First a big thanks to Stephe for her videos/guides on this A50. There is much work involve making/editing those videos, great work!

I have always wondered about no feedback sound thru my audio journey. Started with Fisher 300/400, progressed to Dynaco, large tube mono blocks, threshold and parasound, most slightly or massively modified. I'd thought it was time to make an effort to sample a SET amplifier. Along comes the Boyuurange A50 mk3 300b. I have followed along Stephe's path, from initial purchase to the full modded version and would like to share my experience. Been doing the audio thing for a long time, almost 50 years. Of course, can't hear as well now. Maybe the reason I don't experience much break-in sensation of parts. However, I've have learned to listen carefully over those years.

My system is made up of sources; Meridian, Oppo modded for 2 channel only, VPI/Dynavector, Tara labs bi-wired Von Schweikert VR-5 HSE(91db). Multiple DIY interconnects (RCA/Eichmann) . Room has been tuned as best I can manage for a non symmetrical arrangement. It very difficult to explain sound as we all experience and prefer a certain presentation. I for one have had a long battle between detail/edgy, warm/blur with the soundstage definition a priority. I'm a low level listener, no 100db level here, and mostly acoustic/folk and light rock.

Stock A50;. I only listen long enough to make sure the unit operated. I only recall the sound was encouraging, and leaning toward my liking which I suppose is "musical", what ever that means to you and me.

Mod #1; As in the videos, I raised the voltages as Stephe advises. Jumper resistor, 5AR4, cap between the chokes, changed 6sn7s to 50s GEs. Now this was a very nice upgrade. I was using the 4 ohm taps to match the impedance of the woofer section of my speakers. The mid/tweeter section is reported to be 8ohms, for an overall 6.5ohm specified impedance. Wow, the ease of the presentation was a nice experience for me. Lacking bass NOT. I can't explain how or why, but musical without having to ramp up volume to get a full picture if you know what I mean. Not perfect, but very surprising, fine detail a little muted. My system, my preference, I could enjoy this for awhile, YMMV.

Cascode mod;. First I have Auricaps(.47 for coupling) and KZ Muse for the 300bs. The first obvious change is the input sensitivity dropping quite a bit. To achieve the same loudness the volume control must be advanced at least a quarter turn or more than previously. Not because loss of power output, just the loss of sensitivity. Overall a cleaner general presentation. Bass also diminished surprisingly but was better defined. The overall presentation had lost it's, say it, it's ease of presentation leaning towards SS. My opinion. What surprised me was the arrival of delicate detail. Can't think of a better explanation, just that. Little delicate details in voices and in the soundstage became apparent. Not forced into the presentation, just floating into the picture.

There is little run-in time on the mods at this time. I will give it an appropriate "break-in". I could be tempted to go back one mod to only raising the voltage. Will see....

I'm not clear if this is the right place to post this.

I designed and built a 2A3 amp.
6SL7 input tube in SRPP directly coupled (Loftin White) into 2A3 running about 50mA bias, AC heaters.

I have a hum in the right channel with no input connected that goes away once the volume pot (100K, Alps Blue Velvet) reaches about 1/3 volume. To clarify the noise is there from 0 -1/3 at constant volume then quickly fades out and it gone up to full volume.

My first assumption is this has to be a ground issue, but I'm unclear how that could be only on the right channel.
I'm at a bit of a loss as to where to start to try and track this down.
Everything is grounded through a busbar running down the center of the amp.

Any Suggestions

If this is not allowed, please delete.

I'm approaching 80 years and it is time to let go of some horded parts. To this end I've listed them on eBay. All are TO-3 cased power transistors. To see them just search on my eBay ID "jdfalconer"

Thanks

I'm working on an AMB headphone amplifier.
Pretty sure the opa627 opamps have failed.
These opamps are nla, at least in the quantities I need.

Can anyone suggest a drop in replacement ?
8 pin DIP package.
Ta.

Several years ago I investigated much time to understand the fundamental principles how to control the directivity of a loudspeaker. I made research using ABEC and some prototypes. The document was written in German so it was limited to a small number of readers compared to world's population. I now translated it to english so that anyone can read it. Please tell me if the translation has any mistakes or is hard to understand.

I hope the document may be helpful. 🙂

Manipulating Directivity

Hi, this is going to be an extreme noob question. I purchased a pair of used/pre built speakers (Jeff Bagby's Solstice, Parts Express) from a person who shipped them to me a few months ago. Unfortunately they seemed to have suffered some damages on the way here, and I'm trying to fix the issues. I'm new to this, and only built one pair before myself that turned out without issues so I'm very lost trying to find the root of the issues.

The tweeter of one isn't playing, and the mid/bass pair of the other isn't playing. The crossover is built on a PCB, and the wires going from input - crossover board - drivers seems ok, I reattached them. There's still no sound from the tweeter, and woofers on the other.

I just bought a multimeter, and I would love to learn how to find the issues. Is it the PCB? Are the drivers damaged? Is there a weak connection somewhere?

How do I begin?

Really appreciate any help here, thanks!

Please post your driver choices, alignment and thoughts each in one post. Crossover components don’t need to be listed but please post your budget for components. Box build and hardware are not included. Thanks for participating!

Im going to pick up a Cambridge Audio azur 650a in next couple of days.
I would like to mod it and upgrade some of the components.
A comprehensive swap of electrolytics will be 1st thing, starting with C24,25,26,27 c41,42,43,44 currently 8 at 2200uf 50v , scene on a vid somewhere guy replacing caps on a CA A1 and here reduced the number of caps by half, so instead you end up with 4 caps of 4700uf 50v.
I was of the impression that you could up the voltage also?

Has anyone on here modded a azur 650a? or similar?

Suggestions on a postcard

Ta
Paul B

I just bought a Tivoli Pal radio from ebay.
The problem with this radio is that it can not charge it's internal battery . I checked the battery pack on the back of the unit and did not see any obvious problems. The unit supplies 14.8-15 volts of DC voltage to the battery pack for charging. But the batteries do not charge!

