals, the 4.5A power supply maxes out and the supply voltage drops to 9.3vdc The voltage does not spike when the remote is removed. The signal at the speaker terminals on the scope looks like a half rectified sine wave with the crest chopped off.
I am running out of ideas other than to put all new outputs in just trying to make it do something different,

Kef 107 Recent restoration

I have just completed restoring a pair of Kef 107R's that I recently purchased:
  • refoamed the bass drivers(used nitrile rubber glue, and replaced the rubber grommets in the driver frames)
  • replaced the caps in the driver crossovers and the tweeter/mid head crossovers (used original manufacture ALCAPS from falcon
  • replaced the ferrofluid (Ferrotech through springfieldspeaker)
  • The Kube is original, seems to work fine, and was taken apart and visually inspected with no apparent issues, therefore I have not replaced any components. (Question: Do the adjustable resistors / trimpots affect the sound if so how and if any risk to the Kube or other components if adjustments are made... the trimpots (red) are shown in the last pic of the flickr file)
-if anyone needs any additional info on the restoration work that was completed let me know

Attached is a link to some pictures of my restoration journey[email protected]/LuQ72h

The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB

Edit Jan 23, 2020: Connection diagram for single trafo and dual rail SLB with M2X amp
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB

Edit June 16, 2019: Error on Q5 orientation on Single Rail (SR) board. Please install Q5, BD139 with pin 1 to the square pad (as customary) but this will have front of part in contact with HS1. Ok to use smaller stamped aluminum finned heatsink here for back mounting. More info here:
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB

Edit June 12, 2019: in an effort to reduce my logistical overhead and efforts to pack and ship as track - I will be handling the GB2 via my Etsy shop. The SLB can be found here:
Smooth Like Buttah SLB Class A PSU | Etsy

I have been working on the development of a new power supply for Class A amps that really is quite a big leap forward from current designs used for so long. It utilizes an active bridge rectifier provided by the LT4320 and MOSFETs, followed by a precisely engineered CRC filter designed to match the load, and finally followed by a capacitance multiplier. The advantages that such a power supply will have include:

1. Almost no heat dissipation or loss through the rectifier
2. Improved voltage headroom since no 0.6v drop across the silicon rectifiers
3. Smoother inherent ripple from the rectifier since switching is active and time phased to occur at zero crossing
4. More compact since fewer and smaller bulk caps are needed
5. Lower overall cost since fewer large bulk caps are used (and we all know this is one of the most expensive parts of a Class A amp aside from the case)
6. Most importantly, improved performance relative to a traditional CRC supply with lower ripple and higher current capability.
7. The SLB provides a smooth and slower (1 second) ramp that may reduce speaker turn on thump. However, current in rush from the transformer being turned on is not prevented and a suitable soft start circuit such as the Soft as a Feather Pillow (SFP) SSR soft start can be used for a soft start.

You may say that the downside is that it’s more complicated - but for those of you going through the trouble of using 8 x MUR TO220 diodes with their requisite heatsink, insulator pad, bolt, screw, insulated bushing, snubber film cap, and tight spacing that makes assembly difficult - I am not so sure anymore.

Here is a photo of a single rail SLB portion of the amp (we integrated it as part of the amp for testing). You can see how small it is when using SMT variant of the active MOSFETs (mounted underside). Those are 15,000uF 50v bulk capacitors. Compare that to how usual Class A CRC or CRCRC supplies are using 22,000uF or 33,000uF caps. The large 3pin Molex connector allows us to place the cap Mx pass transistor anywhere we like and allows snappy assembly/disassembly from the chassis or heatsink:


Jhofland, Aksa, Vunce and myself have been working on a single rail prototype of this PSU which we are calling the SLB. The name says it all - Smooth Like Butter. Jhofland has been leading the layout and electrical design, Vunce and myself are doing the verification builds and testing of the performance and listening to the resulting music, and Aksa has been instrumental in providing insight and guidance, plus overal cap Mx topology design. It’s been a great collaboration and I feel that we have arrived at something really special and useful.

The design requirement was that it can flow 5 or more amps and have ripple in the single mV range (we are looking for about -60dB to -70dB ripple rejection) with a simple hookup of a secondaries from a power trafo. You then get clean mV ripple (sine like and not sawtooth) with a small adjustable output voltage range based on how much drop you want across the cap multiplier.

Regarding capacitance multipliers, we are testing 3 different topologies: Darlington, LTP differential (similar to the MrEvil design), and a new complementary feedback (CFP) pair with BJT’s. Work is on going but we are getting close to a downselect.

Here is the measured ripple (1.4mV rms) from the Darlington cap Mx with 4.35A load (37.5vdc output) with an 8ohm resistive load:

Under a real SE Class A amplifier load, the ripple is a bit higher at about 6mV rms with the Darlington topology, but still very respectable given a 4.35A current:

Our simulations show that the CFP topology should be even better. The LTP differential topology will be tested soon (tonight perhaps).

I thought it is now a good time to share the initial developments to get everyone ready for the SLB PSU. I hope that this compact little supply will be a useful new tool in your toolbox of Class A amps. It certainly provides some of the cleanest power Inhabe ever measured or heard.

Edit - here is layout:

Update May 5, 2019: Verification build test with 4.4A and 35.4v out and 3.1v drop gives about 1mVrms ripple with the SLB (with R17/18 replaced by jumper):

Here is the SLB vero build (v1):

Update May 6, 2019: Schematic and BOM of v2 (May 3, 2019) Production version of SLB here.. Pricing of SLB is $22.50ea (2mm thick FRP, 2oz Cu, ENIG finish, blue mask):

Edit May 6, 2019: Here is the SLB-SR (single rail version). BOM and Schematics here. Pricing on SLB-SR is $18ea (also 2mm thick FRP, 2oz Cu, ENIG finish, blue mask):

Edit May 9, 2019: Here is the pereformance of the SLB in single rail form as used on an actual SE Class A amp with 37.4v rail and 4A current. The top red trace is for a 10R value on R117 and bottom yellow one is 1.5R for R117:

Edit May 23. 2019: Production PCBs arrived.
Dual Rail

Single Rail

Edit June 5, 2019: Md_Stryker made a Mouser shopping vart/BOM for SLB v1.2 here. Please do not modify it - copy to your own project first!
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB

Edit Jan 23, 2020:
Connection Digram for a No-Hum M2X PSU with SLB and single trafo:

Connection Diagram for no-hum Alpha Nirvana:


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LDR Pre MkII - LDR volume control and I/O switching

The list of differences between LDR Pre MkII and original VxD LDR volume controller is so long that I thought it might require a new thread, even though LDR Pre MkII is actually a spin-off of amazing VxD from Vincent:

Arduino based LDR volume and source selection controller

1) Instead of Arduino Nano which runs on Atmega328P, LDR Pre is driven by Atmega328PB which can be found on some Chinese Arduino Nano clones. To utilise however the full power of "PB" which has three native 16 bit timers instead of one, Nano clone boards require hardware modification to expose additional pins on "PB", as well as new bootloader which uses serial1 instead of serial0.
2) LDR Pre has native 16-bit "DAC" capability, instead of 8-bit DAC in VxD. This allows smooth volume changes without impedance range switching which was causing volume bumps due to time constants in RC filters at PWM outputs.
3) LDR Pre supports only OLED with SSD1306/SSD1311, no LCDs any more. OLEDs from Aliexpress running on SSD1309 are not supported - I was not able to make them work over I2C.
4) LDR Pre has firmware which stores all the parameters in EEPROM.
5) LDR Pre fw has ability to change all the parameters from user interface, including: load and nominal impedance, screen brightness, screen saver timeout, welcome message, I/O names and LDR min values, max saved volume level, measured 5V voltage, etc.
6) Entire user interface is accessible by a remote or encoder. You can use only one of them or both to access all functions.
7) Backlight pin is now used to control power amp relay
8) Entire board runs on 5V. Built in Nano 5v regulator is not used any more, so less heat on the controller board. OLED now draws current from power supply directly instead from Nano.
9) Power supply is now delivering 3X5V instead of 2X12+8V.
10) There is no feedback code to maintain constant current in LDRs. I found this routine to cause more instability in impedance than environment temp, so I removed it. This allowed more room for additional code.
11) Since all the parameters are stored in the EEPROM, it's possible to deliver unified, one-size-fits-all precompiled firmware updates without involving Arduino IDE and all the hassles it carries. There is no need to have IDE installed at all to update firmware or change parameters.
12) Calibration routine has been changed and optimized to accommodate 16-bit timers.
13) There is an option in the menu to reset all parameters and names to default values.
14) Firmware is power amp friendly - it can be configured not to save volumes above max value stored in EEPROM. By default this value is 10 (out of 50).
15) Firmware boots into standby mode. Pressing play button on remote for 3 seconds turns on the device and powers up the power amp (if connected). Pressing it again for three seconds puts the device in standby mode again and turns off the power amp stage.
16) Pressing center button on (Apple) remote or encoder for 3 seconds enters the setup menu.
17) The code will be an open source eventually, but bear in mind that list of changes and patches in both IDE and hardware is so extensive, that even I don't remember any more which exact steps I took to setup a working environment, since Atmega328PB is not supported in Arduino IDE.

I will be offering boards for power supply and LDR Pre with modified Nano clones.
BOM is posted here:
LDR Pre MkII BOM - Google Sheets

PCBs for the project:


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What cartridge upgrade from a Shure V15 v-mr ?

I am considering trying a different cartridge. Maybe a MC. There is nothing wrong with the sound from this Shure MM.
Its just I don't know what more I might be missing.

If I moved to a MC I would also need a step up transformer.

The Shure has been highly regarded over the years, but would a change be a notable upgrade?

Budget, I suppose what it would take for a clear step up.

Linn LP12
I forget the model but I updated to their own light weight carbon arm a fews ago.
Ext. Psu

Yarqin Lesbox tube phono amp
Cary SPL50a preamp (upgraded)
Beard P50 tube amp (upgraded)
Rogers J149 speakers (just love the vocal ability of these) + 2 x b&w subs tuned to support.

Rare Mitsubishi MC-8000 - Amp Channel Issues

Hello DIYAudio

I have inherited a rare Mitsubishi MC-8000 aka X-10 ...
this is a Vertical Linear Turntable with a builtin Amplifier/Tuner/Cassette !

Date of build is 1981

Problems with its amplifier -
Appreciate any help I can get to get this working and keep it out of the trash!

Was told it powers up ok when it was given to me -
- however on power up the Right channel is silent.

Left Channel worked sort of - Sound could be heard but then the volume decreased and static heard - this happens intermittently
and at the same time the volume decreases the units VU Meters lamps would dim.!

After dissasembly I found right channel output Fuse F821 3.15Amp Blown

The Amps IC is a Sanken Dual Channel SI-1135HD - I believe these have been used in other Amps (Rotel) Only a couple on Ebay I could find
(however are they fake?)

Thanks in advance for replies - what are peoples thoughts... how best to test/check the module? - approach to finding the exact problem given the symptoms?

If it turns out to be the Sanken SI-1135HD wonder is a comparable alternative IC Amp available ?
Suppose if not and its the Sanken then I could try and retro fit a Class D Amplifier Module...

Any thoughts on the above most appreciated


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Old Soul

I'm tired, long day

So, not too much babbling , for change :clown:

Objective: make it before Pa, and (normally) make it more complicated than Pa

What: amp using Germanium Biguns


edit: while I was dreaming about and working on this amp, I was often thinking about Pa's Joe and Jack

friendship, love and appreciation are very important parts of life

edit on 24. April 2021: THD measurements with 1T813 ( USSR!) instead of 2N1099 , post #68 Old Soul

edit on 15.09.2021 - few general setting procedure tips and tricks; be sure to read to the very bottom of post:

-will not teach ya how to solder everything properly - as always -Assembly of Japanese Bicycle Require Great Peace of Mind

-prior to powering up, be sure that you have trimpots set properly:

P102 (P202) - irrelevant
P101 (P201) - set to max; confirm with ohmmeter across R104 - in vicinity of 28R
P103 (P203) -irrelevant
P104 (P204) - set to min ; confirm with ohmmeter - improvise where to put probes

- jumpers JP101/201 - open/not mounted

-as always - best to work with one channel connected to PSU at time; in fact - first step just one channel , in second step - you can freely leave powered/connected already set first channel

- one VMeter across output ( DC offset) , second VMeter across any of current sense 0R22 resistors; use mini-clips/probes

- no load on output, input shorted to GND

- power up thingie; observe DC offset - it will rise slowly and everything up to several volts is normal in this moment

observe VMeter across 0R22 resistor - it will be Dodo reading for some long time; after 60-90-120sec - if you don't see any substantial reading , start fiddling with P104 (P204), one turn at time; of course - you did remember where you rotate itr to set to min value, now rotate in counter direction; - don't ask me which - I don't care, I can't remember, simply because I'm always trusting in DMM, not in my memory how to orient damn trimpot to have screw in proper place ....... and my logic what needs to be decreased and what needs to be increased is always ooked, vs. overall consensus :rofl:

allow 30sec or so between 1-turn steps, to observe when and how much mV you're getting across 0R22

goal is , , say for 1A of Iq - 1A * 0R11 = 110mV

keep fiddling to get mV creeping up, and once when you see steady rise for each turn, set da thingy to - say 80mV

(if you're using Si Bigun in place of lower output, feel free to go to 1A5 as target, pre-set to 1A3)

once when you're there - fiddle with P103 to get as close to 0mV of output DC offset

that would be preliminary setting of OS, now to input buffer setting :