I took a closer look at the battery pack and noticed that something like a big resistor is connected in series between two batteries (of the six). This component has two legs and a metal body for cooling I suspect. It writes KC100oC 250V 5A. Does anyone know what this is? Maybe this is causing the problem. Can I bypass it?

Many thanks
George

Hello,

I have a Hagerman Clarinet preamp which is missing one of these metal clips and the corresponding countersunk screw. The clips goes on the chassis, the top panel goes on, a countersunk screw attaches the top panel to chassis via this clip. I'm thinking of selling the preamp and would like to have it all together before I send it off to someone else. Any tips on identifying/acquiring this part would be appreciated.

The chassis is from Lansing, I've reached out to them but yet to hear back.

Cheers,
-Art

I recently picked up a carver pm 1.5 and it has speaker protection dials? On the front panel that I don’t see in the mainstream pictures when searching for how to set them. I have only seen two other pictures but they aren’t referenced at all. Can anyone give me any information on these? They are labeled rms output voltage and can set set by a flat head screw driver for delays of 1.5 and 30 seconds. Attaching a picture.
thanks in advance for any help

Hi folks-

I bet many of us have systems with a crossover frequency right smack dab in the Schroeder region. Let's chew on that specific problem. Do rules of thumb exist?

Crossover slopes is my main question - do we like a particular "taper" or "feathering" from ray behavior to wave behavior?

I'm thinking more about how you slope the woofers than the mains. I think the mains lowpass is dictated by your power bandwidth needs, and you typically take all the lo end you can get.

On the other hand, you can noodle the subwoofer highpass all day and call it art. But what do the great artists do?

Put another way: Assuming ideal speakers & ideal subs but non-ideal (real) rooms, does an optimum Schroeder transition philosophy reveal itself? Thanks.

Updated December 2023

Kubelik NOS DAC kits have now reached the end of their almost 2 1/2 year lifespan and are no longer available. If you'd like a more recent design, have a look at Dorati - https://www.diyaudio.com/community/threads/dorati-nos-dac-kits.387035/ and Abbado II - https://www.diyaudio.com/community/threads/abbado-ii-nos-dac-kits.400326/

Toscanini https://www.diyaudio.com/community/threads/toscanini-nos-dac.389937/ is an enhancement of Kubelik with gerbers, Mouser BoM and schematic freely downloadable but no complete kits.

------------------------------------------------------------------------------------------------------------------------
PM me and be sure to include your payment method and location so I can quote you inclusive of fees and shipping. Kubelik is an upgrade of 'PhiDAC' and keeps the same physical footprint of 81mm * 50mm, the maximum height is 19mm. The design is non-oversampling (i.e. no digital filter on-board) and the input format is I2S (three signal wire) at 44k1/16bits. BCK can be 1.4 or 2.8MHz, no MCK is required. Output is CD standard 2VRMS. There's a digital invert function which allows a balanced output DAC to be made from a pair of Kubeliks. Schematic may be found here : lingDAC - cost effective RBCD multibit DAC design

Preferred payment method is via Wise which typically adds a 2% fee. Our receiving currency is CNY, alternatively USD or Euro. PayPal may also be used, in USD but will attract higher fees, about 16%.

Price for a Kubelik kit : 128RMB (~$17.60)

Shipping is in addition and depends on your location and speed of service. Courier (FedEx, TNT, DHL) typically takes 8 - 10 days and e-packet four to eight weeks. Not all locations can be serviced by e-packet though.

FAQs

What else is needed to turn the built up kit into a fully operational DAC?

First you'll need a well regulated low noise power supply of 20V rated at 100mA or higher. An LM317-based board set to the correct voltage will suffice if you already have an unregulated supply (like a typical wall-wart). I don't recommend switching supplies due to issues with common-mode noise, its very hard to filter out. We can supply an LM317-based board with either DC (for unregulated DC) or AC (for a transformer) input option.

Second you may need a digital interface card. I say 'may' because some digital sources produce I2S directly (like Raspberry Pi, dedicated SDcard players) but most sources will either output USB (like a PC or laptop) or S/PDIF coax (a CD or DVD player) or Toslink. We can supply a card for interfacing one (or more) of those sources to Kubelik's I2S input. A CM6631A-based card for USB input is the premium choice as it operates under 'async USB' which is the lowest jitter. A mid-range alternative is an interface based on an STM32F4 microcontroller - while still low jitter, its output is not as clean on start/stopping as with CM6631A. In the bargain basement dept are the interfaces based on 'adaptive USB' such as CM108 and PCM270X. The S/PDIF board we recommend handles both coax (two inputs) and Toslink. Further, it has a switched I2S input - this can accept I2S from the USB source. A single pole switch acts as source selector, cycling through the inputs. An OLED screen is an option to indicate the selected input. The one drawback with this board is it needs a 5-12V supply, so a pre-regulator is necessary if fed from the DAC's supply. The simple coax/Toslink board needs a regulated 5V PSU.

Third you'll be wanting some output sockets, typically RCAs so you can connect your finished DAC to your amp or preamp. We can supply these and we're working on a PCB to mount them to make outputting Kubelik to your system easier.

Lastly, and this is obviously optional for a DIYer, is a case. We haven't supplied cases in the past because they're so heavy (i.e. expensive to ship).

USB CM6631A card examples : https://www.aliexpress.com/item/32874113831.htmlwww.aliexpress.com/item/1005004083748180.html
USB STM32 card example : https://www.aliexpress.com/item/1005003632369097.html
USB PCM270X card example : https://www.aliexpress.com/item/4000141799137.html
Multi-input S/PDIF card : https://www.aliexpress.com/item/1005002923079600.html
Coax/Toslink S/PDIF card : https://www.aliexpress.com/item/1005002772984954.html

Do I need special tools to build and test my Kubelik kit?

You'll need some fine diameter solder (0.3mm is recommended), a temperature controlled soldering iron with a fine bit and a pair of tweezers. A magnifier comes in very handy but that depends on your eyesight. Desoldering braid is helpful for correcting mistakes. If you've never soldered SMD before then maybe Kubelik will be too challenging for a first project as there are more than a hundred parts. However none of them are microscopic (the smallest is 0805) and none of the ICs has pins closer together than 1.27mm. For testing you'll need a DMM (digital multimeter).


What's supplied in the kit?

There's a picture directly below of the contents : the bare PCB plus all the components that mount on it (resistors, caps, inductors, LED, ICs etc.). Given that 0805 sized components are incredibly easy to lose, we include a spare or two for each value. Input, output and power are supplied via 4pin Molex-style headers, we supply the mating half with crimped wires to these too.


What, if anything, is unique about Kubelik's design?

Commercial NOS DACs typically have minimal filtering after the DAC chip itself. Kubelik has two kinds of filters resulting in a 5th order overall lowpass response - a 3rd order passive filter prior to I/V and a 2nd order active filter afterwards. The passive filter prior to any active stage improves subjective dynamics - it means the I/V opamp no longer 'sees' a step waveform out of the DAC chip, rather a continuous signal. The active filter provides 'NOS droop' compensation - meaning you get a flat frequency response to around 17kHz whereas a typical (not every) NOS DAC has roll-off approaching 3dB by 20kHz. It also has headroom to cope with 'intersample overs' which may occur on some heavily compressed recordings. Meaning it won't clip its output no matter what digital input you give it. Opamps are used but their outputs are buffered with discrete transistors as I've found this results in improved instrumental separation when the music gets very 'busy'. Kubelik's DAC chips are 'multibit' but they're not strictly speaking 'R2R' as internally they use no resistors. Instead capacitors are used as elements in the DAC which have their charge constantly refreshed (similar to the DRAM in your computer) to compensate for any drift.


Here's the build and test guide for Kubelik - lingDAC - cost effective RBCD multibit DAC design

Update : The two older versions of the stuffing guide had various errors, here is the up to date version : https://www.diyaudio.com/community/...-rbcd-multibit-dac-design.324933/post-6889095

Thought that it might be useful to have this as a container for things cartridge related. To start off here is a link to Part 1 of a post by Michael Fremer re. cartridge azimuth.

In regards to measuring azimuth I mentioned a little box that Bob Graham markets which I believe takes the left/right channel sums them while inverting 1 channel. Then by playing a mono recording, without a lot of high frequency content, you can adjust azimuth till you get maximum cancellation. Please someone chime in if I got this wrong.

What is the solution to this problem without adding a whole lot of complexity to the power supply?

1) I want to replace the Russian 5Ц4С with solid state rectification in this power supply, and I don't want to jack up the voltage. The voltage drop across the rectifier tube is about 45 volts, correct? How do I get rid of the excess voltage from solid state rectification without harming the power supply performance and preferably improving it? If I can use solid state and get a performance improvement at the same time, great!

2) I also need to drop a little more voltage because the transformer is rated for 110V and I have 120V from the wall. It's a single-ended, 6H8C - EL34 amplifier, and I don't know what the current draw for that might be. The choke is rated at 200mA. Specifications call for 310V and 285V out as shown. Wall voltage is 120VAC going into a transformer designed for 110VAC.

3) If I decide to use tube rectification, what is the expected lifespan in hours for a longer life replacement tube, and which tube type to use? 5Ц4С is rated only 500 hours. I really want the convenience of solid state like my other three tube amps. Only 500 hours is a real pain, and the cost adds up as I put a lot of hours on my system.

I can make simple changes, as the amplifier hasn't been built yet, but I do not want to add a whole lot of complexity to this schematic. There has to be some reasonable solution.

Let's not discuss the merits of or problems with the audio circuit here please. Let's save that for later if I build this kit. Let's focus on the power supply as that is all that matters right now. Power supply design is a subject of its own and a critical skill, so that's why I started this thread.

Dateline: Late 70's. My first job in broadcast, a 3KW FM/5KW AM radio station.

The station was built on farmland but the suburbs had grown to surround it. One day I got a call from a very upset but very sweet and very old woman. She was mad that she couldn't NOT hear our station. She had a lot to say so I heard her out, and it turned out she was convinced her toaster was possessed because it was speaking to her.

She lived at the back corner of our property. I had to go see for myself.

The AM station was a four tower array with different daytime / nighttime patterns. Both patterns had a lobe pointed straight through her house. The closest tower to her was all of three hundred feet away.

I was met with the specter of a vintage chrome toaster singing Cher's "Gypsies, Tramps and Thieves", clearly and unambiguously, directly to me. It. Was. Haunting. The lady was right!

Now I don't know if Satan exists or not but I was damn sure he wasn't gonna use my radio station as his unholy vessel. And I can't speak for Cher's relationship with the evil one but I suspect she was an innocent in all of this. Then the toaster told me the weather.

I was fresh out of garlic and crucifixes so I did some LC thing on the powerline and cleansed all the souls involved. Sadly it was before the movie Poltergeist so I didn't think to say "this house is clean".

Hello,

Was hoping someone could help me figure out what might be the problem.

I have a Marantz pm6005 that I have stopped using because the right channel would produce no sound or almost no sound. Sometimes if I turned the volume all the way up I could barely hear it. I swapped the speaker cables, tried different sources (digital/analog), different speaker outputs (A,B), cleaned the volume pot, and also replaced the volume pot.

But the problem persisted. Sometimes it would work for a few hours or days then randomly it would stop.

About 1.5 years ago I took it to a repair shop and they kept it for 3 weeks to see if they could reproduce the problem and, according to them, it never happened while they had it. I picked it up and that same day the problem popped up in my system. At this point I gave up on it and started to use a different amp.

I have some time now to really look at it again and would like to be able to locate the problem and fix it if possible, however I'm not sure how to approach this.