- power off , put mVmeter across R106(206) test pins ; put second mV meter on jumper pin marked "B" and GND

power on, fiddle with P101 to set 20mV across R106(206) ; done - fiddle with P102(202) to set as close to 0mV for buffer output offset ( second
mVmeter) ; when done - power off, close jumper

*************** connect second channel to PSU, repeat entire procedure******************

when done with both channels , power on , re-set Iq of both channels to have 1A ( thinking mostly of life of venerable Ge - but don't fret - Square Law OS is crazy thing) somewhere in temp equilibrium, check output DC offset

slide of both Iq and DC offset - cold vs. hot - is really minimal, but I'm mentioning thermal equilibrium more thinking of importance of final temperature of heatsinks - observe, observe also temperature of outputs , that will give you info/confirmation how good and uniform is thermal interface between parts and heatsink


when done, connect signal, speakers, flip da switch, and enjoy

don't forget Da Porn - no Porn, no Glory



pinout of 2N1099 is in post #299



M101/201 not having type on schm - it is IRF9510



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what driver should i choose? the F15 or F18 from lii audio

hello everyone i want to do a fun and easy project an open baffle speaker, the first Diy project in my life, i saw the lii audio f15 and f18 and they amazed me by the dimension, my question is what driver should i take? the 15 or 18? my concern is that the 18 will be much bigger with the baffle created, is there a better driver between the 2? help me pick one, thanks!!

i am more oriented to the 15 as i read that is a little more equlibrate, and will not need an huge baffle

Current best 5" midrange driver?

It's a 3 way so it doesn't have to go very low. There's plenty of amp behind it so high efficiency isn't a priority. Transparency, low distortion and detail are the requirements. A slab flat frequency response isn't a huge requirement either.

I was going to use an SB15CAC30, which matches my criteria on paper, but apparently it isn't very transparent...

What's the flavour of the month?

DATS V3 - Windows 10 issues

Today my long awaited DATS v3 was delivered.
Nice small footprint case with a supernova blue LED to ensure your neighborhood knows you are testing speakers ;)

Downloaded the most recent software from their homepage but ran into the same issues as last mentioned in 2018 with the DATS v2.
The speaker and mic setting are correctly configured, privacy settings - all programs are allowed to use the mic.

Wanted to start the lead calibration but got the warning message "no sweep detected"!
Tomorrows job is to check my basement for wifey's old Dell with hopefully a running Win7 OS.
Are there any other users with the same issues?
At the moment I'm a bit lost.

Thanks in advance for any tips...

Subwoofers for Magnepan LRS

Having purchased Magnepan LRS's, which I'm completely blown away by, I thought I'd try adding two subwoofers. Although the smallest Maggies, they were quite confronting (I've got used to them now and don't even notice!) so my preference for open baffle subs to best integrate meant putting up with equally imposing stacked H frames till I discovered Mr Linkwitz.

I built a pair of Dipole Woofer 3's slightly modified (not in dimensions) for ease of construction and practical shape/finish/use. Cutting sheet for 18mm MDF 2400x1200 and construction photos available by email.
They are yet to have top veneer and grill cloth frames but photo shows neat size (KEFs in background are retired). They use a pair of 12" OB woofers (BIANCO-120B150) per channel. Very inexpensive approximately $500US all up including materials.

I used this inexpensive low pass filter leaving the LRS's full range on their own monoblocks.


I've not got any measuring equipment but they integrate very unobtrusively and smoothly into the LRS's. I've used a test CD running c/s 100 down to 20 and there is a smooth transition from LRS's to subs. Musically they match, only reinforce and do not dominate. I'm a retired classical musician so I have good ears!


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Introducing the Hermes-Amanero

Hello Folks,

You can get the Hermes-Amanero (along with the Cronus/Rhea) here:

Cronus Reclocking

This module allows you to use the Amanero with the Cronus in a fully isolated manner with the Amanero in slave mode - and the Cronus providing the audio master clock.

This give you an ideal isolated USB audio solution that supports PCM/DSD(via DoP implemented in the Amanero)

All frequencies from 32Khz to 384Khz are supported and transitions between 44.1 and 48Khz sample rate families are seamless.

I am currently (and strongly recommend) using the following configuration.

45/49Mhz clock with Hermes clock output set to 1:2 - this means the Amanereo is sourced with 22/24Mhz - while the clock for reclocking (and optionally the DAC) is 45/49Mhz.

CPLD Firmware = "Slave_For_1080"
CPU Firmware = "firmware_1096c" or "firmware_1095b" - but do not use "firmware_1095c" as it is broken.

Hardware setup is very simple - just connect the appropriate headers and stack the Amanero with the Hermes (either on top or bottom depends on your needs) Then stack the Hermes (once again either top or bottom) on the Cronus. This makes the interface very clean and short - and at the critical point (the Cronus outputs) everything is time aligned with the Cronus master clock.

I have tested this combination in Windows using Foobar and on my MacBook Pro using Vox and other players.

PCM and DSD both work fantastically and play lists that move between sample rates and DSD/PCM types work as expected with no pops (using a B3SE) or any other nastiness. The highest sample rates work perfectly (352/384khz) with the firmware indicated above.

I am very pleased with the result - and since everything is perfectly time aligned with the Cronus clock from input to output the audio signal is clean and pure. No data errors - no data loss - no isolator induced phase noise. With Hermes/Cronus there is no need to for anything else between you and music.

This is not really simply reclocking - it is in fact simply a perfectly time aligned USB source.

This is the simplest way to use Cronus - and works very well even with usb hosts like the rpi-2.



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Cronus - It's about time.

Hi Folks,

You can find it here:
Cronus Reclocking

Cronus is a module designed for providing clocks to and reclocking output from digital sources. Cronus forms the backbone for audio sources built around 2 other module types - Hermes and Rhea.

Cronus was a long time coming - because we worked hard to make the results not just good - but superb. We could have released earlier - but we wanted to get in all of the things we desired after two prototypes.

Special thanks to Miero for his beta testing.

Extra special thanks to Brian for being patient with my long design process - and for putting together awesome beta and production kits.

Cronus provides the following:

  • An ultra low noise low impedance 3.3V power supply for clocks and reclocking section.
  • A clock selection multiplexer to switch between 44.1 and 48Khz time bases.
  • A selectable/bypassable ultra low phase noise clock divider to supply 1:2 or 1:4 clocks to a source.
  • A synchronous reclocker that re-clocks the audio from the source back to the master clock. This brings all signals back into alignment with the actual master clock regardless of source jitter - thus your final signal is as good as the clock you supply - which is to say - excellent!
  • Pads for pluggable clock sockets based on standard DIP(8 and 14) clock - See Rhea thread for more details.
  • An interface for connection to our isolation modules for various sources - See Hermes threads for more details. Hermes isolates your DAC completely from your source.
  • Interfaces for connecting to B3/B3SE and any other PCM/DSD DAC.
  • SMA and uFL connectors for external clock signals (both in or out)
  • uFL connectors for PCM/DSD output.