Any help would be appreciated.

Regards,
R

Full size MAME Arcade cabinet build, that will also double as playing blu-ray movies. Started with intent to repurpose very old auto components/amp, but I need to pivot to using full range, and a much more efficient amplifier/speakers. I do not want to have a powered sub, so will probably need at least a 4-5 inch speaker. Will also likely be powered by a not yet acquired simple 2-channel amp board, like the Dayton KAB-250v4 2 X 50W

Any suggestions on a good full range that would have a decent amount of bass? I have been out of the building game for some years now, and never really tried full range designs before. I will be putting a new baffle panel, so will not need to use existing. I also would not be averse to constructing a sealed enclosure behine the baffle for each driver, if that turns out to be necessary to get proper bass response.

I know the HiVi B4N's could be an option, but haven't any experience with using them full range, without a tweeter.

Hi All,
Please listen to the recorded mp3 file : I play a pure sine wave (852Hz) . As I turn the level up, an strange noise apears. I have no clue where the problem is. My monitor is SC307 which uses SMPS , DSP and Class D amplification. Any help would be appreciated

HEC amplifier topology created by Bob Cordell. I'm interested to make simulation using this topology.
It used 24VDC PSU and OITPC compensation that created by Dadod.
Output stage is simple using double emitter follower with driver bootstrapped. Using small transistor in driver,
make loop gain higher because their high hFE.

Any suggestion are welcome.

Hi I need a replacement
Sp1587 driver for KEF q500

Attaching pics of amplifier chip number

If someone have any info regarding the wattage let me know thanks

I came across an issue where a spice model isn't made for a part (the one in question is the TPA3255). I'm not really trying to do any distortion measurements as much as just checking for signal integrity from input to power stage. Is there a way to simulate a chip amp like that using the universal op amps? If not, is there a way simulate the power uplift from the output stage? (I was also considering just doing a simple transistor class A or something just to complete the simulation, but I figured I would ask just in case)

The hard dome says "When I'm surrounded by a waveguide, I am smooth and can control my directivity"


Reference:
SB26CDC in custom 6" WG by @augerpro



The ribbon tweeter says:
"Really? I don't need a waveguide to be smooth or to control directivity. And I can be heard from all around"



Reference: Fountek Neo CD3.0 datasheet


The compression drivers says "Well I may not be as smooth, or play as widely as you two, but I'm far more dynamic"


Reference:
Tymphany DFM-2335R00-08 in SB Audience H225 90°H x 70°V constant directivity horn.



The soft dome says "Well I may be a bit rough around the edges, and I'm not as sensitive, but people have accepted me just the way I am"








Reference: SB Acoustics SB29SDAC centred on a 8" wide x 12" high baffle

edit: correct SPL responses for 2.83V @1m, clickable polar maps for comparisons, example HF units explicitly named

I am planning to build and LCLC PSU filter for a tube PSE amplifier, and I am debated on 'how good' capacitors I should use in each position to achieve the best sonic performance.

My though process:

C2 is connected directly to the anodes, so the current across it is characterized by large/steep swings and the same frequency of the audio signal, hence I want a high performance capacitor in that position: most likely a high grade electrolytic capacitor in parallel to a film one.

On the other end, C1 current swing frequency is limited by L1/L2, hence my deduction is that any decent capacitor should be good in that position.



Any opinions?

hi.
i am looking for these toshibas and the KSA.

also maybe someone can provide FQP3P20 and FQP3N30 instead of toshibas?

primary i would need a matched quad of thoshibas.
secondary i take also 2 octets of the FQP‘s instead if toshibas are no option…

i appreciate the help of the pros here.

regrads from vienne

Hello,

This is my first topic in this forum, my name is Jan, I live in Germany and I'm interested in audio circuits building mostly Headphone and Phono Preamps the last years. I often use tubes, my goal here is to use technology from 70 Years ago and build something that performs on a level close to modern circuits.

My last project was an Phono preamp using INA849 instrumentation amps in the input, ECC83/12AX7 tubes for the LF equalization and OPA output stage. The circuit around the ECC83 was “classic”, a feedback loop was limiting the gain to 10dB in the HF range, at 20Hz the Gain was 30dB. The highest harmonics (K2) with 1.55V output was around -85dB, measured with an AP ATS-2. Not bad for tubes.

I recently found a real treasure, 2x EF12 NOS Tubes that have been build by Telefunken before WWII. I really think about using them in a phono hybrid circuit again using OPAs in the input Stage (AD797 instrumentation amp) and do all the equalization in a circuit around the EF12 where noise is not an issue. They will be in a shielded case because unfortunately the cathode is connected to the shielding of the tube which is basically an antenna.

My goal was to improve the performance of the ECC83/12AX7 circuit. The output of my old circuit is limited to around 5V, after that THD is increasing. Typically for such an circuit, THD is rising with higher output levels.

So I was simulating OPA circuits, really good results I got with the HDAM design. (HV+ = 150V, V+/- = +-24V) To my surprise, using tubes and transistors in the differential amps is not really an issue. Sure, the offset is extreme because of the unbalance in the input stage, many Volts. But with capacitor coupling (an using caps in the feadback loop deceasing gain to 1 at DC) this is not really an issue. To my surprise in the simulation this circuit reaches around -96dB distortion (mostly K2) @ 5V output in 1kOhm. Using 2 tubes in the diff. Amp does not really improve things here, THD is around the same. I'm not sure how this will perform in real life, the tube could be better in the simulation than in real life. For sure this circuit has some problems, if you power the circuit, output will rise close to the V+ rail until the tube is heated. Stability is really good, circuit is unity gain stable with phase margin > 60°



Would like to hear your opinion! My feeling tells me I will get trouble because of the Tube/Transistor combination in the diff. Amp, I was surprised how good this is working in the simulation.

Thanks!


Best regards,
Jan

Good evening, I want to make my first contribution since a lot of information has been obtained from this forum that has helped me repair some equipment.
Regarding the topic about the mosfets with their numbering erased, I have found a xion brand amplifier with the code A4 and the curious thing about this one is that they did not completely erase the surface of the mosfet, leaving a small detail that I now put in photos
When I dedicated myself to researching on the Internet, I found a page and brand of the possible company that manufactures the type of mosfet. I cannot guarantee that it is the only company, but when reviewing the stock, some values agree or are close to those most used by common brands of the same. form attached page link and make your comparisons I hope the info helps and does not affect anyone

https://wxdh-semi.en.made-in-china....nt-Mode-Power-Mosfet-DSG059n15na-to-220c.html

Although at the moment it would be impossible for anyone other than a company to acquire these spare parts, at least there is data to use and compare with those of other brands and look for a possible substitute.

sorry, I used google translator

https://www.ytaudio.com.hk/brands/product/204/

• 3rd generation twin-Ribbon technology
• Excellent vertical and horizontal pointing characteristics
• Parallel multi-wiring OFC transformer
• Improvement horn dispersion aluminum front plate
• Highly concentrate magnetic field neodymium magnet system
• High power handling

Lightly used, Asking 450USD include posting. n Paypal Fee

I did a bunch of experiments with crossfeed headphone stereo perception, using Chord Hugo crossfeed function, foobar2000 Meier crossfeed plug-in, and more recently a classic crossfeed circuit (Linkwitz-Chu Moy). I was able to achieve stereo sound, depth perception with singer/musicians/stage in front of me, albeit smaller and nearer than the presentation through stereo loudspeakers. The music separates/delineates more easily and sounds more natural. This effect requires:

(1) twisting the headphone pads "OPEN-WING" so sound comes from FRONT-LEFT/RIGHT (and very slightly above if possible), not shooting straight into ear canal; headphones with 2-degrees-of-freedom work best
(2) EQ DOWN both trebble and bass for a realistic sense of distance, but compensate for bass-loss due to pads not being sealed (try hand-cupping ears or draping flaps over the gap as in picture)
(3) time-delayed crossfeed to opposite channel (I conjecture that additional lower bass delay would be better)

Headphone Stereo Test Prep Music uploaded to China's bilibili (click triangle to play)
LISTEN WITH HEADPHONES "OPEN-WING" foobar2000 Meier Crossfeed set to max, EQ'ed https://www.bilibili.com/audio/am33118121?type=7
original/control for comparison purpose only https://www.bilibili.com/audio/am33116224?type=7

I hope there is interest in this topic. I have found a few circuit diagrams. Crossfeed miniDSP anyone?

I saw a video of NWAS 2018 where Scott uses an Spreadsheet to estimate the final response of the speaker in the room depending on position.

I have a pair of Mark audio CHN 110 and I would like to use this spreadsheet to estimate the response of the many speakers projects in the mark audio website to see what fits the best in my room

Somebody know where I can find this spreadsheet?

Link of the video in the moment Scott is talking about the spreadsheet:

Login to view embedded media

Thank you

Hello folks, I got this amp and someone had messed with it before. Looks like they tore off a transistor and I cannot find a service manual to tell me what it was. Can someone help me make maybe an educated guess? It is the one circled on the left of the first photo. I am guessing it is the PNP version of the CR533 such as a 2SAR533D but not sure. Is it possible it is another NPN like the CR533?

Hello folks, I got this amp and someone had messed with it before. Looks like they tore off a transistor and I cannot find a service manual to tell me what it was. Can someone help me make maybe an educated guess? It is the one circled on the left of the first photo. I am guessing it is the PNP version of the CR533 such as a 2SCAR533D but not sure. Is it possible it is another NPN like the CR533?

Greetings friends. I've found myself at the early stages of planning a DIY audio community and have been tasked with finding a suitable amplifier for a DIY kit to be assembled by newbies, and I am here to ask your advice.

I am looking for a PCB-based circuit for a power amplifier, an AB1 Push-Pull amp using EL34/6L6 output tubes and something other than those hard-to-find 7199 to drive em. I would prefer a cathode-biased circuit for simplicity, but will accept arguments for fixed bias design. Above all, I am looking for a DIY project with a high rate of success, so we can bring more people into the glorious world of Tubes.

Any ideas, projects, advice, or warnings welcome.
Thanks!

Will

I purchased 2 sets of these boards in October, populated and used them for about a month until I completed my own custom soft start control board. Purchased and built 2 sets as I have a pair of Aleph J's in bi-amp mode. They are ready to use!
Great price: $60 a pair (1 soft start, 1 speaker protect). Once you let me know your location, I will provide ship cost. I don't charge any extra on shipping, just recovery of cost!

Hi,
I recently acquired from a relative these two old tubes. searching the internet they look very similar to Western Electric 284D or alternative Amperex 211 VT4C?

Is there any experts who can identify these from internal construction. Photos attached

Thanks!

Not seen any posts from PRR since March.
Anybody know anything?

As a follow-up to a recent post: is it possible to apply a VBE multiplier with a Si transistor for a complementairy output stage with Ge transistors?
(See example).
R2 in the circuit must be of a very low value to avoid a melt down of the Ge's. But is it 'controllable' with a certain adjustable value of R1?
Wrapping up: what would be the lowest possible multiplied Si-Vbe?

Answers not needed:

• how Vbe multipliers work (explanations, doubts of my knowledge about this topic)
• to have things thermally connected / frequency related issues / driving or loading issues
• &c

Just: if, how, what can, what not. Nothing else.
It's theoretical.
Practical solutions from the past are appreciated, as long as they fit the scope.

Thanks Andersonix for your very single example.

Hi Sony VFET experts , I need help determing the rank of 3 vintage Sony VFETs found inside a part unit of a high end vintage Sony VFET amp the VFET is shown in the pic, your kind help will be greatly appreciated ! Thanks! And a very happy new year!🙂 the 3 VFETs are all marked SONY 2SK60 A580, I could not find any info as to what rank they might be .