Some useful things to keep in mind:

The re-clocking section makes use of a Potato semi FlipFlop. When using a FF in this way the frequency of the clock input supplied to the FF must be at least 2 x any signal. For this reason ~22-24Mhz family clocks can be used for PCM signals up to 192Khz - for up to 384Khz you must double that. The device is capable of up to 768Khz PCM.

The module is designed for around ~5VDC input - but it is fine to go higher (absolute max is 16VDC) depending on the load you are putting on the VREG (adm7150) please refer to the datasheet about limits. The max current is listed at 800ma. The current consumption will vary depending on loads and audio frequencies. In testing using Crystek clocks (50Mhz family) I am drawing well under 150ma at 384khz. Keep in mind also that Hermes modules are designed to be powered on the clean side by the Cronus power supply.

The clocks are isolated from each-other and the rest of the circuit by utilizing L/C filtering with ferrites.

The Cronus is designed to work with Sources that provide a clock selection signal (CS) and can accept an external audio master clock - it is currently tested with two Hermes modules. Hermes-BBB for the BeagleBone black (using Botic distro), and the Hermes-Amanero for the Amanero USB module. There will be a thread for each. Both are tested and work up to 384Khz.

I will fill in more details to this post as necessary.

A manual is under way for each module - but I hope you basically know what you need right now. :)

The Hermes and Rhea threads will fill in a lot more detail.

I have also attached the pinouts of the .1" headers on the output side of the cronus and the Hermes header.

Note: If you use the terminal blocks - it is recommended to mount them on the bottom side so they don't interfere with uFL connectors etc.

Ask away!


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Low distortion amplifier (LDA) non-profit kits


I have a low noise, low distortion distortion transistor audio power amplifier design. Built 2 mono and 3 stereo prototypes so far that work fine. This is a DiY design, but I believe it was more carefully tested under non-ideal conditions than the majority of DiY designs we encounter on the internet. The 1 kHz THD was measured 0.0006%...0.0013% on the prototypes depending on power level and load (loads down to 3.5 ohms, output power from 0.2 Watts up to 200 Watts /3.5 ohms). Below 0.2 watts, distortion harmonics are masked in the noise floor of my equipment even with averaging. Other kind of more challenging distortions like 19+20 kHz IMD and TIM(DIM) -- see images -- are low at all power levels and at all permitted loads. Capable of 200 Watts/ 4 ohms or 110 Watts /4 ohms output power depending on component set.

A nulltest (google "audio nulltest" if you don't know what it is) showed that the amplifier has no audible distortion at normal listening volumes, so it can be considered as totally transparent sonically. (Well, I understand some people like audible distortions if they color the sound pleasantly or interestingly. So this amp is for people who rather like reality.)

My open-ended offer is that I send you the kit you choose (one of the 4 different kits that are available) at a non-profit price. This means you'll get the specified PCB's and components at the price I bought them, and I won't charge my wage of labor either. I do this to make this design and the kits more popular among DiYers. I only ask in return: please give me feedback how I can improve the completeness and quality of the online information, especially the assembly instructions.

All kits contain the low distortion power amplifier board(s), power supply board(s) and protection board(s) and the components to populate the boards as covered in the online documentation. (User selectable components like chassis, main heatsink, main filter capacitors, power transformer(s) etc. are not part of the kits.)

The home page of the LDA amplifier is this, where you'll find links to all information that is available right now (kit descriptions, specifications, assembly instructions, some measurements and listening tests):

LDA home

The circuitry is more complicated than the majority of DiY projects, it is not for beginners. If you don't have proven experience in audio amplifier construction, please don't buy it! (If you make a mistake and some components are blown, I can't help in troubleshooting, I can only resend the whole component set for the faulty circuit at the non-profit price until this sale is offered.)
The LDA MIN_np kit is the simplest and cheapest (2x100W stereo) kit of the 4, it has only a minimalist protection circuitry. The LDA 53DM_np kit is the most expensive and most reliable (2x200W dual mono) kit; regarding protection, it survived 3 output short circuits during the testing without degradation of output signal quality due to the fast acting ultra low distortion solid state relay in it.

You must pay the shipping costs, which may be significant outside of Europe (shipping is from Hungary).
Right now I have in stock components for 4 mono amplifiers (or 2 dual mono or 2 stereo). If there will be interest in more non-profit kits than this, then I'll need about 2 weeks to buy the necessary components.
Most of the kits are available on the German and UK ebays and some of them on the Hungarian The price there contains the fee I need to pay ebay or vatera for the transaction.
If you are in the UK, in Germany, in Hungary, or in an English speaking country where ebay is present, then you can ask me to list your chosen kit on ebay if it is not listed.
If you're in another, non-English speaking country, I think you should transfer the non-profit price of the kit + shipping cost to my PalPay account in advance, which you could rightfully consider unsafe. Still thinking about registering on Amazon...

If you have any question, please ask.

[The image shows only the amplifier board without the output transistors and the tempco transistor. Those transistors are also part of the kits as well as other PCB's with the components specified in the assembly instructions, which, in most cases, are all the electronic and mechanical components that populate the PCB's.]



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Pioneer VSX-LX51

Hi everybody
Here to ask for a bit of help and advice regarding this 7.1 home cinema...
Completely dead apart from blinking blue LED at the centre of the amp (HDMI 1/HGMI 2) and doesn't wake up after reset procedure.
Traced aux (stand by) voltage all the way to the main controller on the front panel and found to be correct including the signal from the "on" button.
After much head scratching and looking at the service manual I found that the "Wake Up" voltage from the aux power supply is low but not sure if it is (are) my voltmeters at fault.
Can someone help a depressed member before I scrap the thing....

PS: Yes I disconnected the flat cable and the voltage didn't change


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New Monoblock chassis (sets!!!) from Modushop

Well, I'm certainly not first one to ask Modushop Team is there solution for slim Monoblock case ..........
Anyway , recently I did chat with our Italian friends ...... and thet are evidently willing to do something

Basic idea is to have 4U/400 case, but narrower

Entire package, (hoping they did understood my ZMEngrish) consisting of 3 iterations:

1. first logical iteration is one side having 4U/400 heatsink ( I don't care is it one piece or two) , while other side being blank plate ; you can orientate it by wish, so wth pair having one right and one left enclosure

2. second logical iteration is heatsinkless case, intended for separate PSU ( don't ask, I'm first one thinking of pair of cases per side, just as Demonstration of Force, if not necessity) ....... so penny-pinchers among Greedy Boyz can make one (pair) of mono PSUs and zillion of channel cases, then combine them Till End of Time

3.third logical iteration is both sides having heatsink, so you can squeeze nicely thought elegant Beauty of Amp inside ........ from whichever reason - easier to smuggle by Kerber, or esier to put more of them on shelf ..... or you just like them that way

set of preliminary pictures enclosed, raw finish, not anodized .........

my Vote goes to front plate (as usual) covering entire width, including heatsinks

What ya say ?