By trying to detect why a Philips GM6012 millivolt meter does not work, I have to dismantle all the shields on the outside.
Does anybody know how I can do that? At this moment I only could detached the backside of the GM6012.
youtube did not gave me any hints.

Hello fellow DIYers !

With much help from the fine folks here I begin to master the design intricacies of my vintage integrated amp's MM/MC phono stage. The amp is 30+ years old and the only schematics I could find online were for the revision 3 of the design, whereas my unit is rev. 1. When trying to match the PCB to the schematic there were areas I couldn't make heads or tails, and it turns out there's a major difference on the implementation of the output stages.

Rev 1 implements a cascode stage while Rev. 3 doesn't; of course in both cases the output (TP13) is still taken off the center of the push-pull stage. See below.

Rev 1:


Rev. 3:


So my question is, why use a cascode at all if the output is not taken off the top transistor's collector? The top collectors are directly connected to the supply so there can't be any output taken there. My guess is to mitigate power dissipation in the output devices since the supply voltages are relatively high (The phono stage shares the same regulated voltage as the power amp section). But if it is for this reason, why drop it in Rev. 3, since that version has the same supply voltages? Simply to save a few transistors I guess... Or are there other advantages I don't understand? A cascode provides extra input to output isolation, but only if the output is taken off the top collector right?

Note that the second stage's output has the same cascode arrangement but with extra filtering capacitors between ground and base of the top transistors :



Thanks in advance for any insights, and let me wish you all the best for 2024, good health and successful projects!
- Joris

I have always been fascinated by magic tricks, some I can explain but some are a complete mystery.



From the 70’s onward, I played keyboards in the north of England working men's clubs, providing musical backing to all manner of variety acts.



On this particular evening I was at a club in Castleford, and the artist was Johnny Burnette, A one legged, close up magician I had worked with on many occasions.



I arrived at the club to find Johnny showing a magic trick involving a pound coin, to Alan, the drummer. I was at the opposite end of the dressing room (about 20 feet long), getting changed. After about five minutes of magic, Johnny announced it was probably time to get ready for the show.



Where is my pound coin, asked Alan. Oh, I seem to have lost it, said Johnny. He looked at me and enquired what time it was? I slid back my dress shirt sleeve to look at my watch, TO FIND A POUND COIN SLIPPED UNDER MY WATCH.



HOW? He was never within 20 feet of me. A one legged guy cannot spring across the room. Not hypnotism, I have worked with many hypnotists, and it has no effect on me.





To this day, I am still mystified.

Hi, I want to make a relatively compact speaker to listen to music around my apartment. I plan on using two drivers, one on each side of the front of the speaker.
What would be a good, full-range driver for this?

Hi friends,

Couple of weeks ago I bought this nice looking TB drivers.
My plan is to put them into a simple BR cabinet.
I Also like to reuse my old Stands that I kept from an old project.

Here 11,5 ltr Net.
Poort tuning 55Hz.

Anyone experience with this driver?

Hereby the first concept.

Hi all,

After several years of successful R&D for our loudspeaker company (A for Ara), we have a rather large haul of drivers we didn't end up using in production models.

I'd like to pass these along to the fine folks of this community.

Does anyone want to come visit and take the entire lot away for a very reasonable price? We are located in upstate New York (2.5 hrs from NYC and Boston).

Please reply here or email me directly: db@aforara.com

I'll work on a more exact list of what's on hand. Everything is neatly stored in boxes.

Someone with a bit of patience could easily purchase this as a lot and make a couple grand piecing it out for sale.

OK!
Rob

Turntables: VPI Classic 30th anniversary model, Collins, more (no Garrards, sorry!)

Here's a partial list of the drivers:

Hello folks!

I've scavenged a working power transformer, output transformer and speaker from a very dead Philco 1224 Gramophone, and my plan is to build a small guitar amp using those as the core. This is my first attempt at design, so I've cobbled together a best-guess schematic which reinvents as little as possible. In that spirit, the rectifier, filtering and output sections have been lifted straight from the original schematic:



For the preamp, I've settled on a single-jack version of the typical Fender input, cascading a couple of 7F7 tubes, and thrown in the most copied tone stack of all time for good measure. This is what I have so far - I struggled to find appropriate symbols for all the necessary components, so please excuse the obvious substitutions:



The matching BOM:



I want to start working on the component layout, but I suspect there are errors aplenty in the schematic due to my inexperience. I'm hoping that some more experienced people are able to look at my work and suggest improvements to the general topology and/or component values before I go further. Is there anything glaringly obvious about what I've got so far which you would do differently?

As I progress through the build, I'm also putting the source files up on Github too: https://github.com/akhumphrey/1224-amplifier

Hi all. First time poster here so if I have this is the wrong section please accept my apologies.

I'm not a DIY electronics person but I do enjoy dabbling in simple projects from time to time. That said I found a Logitech Z-5300 system at a local thrift store. It had all 5 satellite speakers and the control pod so I grabbed it up figuring I might be able to find just the sub on Ebay. Well I couldn't find the sub/amp combo for a decent (cheap!) price but I did find a working Z-5300 amp without the sub. I paired it up with a sub I already have and stole the 120v transformer from another cheap Logitech sub found at the thrift store.

Now as I am trying to hook things up I'm unsure of the proper connection to the transformer. As Wendle states in the thread linked below there are three sets of wires coming out of the Z-5300 amp. Two speaker wires for the sub, 2 power mains that go to the transformer, and 3 wires that go to the other side of the transformer. (These would be the longer green, blue and black twisted set in the photo Wendle posted.)

The problem is that my transformer only has 2 wires for the secondary side of the transformer, not three like what is coming off the amp. So I'm unsure of how to wire these up.

Do I just connect one of them to a single wire on the transformer and then connect the remaining two wires to the remaining single wire on the transformer? It's probably a pretty simple thing, but I'm very much a novice at the electronic side of DIY projects, so any help would be greatly appreciated.

Thanks!

http://www.diyaudio.com/forums/chip-amps/135930-logitech-z-5300-without-remote.html

Hello together, I am selling 2 KEF SP1587 (coax from Q100) including cover ring. Technically the drivers are very good, see impedance measurement (impedance measurement was redone especially for the sale) and visually they are very good. They were only in use for about 1 year and have been in the cupboard since then. Price will be 200,00 Euro alltogether but is negotiable. Shipment inside EU will be extra 16,00 Euro. Best Regards Johannes

Normally with phono amps a regulated or choke filtered B+ is advised but here is a what if.

Let's say one uses a decent RC filtered supply and uses a plate choke load on the first stage. In theory the first stage noise contribution is the most critical and high gain is desired there. Of course an active load would be another reasonable option I think.

Would the PSRR and increased gain be sufficient? Something on this order. R load used on second stage to allow DC couple to CF.

Unfortunately I know only this brand, which have realized this approach to obtain a lowest value of parasitic noise/sonic radiation (still an unwanted effect owing the use of usual MDF pressboards instead sandwich parts for chamber cabinet resp. box enclosure). - go also to
https://stereonomono.blogspot.com/2022/11/roksan-darius-loudspeakers.html
for further information.
Are there also other brands with this kind of fixing the speaker envelope ??

Also the kind of tweeter mounting with springs is of interest (never seen before and thereafter at other manufacturers).

Thank you for advices.

P.S. - for your information:
Also very special was the outdoor unit for the crossover network.
This loudspeaker was equipped with custom made transducers based on follow good known drivers:
1) KEF B200
http://www.zenn.com.sg/Marketplace ima…ch/KEF_B200.JPG
TL Links
2) Seas (similar to K26FX, but only single magnet, supronyl-cone+Ferrofluid)
either
http://www.seas.no/images/stories/vintag…h297_25tnft.pdf
or
http://www.seas.no/images/stories/vintag…h253_1_dome.pdf

Update on a post further down....... now trying to decide between teh Anarchy 7 and the Wavecor SW182BD03/4, or the Dayton Epique 7"

I'm designing a subwoofer for my specific scenario... Several drivers seem to fit the parameters I need.....and model a very similar frequency response in a similar ported box, etc. Trying to figure out if there's something else I should look for/think about before choosing between drivers.

I'm looking for a subwoofer that is...more "musical" and not about punch/shaking the house..... and won't be played at an extreme volume ever (I have downstairs neighbors that I don't want to constantly offend).... I just want to round out the frequency response in my room, more bass than the Carmody S2000 kit will provide. I'd like good low frequency extension, but at relatively low volumes, and I have box size limitations. (SAF, etc)..

Is there something else I should pay attention to that WinISD modeling wouldn't show when choosing between drivers?
For example, I'm looking at the Dayton 6.5" paper cone sub, or the Anarchy 7 aluminum cone sub, and other similar size sub drivers, like the Dayton Epiques, etc..... Is there some other parameter to pay attention to, like cone material? Or magnet size, basket, etc? Or will WinISD lead me astray? (Modeled 40hz performance of one driver vs another won't be accurate, etc?)

Thanks for your thoughts!

-Nate

So I’m planning on building a system along these lines for the horn section but instead replacing the 14” woofer with a pair of 8” drivers for an overall narrow presentation. Trying to figure out what JBL did here with the horn…..is it just an existing biradial modded and turned on its side?……JBL says 60 degrees horizontal in their literature but looking at the lens, how’s that possible?

Anyone have any data or points to share?…..I know there’s a member here who has them and I’ve auditioned them a while ago and remember them being really dynamic and engaging

Hello,
I need a switch Support or Bezel that allows the switches to be recessed inside of the case, here are photos of that part:



This type of Switch Support/Bezel was use in all the Nagra IV line of models but also in equipment of other brands,
here is a photo of some DI Box supposedly made by Helios (closed down in 1979) that used the same type of assembly:





Does anyone know any info on these parts?
Sources for it?
Or any other equipment that might have used them?

Thank you so much for your help

I’m pleased with the big reduction in hum level by removing the original built-in transformer and bridge rectifier and then using a toroidal transformer with an Ebay Chinese rectifier/capacitor board. It required a bigger box too. Hum level is so low as to be inaudible now even though I have increased the overall gain to give an output similar to CD. I also changed the original mica cartridge load cap with a polystyrene one and added a second switchable one to sum to it if required on each channel. Also, this circuit needed DC blocking caps on the output which at best is around 100mV...this value does vary quite a bit with different samples of LM4562. I have also included a series and discharge resistor on each side of the O/P caps as seems to be the norm. Sound quality really is superb and totally transparent using my Ortorfon VMS 30 Mk2 (fine-line stylus). The transformerless late board is now available shown below

Hello to all. Having built several rather sophisticated horn-loaded systems, I've recently heard the Voigt Pipe speakers. Yes, I saw that video, too. And now my hands are itching again. And this time, you guessed it right - I would like to build the Voigt Pipe. In order to overcome the inherent weakness of full-range speakers when it comes to very dynamic passages, I decided to add a tweeter instead of relying on the wizzer. Initially, I was going to use the Tang Band W8 1808. But then I thought to myself, If I'm not using the wizzer cone why not use a comparable driver without one? So, here's the questio: what 8" driver would come the closest to the venerable Tang Band W8 1808 but without the wizzer cone?

Hello everyone,
Just joined the forum! I live in Montreal, Canada ❄️! My lifelong passion for audio has taken me from creating (repetitive) electronic music in the past to enjoying vinyls (with by a glass of whisky 🥃 even better). I've always configured various media players, using platforms like xbmc, Moode Audio, RPi+DAC etc but now willing to take it to the next level (with your help please!).
Big fan of SomaFM DefCon during long nights of DIY'ing 😎 Looking forward to the discussions.
Cheers!