Basic dimensions are sorta carved in stone ( zillion Greedy Boyz, zillion and one opinion) so don't bother to change that; what I'm asking now is - what you say for width of front plate ........... and do you have any (useful and beneficial!!) idea to add?

Unification reasons (price for Greedy Boyz) - dimensions of "cage" itself must be the same for all 3 iterations;
Now - I like idea of full width front for case with one and 2 sinks, I like the same for heatsinkless one - when looking them in pair, and I'm sorta ambivalent when thinking about empty space behind wide front plate without sinks; so...... as always - compromises.........

I'm sure Gianluca will chime in, to give you details about width of case ...... I deliberately left that for him

And yes, 'Talians - Danilo Petrucci is first man alive, after having 2 MotoGP victories, also claiming victory in Dakar stage for motorcycles

Go figure; it must be something in the air or water, in Italy


edit, much later: one thing I did forgot - having base plate for these is also important detail .......


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Autoranger for soundcards


Thread edited to keep chronological order of moved posts.

Introductory note from Jan carried forward from old thread.

Since I started my design for an autoranging attenuator/amplifier I have been posting in other threads sometimes hijacking them. So I asked the mods to collect those posts in a new thread here.

Comments invited.



Hi hochopeper,
If it's a 100 KHz source you need, an LC circuit could make an effective filter to hang after a crude sine wave source. Any of the HP oscillators like the 3336B or 3325A or B would serve quite well. Digital frequency accuracy, digital level stability. The L-C filter network would really do a number on distortion products.

Any of the XR2206 type circuits could also be used with a drop in stability, but still probably better than you need.


Hi anatech,

XR2206 looks like the go, thanks! It's times like this that I regret not buying the -S model when I bought my Rigol scope.

Another milestone in the development of the autoranger!
Finalised and tested the cal procedure.
Especially calibrating the freq response for 0.1dB flatness out to 100kHz is a challenge if you don't have a fully equipped lab :eek:

I now have a procedure that needs only an AC DMM with reasonable performance and a signal generator that can output 10kHz and 100kHz, preferably up to 10V or more but that's not critical.

The procedure directs you to do some measurements and enter values in a small spreadsheet and the spreadsheet then tells you what to adjust (cap trimmer) for which DMM indication.
For -20dB and -40dB settting, in both SE and BAL mode.

It's done faster than described!



In your note above you mention a source that can provide 10kHz, 100kHz at ~ 10V ideally for calibration. The cheapo XR2206 kits seem to be set for 2V sine wave output. The datasheet has mention of changing a resistor and increase supply voltage to 25V to get more voltage out so no worries there. I don't want this thing to cost any more ($$ or time) than it needs to, should I care about the 2.5% distortion for this purpose? Or should I look for something a bit more sophisticated?


Introducing the Buffalo III-SE-Pro 9028/9038

Introducing the Buffalo III-SE-Pro 9028/9038

The Buffalo-IIIse Pro (Stereo Edition) 2-Channel DAC

Brian and I have had access to samples of the ES9028/38 DAC chips for over a year and half now. Of course - we were very excited to give them try. And we did - but we found that early samples from ESS had a significant defect that made evaluating it very difficult on our current platform, thankfully those issues were soon resolved by ESS and new samples were obtained. We then began design/prototyping in earnest. In the meantime we have been getting questions daily about when we will release new modules designed around the new DACs. The answer is we are releasing one now - but please read on because how we got from there to here is important.

There is a lot of greatness in these two new chips. First the over-sampling filters and IIR filter are much improved over the ES9018 - and I am not overstating this - you will absolutely hear the difference between the various filters and you can select the one that work the best for your particular application or taste. The new DACs have the following filters:

8X FIR filters:
  • Brickwall
  • Hybrid fast roll-off minimum phase
  • Apodizing fast roll-off linear phase
  • Slow roll-off minimum phase
  • Fast roll-off minimum phase (default)
  • Slow roll-off linear phase
  • Fast roll-off linear phase
8X IIR filters @ 44.1Khz:
  • 1.5874fs - 70K
  • 1.3605fs - 60K
  • 1.1338fs - 50K
  • 1.0757fs - 47.44K(default)

You can see the responses and read more about the filter in the datasheets. We expose all of the built in filters in the current on-board firmware. So you can experiment and see what you like for yourself.

The ES9028/38 “Jitter Eliminator” technology itself has undergone some very important changes in regard to how it can be configured - including a new sync mode feature. It also has some interesting configuration around trade-offs like initial lock speed and DPLL bandwidth that are completely new compared to the ES9018.

We also realized that there is a lot that the current Buffalo III-SE module delivers that we have found DAC builders really like. We wanted to keep those features - they include:
  • A simple consumer level SPDIF input option by incorporating an on-board comparator
  • Simple intuitive stereo/mono PCM/DSD inputs - no summing or remapping required
  • All of the configuration inputs are exposed on a header so that switching of certain features can be done either with the DIP switches on board or remotely - say at the front or back panel or via a second controller.
  • Optional ADC driven volume control for precise but simple operation.
  • Easy stacking integration with existing and new output stage modules like (Mercury, IVY-III, Legato) which are using the current module form factor and spacing. Individual independent voltage regulation for the Clock, Digital, and Analog sections of the DAC - designed for Trident and AVCC modules.
  • The ability to reuse your existing power supplies (as long as they can supply a steady 5VDC) like the Placid-HD or the LCDPS.
In addition there are some very important new features we wanted to be sure the new module supported (with appropriate firmware):

  • Improved digital input scheme (no more ES9018 style remapping and summing)
  • Added GPIO support from the DAC including mapping them as various inputs
  • Output gain calibration for multi-DAC use cases including Mono operation
  • Exposing the new Hyperstream II sampling modes (sync/async)
  • Exposing the capability to run the DAC in either master or slave mode.
  • Support for remote clock and data I/O using uFL connectors.

The digital and control aspects of the ES9028/ES9038 DACs are in some ways similar to the ES9018 - but in many more ways are a significant departure from the venerable (and still excellent) ES9018. Quite simply the ES9028/ES9038 could never be considered drop-in replacements for the ES9018. Still - what Brian and I wanted to do was present a module that could both allow reuse of already excellent I/V stages like the IVY-III and the Legato when using the ES9028 while still allowing the user to opt for the ES9038 when paired with the new Mercury output stage. Yes - you are reading correctly we have an output stage that will absolutely handle all of the current of even a mono ES9038 - in current mode! So users have nice DAC upgrade path without ditching what they already have.

It is true (as I have stated in other threads) that the ES9038 in particular presents some particularly interesting design challenges because of the sheer amount of current it pumps out to the I/V stage. Presenting a virtual ground (so that the DAC operates as a current rather than voltage source) to that much output current is no small challenge. One of the reasons we have held off releasing a new module based on these chips was precisely because of the demands of the ES9038. The good news is that what we discovered actually benefits all of the ESS9018/28/38 DACs (yes - even the ES9018) and our patience has been rewarded in a solution we can truly be proud of.

So what we are presenting to our users is the ability to use existing excellent output stages with the ES9028 - variety is good! As well as a new output stage that is also suitable for the ES9038.

The ES9028 and ES9038 are practically identical except for the analog output section - which is duplicated 4 times and connected in parallel in the ES9038. The ES9038 was clearly designed first and foremost for 8 channel operation - but works well in stereo and mono mode as long as you have an output stage that can handle its copious current. We have tried two approaches to the ES9038 and will actually be supporting both eventually. First you can sum channels at the DAC - this is what the B3SE-Pro does. Second you can take all 8 outputs and sum them after I/V. This we have also tried and it also works quite well - but is also very expensive and huge! Also, after trying both we found to our (pleasant) surprise that compared to summing at the DAC and I/V with Mercury the result of summing after I/V was almost identical!!! There is no compromise in summing at the DAC as long as your I/V stage is up to the challenge. Now if you want a compact 8 channels of bliss - the ES9038 is indeed awesome - so at some point soon we will release a new 8 channel DAC call Buffalo IV based on the ES9038. It however will be a completely new design and thus will not be as simple to integrate with existing I/V stages etc. That DAC module will also allow you to sum after I/V if you so desire.

So there you have it. After much testing and designing a whole new output stage to meet the challenge we are ready to present to you the Buffalo III-SE-Pro. We are taking orders now for the module along with a new series AVCC and Tridents which are redesigned to take on the rigors of the increased current demand of the ES9028/9038. We also made the new trident available in a broader range of voltage output. This is important because in cases like running the ES9038 in mono at high sample rates, you want to run VDD at a slightly increased voltage than the nominal 1.2V). The ES9038 recommends 1.3V when running high sample rates in stereo/mono and we offer that voltage. I actually found that the ES9028/38 all seem to operate better at 1.3V VDD. We also found the running the AVCC module at 3.6V is desirable (because it increases the output swing slightly) - so we configure it for that voltage.

Please ask any questions you have about the new DAC modules and the Mercury - I am sure I forgot to mention something - though keep in mind I will be opening a new thread when Mercury is ready for us to open orders. Mercury is actually finished and is only awaiting final testing of the production PCBs - the circuit itself is finalized. We have just received the production Mercury PCBs and we will be testing them this week. Mercury is the spiritual sibling of CounterPoint - and is essentially the same idea - it is exactingly purpose built to maximise the potential of the ES9018/28/38 I can’t wait to introduce it to you in more detail.

I am working on the datasheets for the new modules and I will make them available very soon. They are very similar to existing modules so most users should be able to hit the ground running. The most important thing to remember is that the voltage input should be right at 5V - please don’t exceed that by more than a half volt because of the relatively low maximum voltage of the ADM7151 regulators in the Trident-SR and AVCC-SR that we recommend for this module.

Things we created to get ready for B3SE-Pro

  • Trident/AVCC-SR Local Regs for B3/B3SE/B3SE-Pro Trident and AVCC headers - Trident-SR
  • B3SE-Pro Module
  • Mercury Output Stage
The Buffalo-IIIse Pro (Stereo Edition) 2-Channel DAC


DIY Schroeder Tonearm???

With all the recent talk about unipivots and such, has no one ever considered knocking off a magnet stabilized string pivot like the Schroeder? I have been considering a DIY arm just to add a mono cartridge to my TT. This implementation "looks" fairly simple :scratch: Assuming you have a source of wood and carbon fibre, the only things slightly out of the ordinary are the neodium magnets, which are fairly ubiquitous on the web.

See pics and a review of the Schroeder's stuff at his website:


Rotel RB-1590

I'll be taking possession of a couple of Rotel RB-1590 power amps shortly, to drive 4 passive subs (2 subs per stereo amp).

Each sub houses a 4-Ohm dual voice coil driver. So, I can configure the subs as either 2-Ohm or 8-Ohm loads.

Hifi News measured the RB-1590's dynamic output as follows:
- 565W into 8 Ohms
- 870W into 4 Ohms
- 455W into 2 Ohms
- 235W into 1 Ohm

So clearly, I will configure the subs as 8-Ohm loads.

But I'm curious...

Although the amplifier is capable of outputting around 50A, Rotel use a current-limiting circuit to limit the current to only 15A max.

I understand that the current-limiting circuit will protect the amp should a short occur.

But did Rotel really need to 'throttle' the amp so badly?

All thoughts welcome.


Dead Script panel, need some help from the knowledgeable folks here if possible

One of my script panels quit functioning. Did the basics, switched power supplies and the panel worked fine. Narrowed it down to the power supply. Started with the 6 10k resistors on the board. A few were out of spec, so replaced them. They were not far out of spec, the worst being 11.47 and 10.67 and 10.53. New values are all within 5%. Next went to the transformer. I followed some of Bolserst's great troubleshooting advice. I was reading through his posts and his knowledge is amazing....

I measured the voltage output of the power transformer that feeds the HV multiplier. This seems high at 274 Vac, so not sure on that.
Next I measured voltage at c12. Did this with music being fed to the speaker. If I turn on the power and immediately test, it jumps to 1227 Vac and then steps down to zero. One second later it jumps back up, and steps back down. It does this for a couple mins and then holds steady at .90. Maybe I should be testing DC? I do not have a super expensive DVM, but I have always found it reliable.

The red light comes on and stays on for about 2 mins, then goes off with music being fed. Dont know if this is important.

Really love these and cannot afford $300 for a new board, so trying to DIY, but its beyond my knowledge at this point. Can anyone point me at other things to test? I would be extremely grateful. If I can isolate the bad part, I have enough skills to replace it.

Thanks for any help you can provide.

Acoustic Energy AE1

one of my AE1s has gone kaput.
The mid/bass voice coil is rubbing, well more accurate to say, almost locked solid.
It must have overheated and on cooling became distorted.

Does anyone know of a replacement driver that fits the cornered rebate and is a good substitute for the T/S parameters of the original?

The last time I replaced a driver, Acoustic Energy took £75 off me for an exchange unit and that was about 12years ago. I don't even want to ask their price for one now.

Pictures of your diy Pass amplifier

Hi everybody,

this is a special request, as the gallery section of the passdiy is no longer available for the moment, if you have build an Nelson Pass amplifier can you post pictures of it. It will help me and others to get inspiration for designing our amplifiers. I develop a kind of interest lately in looking for different amplifier aesthetic design and layout. It don't matter if your design is orthodox or unorthodox, just share your realization. No need for words, only pictures will be enough.

Thanks in advance

Compact amplifier recommendations

I am thinking about replacing our ancient CRT television to go for one of those new-fangled thin ones to hand on the wall. Noticing that the sound is pretty much crap on these I would have to buy a sound bar what would add to the cost. I can't see how something so skinny can be that good so I came up with an alternative idea.
I have a pair of very nice B&W bookshelf speakers (8ohm) that are never used now that I have finished building my Paul Carmody Tarkus floorstanders. All I need is a two channel amp to drive them and I could use this setup (plugged into the headphone socket) of the TV to get better sound. I'm not keen to spend a huge amount on an amplifier and have been looking at secondhand Sony amps online but they are not only silly expensive but I'm thinking something much more compact might make sense. A see lots of tiny amps from China but although they are cheap they usually don't come with a power supply and many are mono only so the price just goes up and up.

Any recommendations?

Amp Camp Amp - ACA

:Popworm: Looky Here... Original article by Nelson Pass:
Amp Camp Amp #1

Info for Amp Camp Kit (updated by Moderators)

Here's the ORIGINAL step by step photo build guide: ACA illustrated build guide

A new Build Guide for the V1.6 Two channel Chassis in the diyAudio Store.
Amp Camp Amp V1.6 Build Guide - diyAudio Guides

The small changes of the 1.8 version.All ACA’s that have 2 channels in one chassis can be converted to Version 1.8 which only requires buying a different rear panel switch and some re-wiring of the rear panel. Amp Camp Amp V1.8 Change Information - diyAudio Guides

The link below is to a Step by step build video by Patrick Norton on his TekThing website. He makes an error in cutting out the thermal insulator and leaving the backing on. Thebacking just peels off, no cutting required:
February 2016 Patreon Build Video: Amp Camp Amp Dual Monoblocks! - YouTube

See post #1453 for a tweak to the original V1.0 circuit boards. It’s not essential but should improve the sound. This tweak has been incorporated in subsequent versions (1b & 1.5, 1.6,1.8). if you have those circuit boards or kits it's already added to the board, and the part (R15) included in the kits

An ACA thread with lots of great ideas which may or may not improve the amp to your desires:
ACA amp with premium parts

Here’s a thread discussing the kits from the DiyAudio store for V1.6 and V1.8
Amp Camp Amp Kit 1.6/1.8

And here’s the link to the kits:

Firstwatt F1J

Nelson appears to have re-spun the original Firstwatt beast, designed as current amplifier, good for fullrange speakers. It got good reviews originally, but not often seen (IMO) as a diy project. I think it's worth discussing here.

The addition of the F1J with SiC JFet's replacing the IRFP240 output devices may breath new life into the circuit. A single stage amp I think as refered as 'the truth machine'.

Here is what Papa says.. (Paraphrased)
The F1J is an update to the F1 where the two gain Mosfet transistors have been replaced by new state-of-the-art power Jfet devices. In addition, there have been changes to several resistor values and removal of the input zener protection diodes.
You may notice that the F1J also has approximately 1.5 dB more gain. This is because the Jfets have a higher transconductance figure that the original Mosfets.

There is another factor as well, which is that the F1J has a lower input impedance than the F1- approximately 30 Kohm balanced and 15 Kohm single-ended. The modifications that help achieve this bandwidth take advantage of lower impedances, so the F1J is recommended for use with preamps with ordinary to low output resistance – tube preamps without cathode followers will work but will not reap as much benefit at high frequencies.

This caveat aside, the F1J delivers a dramatic improvement in current-source amplification. I have often ventured the opinion that improvements in measured performance in simple Class A circuits (particularly with no feedback) usually have the best correlation between what you measure and what you hear, and the F1J bears this out. I think it sounds about twice as good, and I feel certain that you will experience the same remarkable improvements.

Maybe Nelson will share some details for those with the amp, maybe not :p

Best high frequency Class D amplifier at 24V. Thoughts please?

Hello all,

I am looking for the best class D in high frequencies from 1Khz to 20Khz from a 24V supply.

Low THD and 25W (8R) on a single channel is all I need.

I have tried old Tripath, TAS and TPA series from TI. All sounded OK, but I have not been blown away. The implementations I have used are quite basic I think.

Can anyone make any suggestions? I want to keep it off the shelf as much as possible but I am happy to make small modifications if it is very beneficial. Cost I am looking for less than 60USD if possible - so no Hypex unfortunately.

Many thanks to all in advance for your thoughts.

A Study of DML's as a Full Range Speaker

Edit oct 27, 2021: a nice Google drive library of DML publications by vdljev:

DML - Google Drive

Edit April 1, 2020: nice summary of DML patents by Burntcoil

A Study of DML's as a Full Range Speaker

Edit Aug 12, 2019: Nice summary here by BurntCoil on how to maximize performance.

I had some cheap exciters that I got from PE a while back and tested them out a while ago with a full 20x30in FC panel here:

Foam Core Board Speaker Enclosures? - Page 225 - diyAudio

I found that a large 20in x 30in panel can sound quite good with nice bass extension and a snappy transient response:




Frequency Response & Harmonic Distortion:


Impulse Response:


The results were interesting in that it sounded nice - with surprising bass and good midrange. I thought nothing more about it until recently prodded by the master of DML, CLS. He has worked on this extensively and is a treasure trove of good info. I since have discovered that you can really do some cool things with them by playing with driver placement, cutouts, adding mass, adding felt, adding ribs, making them huge, making them multi-way FAST, etc. the options seemed almost limitless. Take for example, a large center channel and a super 40Hz capable multiway that CLS built here: PIEZO NXT type panel - Page 60 - diyAudio and PIEZO NXT type panel - Page 61 - diyAudio

I feel like this technology just isn't getting enough attention. There are several very large threads on this on the web. It might be tough for a newbie to comb through. I am a newbie at this so thought I would document my journey for the Full Range forum to follow. I think it really could be a great full range speaker with some careful experiments. This will be really useful with some modeling using CAD and FEA modal analysis - such as available in many CAD packages like SolidWorks. One can play with shapes, cutouts, mass loading, variation in thickness and materials, boundary clamping conditions, etc. The idea is to spread the modes evenly with not any one mode dominating and causing a spike.

First thing is to play with it to get a feel of what we are dealing with. What is nice is that it is relatively cheap to play with. Exciters cost $3 to $20 ea and can be made by removing or cutting out large holes in the cone from an old driver and leaving the spider and VC to attach to the panel. Foam core or corrugated cardboard doped with shellac or PVA seems to be the materials of choice.

Some interesting facts:

1. Although it has no baffle, it is not an open baffle (OB) dipole in behavior - that is, there is no huge bass rolloff and it hits surprisingly low (40 to 50Hz is easy) for a zero baffle driver.

2. It is not a dipole but behaves more like a bipole or an omni.

3. It has very quick snappy transient response - nice drum sounds.

4. It is sensitive to how you mount it or frame it or hold it.

5. You are building a driver in reality - a driver and zero enclosure.

6. You want to avoid symmetric shapes and symmetric exciter placement in order to reduce the effects of the main symmetric transverse drum head eignmodes. Think reflection anti-symmetric shapes like uneven trapezoids, pentagons, blobs, etc.

7. It operates more by having high velocities and large areas for good efficiency vs large displacements - thus small drivers and large panels can be surprisingly loud.

8. The impedance is essentially "flat" relative to normal drivers in that there are modal peaks (many of them) but they range from nominal Re value (say 6 ohms to maybe 8 or 9 ohms throughout the 40Hz to 20kHz range - this presents a very flat load to an amplifier.

Here is a photo of a basic panel I was testing (right before I cut off some edges to form a trapezoid) - panels is about 1 square ft in size and made of standard dollar store foam core board. I suspended it with two pieces of twine from the top corners between a ladder to reduce the effects of edge boundary clamping:


Then I started to play with mass loading by adding blobs of modeling clay (8, 5, 4, 2, 1, 0) so you can see the effect on the resonance modes and the harmonic distortion. What is neat with this test is you can do it live while playing music and immediately hear what sounds more pleasing to the ear. Note the 50Hz bass extension. It is also surprisingly efficient with 85dB and a puny little voice coil. These are 0.5m and 0.71v for equivalent SPL at 2.83v and 1m.

Frequency Response and Harmonic Distortion for...

No added mass:


8 pieces of added mass:


5 pieces of added mass:


4 pieces of added mass:


2 pieces of added mass:


1 piece of added mass:


Impulse Response of 1 piece of added mass, note the sharp transient capability with relatively low after pulse or ringing:


I liked the sound of the 5 and 1 mass the best and for a FAST with a 200Hz XO, the 5 mass might actually do fairly well. Of course, sound clips to follow once I have more time to work on this. Just to demonstrate how quick and easy this is, I did all these experiments in less than an hour including making the DML.


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JBL Studio 530’s as Synergy Donor

I recently got an pair of JBL Studio 530 monitors on sale for $250 direct from JBL. I was curious what an entry level horn loaded CD 2-way monitor could sound like. They actually sound quite decent and measure well when the tweeter is padded down a notch. The reviews of these are generally very good and for $250, no DIY project will come close really given the nice cabinet (no parallel walls in sight), a horn, passive XO, and decent bi-wire/bi-amp 5 way binding posts.

What intrigues me about these is that the horn has lots of opportunities for cutting slots and holes for mid range injection to make a bookshelf Synergy. Has anybody thought about doing something similar? My one reservation is that this speaker sounds very good as is and I would hate to cut into it.

Here it is next to my 10F/RS225 TL speaker for size comparison. It works well with either my Class AB or class D amps. It needs so e power though, probably at least 40w to really come alive.

This is how I padded the tweeter but adding a resistor between the woofer binding post and tweeter binding post.

Here is how it measures with the tweeter padding in place. Without it, the response is a bit bright for my taste. The JBL 530 is the yellow trace and the blue is a new speaker I just developed with a typical “Harman house curve” voicing for comparison.

Here is what is interesting, Ron from New Record Day, did a tear down and you can see the inside of the horn. Lots of open surface area for mounting small 3in midrange cones for a mid injection a la Synergy.

Anyhow, I thought I would just throw this idea out there to see if anyone else has wondered the same thing.

Here is the XO schematic from The manual:

Here is the horizontal directivity from the ASR review:


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Open source Waveguides for CNC & 3D printing!

I've been working on a waveguide project where I would develop high performance waveguides for some popular tweeters, and than share the files for anyone to print or CNC as they are able. The discussion started here: 3D printed waveguides - Techtalk Speaker Building, Audio, Video Discussion Forum for more details. The short summary is starting with the SB26ADC and a 5" waveguide, I varied flare radius, phase shields, depths, etc. I've started to find some best practices (at least with this dome/horn combo) and all future guides will have elliptical mouths, and with and without phase shields. I then skipped to 8" designs to verify those best practices scale, so anything in between should be trivial to design and still have the expected performance. Tweeters that I'm currently designing for are: SBA SB26ADC, SBA SB19ST, Satori TW29RN, and Transducer Labs N26C-A.

To get some frame of reference, here measurements of the Kef Reference 5 prototype, and Revel Concerta2 (which I suspect also uses the SB26ADC):



Here is my "C" waveguide with SB26ADC, with and without phase shield:



Quite good results I think, better than Revel achieved with the same tweeter! Anyway, the reason I am posting now though this project is still in its infancy, is I've connected with a couple gentleman with the ability to model waveguides. This could speed things up considerably, as waveguide design is extremely iterative otherwise because 90% of the performance happens at the dome/throat interface and this is not easily modeled.

We've started with verifying that the sim can accurately predict reality. With as close a representation as possible of the dome here are the results:



Extremely encouraging! I'd like to do some additional verification - particularly of the 8" guides I've started working on - and then I hope to push the sims to the max, and start producing some really excellent guides for popular tweeters.

My attempts at a design of a 3 stage amplifier

First, I will admit to myself that these attempts may prove useless.

After so much head scratching, I inputted the input stage of what I think the input stage should look like. I am using the CAD hog named KiCad. It is a huge piece of software that probably requires one to buy a book to even start using it. As you can see, I haven't figured out how I can neatly display the various texual descriptions displayed next to components.

The attachment is the first stage as I am imagining it. I will use a cascode to isolate the input from the high voltage of the power supply. I am aiming to first make the input stage, test it to make sure it meets its required standard and then proceed to the VAS. The power stage is already built as it was part of a large public address amplifier that failed. I will usethe PA amplifier's chassis, power supply and power stage and redesign the pre-driver stages.

You may deem me mad, but sometimes being mad may be the only adventurous and successful route.

I am posting both for your comments (criticism) and hints about how I can use KiCad to get a better looking schematic and for improvements that I can make to the input stage.

Thanks to all those who made this website a reality and to those who will contritbute to this thread.


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CD puzzle

I recently bought a 2-disc CD album. Popped them into my Sony multidisc carousel and find that one disc plays fine but the other is really dreadful. On first couple of attempts it just sort of "jitters". I tried it in different positions in the player and no difference. No scratches or visible damage at all. The seller claims that he tests all the CDs he sells on a PC before he posts them. I tried the dodgy disc on my desktop PC and sure enough, it plays without issue. I have about 350 CDs that play well on the Sony player but this is the first disc that doesn't work.

Why might this be? Manufacturing defect? Player laser out of alignment? Something else?
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