Offer something reasonable. Shipping costs (from Finland) are added to the sum.

Items for sale:

1) First Watt Power supply Cap banks: Dual mono / fully built with Abico connectors

2) First Watt F6 boards designed by late DIY member Georg M. / made in Finland by a quality company

3) First Watt F6 fully built PCB with Jensen transformer /Toshiba JFETs / IRFP Mosfets / Simlic & Wima caps

4) Pass Labs B1 front end / built - only connecting cables needed

5) Toroidy Tranformers 50€ / pcs

a) 2x24VAC 600VA (primery 2x115V)
b) 2x32VAC 600VA (primery 2x115V)
c) 2x50VAC & 1x18VAC 520VA
d) Triadin 2x24VAC 50VA (18 euroa)
- details in the pic

Long time lurker, finally decided to say Hi.

Name's Andrea. I'm an electronic enthusiast from nort-east Italy, I did build myself several kits and other mixed projects, and always found lots of information here.

see you around!

Tuning / tweaking of a Chinese BTL mode TDA2003 Mono amplifier.

It has some mediocre working Bluetooth 2.0 which I do not use.

If Bluetooth is needed I recommend a more modern 5.0 Bluetooth preamp.

I put on the electrolytics 0.1 microfarad foils in parallel. Also same size power decoupling foils between legs 3 and 5 of the TDA chips.

100picofarad on the inputs between plus and minus against oscillation.

There is an smps power supply I left untouched.

I put 1.3 microfarad and 4.5 ohms paralleled in line with the 4 ohm loudspeaker in order to attenuate a fullrange driver and to lower distortion by using Esa Merilainens simple resistor method for a bit current drive. More on this on his website current drive info.

For sale a pair of verry good regs for class A amps or other hifi builds.This are good for constant 10A of current and 20A on spikes.I buy some pieces positive and negative regs of this ,years back directly from Thel audio germany but today they are not more produced(verry dissapointing).I use this in all my pass aleph builds and they work without problems and with regulated psu you have way lower noise floor and much more blacker background.In music you have much more details,better and faster bass section and verry silky high section.You will become one positive and one negative reg module,so you can build one psu for up to constant 10A of current.The input voltage is from 20-100V and the output you can set by trimmer from 10-90 volts. In last picture you can see my psu for my aleph 6 build.The price I want is 200 eu for both plus shipping in EU!!!Payment by paypal or bank transfer.For more questions plese contact me.

For sale pair module original nade by Hugh Dean from Aspen.Fully working order,I used this last 5 years in my second system power amp.I only have change the input cap on each module for some verry good Mundorf Evo oil 1 uf.Module ready to play,you only need transformer and other stuff.Price 300 eu including shipping inside EU.

I have a blown set of PSB Alpha PS1 powered bookshelf speakers. They popped and died one day when I touched the aluminum volume knob after walking across the carpet with socks in winter. Oof.

They're nothing wildly special, but I like the way they look, and as a tinkerer, I'm thinking it might be fun to get them to make noise again. Most internet folks say it's a lost cause with powered speakers. There's either not enough technical information about the components, making it hard to pair the drivers and crossovers with a proper amp, etc, or the juice just isn't worth the squeeze. I'm not sure. Not having opened them up yet, I don't know what I'll find in there (not exactly easy to open), but could I feasibly turn these into passive speakers, or (possibly) repair the onboard amp and give them new life?

Thanks for your patience. Very new to this side of audio.

Hi all,

Have a blown diode from a Eaton 5PX 2000 rack mount ups that needs identifying.

Similar packaging size to your traditional 1N4xxx rectifiers.

Markings on this diode is

PJ26E
p e c 3049

From what I gather pec is now owned by Panjit but I cannot find any info on this

Cxa1800.1 volume level is chaotic.
When I have the volume turned down it is really loud when I turn the volume up the bass starts chopping it sounds like I got a wire loose but all wires have been checked and all of my splices are solderedand shrink wrapped I have went thru the manual front to back I've removed my lc1i and changed it from low input to high and still the same thing it was running fine but I changed from a cheap $5 line leveler from Walmart and it is the only thing that kinda works. I'm st a loss here talked to Todd at edburg amp repair and he sent me here specifically for papazbill but any help is welcome. Thanks

I like sound synthesizers and there's an on-line "Binaural Beats" generator here https://brainaural.com/

Aside from its intended application, it has a stereo pan function where, according to a provided LFO, it'll sweep a tone back 'n forth between the left and right channels. That tone can be set from 27 Hz up to 14 kHz. So you can take a tone, slowly (say, 1 Hz) pan it left / right and listen to that using headphones.

Why? To see how, or if, your ears work. Mine are like old tires that have never been rotated, 1/2 the tread gone on one side.

2.5 kHz the tone sounds about the same as it pans left and right.

3.5 kHz I'm aghast to find the pitch doesnt sound the same in each ear. Twee in the left, dell in the right. Swap the cups - same thing.

4.1 kHz right hears it, left not nearly as much.

8 kHz on up, only the left hears anything...

10kHz perception of anything in either ear gone.

A discussion elsewhere whether YouTube really do preserve uploaded videos audio content up to 20 kHz, or limits it to 16 kHz spurred my curiosity to look into it, and for the investigation I looked up a few audio frequency sweep test videos and chose the following video for this brief investigation.

Login to view embedded media
All audio files were downloaded directly from YouTube as an incognito user, no external download helper website were used as these services usually convert the audio into MP3 format which degrades the audio quality even further, but also the conversion parameter settings aren't known either.
As for YouTube they still offer AAC audio codec usually with the legacy MP4 video container format, but around 2011 YouTube started switching over to WebM (Web Media, usually used by online video platforms) container wherein the video comes in VP8, VP9 or AV1 codec format, and audio in OPUS codec format.

After having downloaded the various audio files I were able to grab, the files were then analyzed with Audacity, the spectrogram setting was limited between 15 kHz and 20 kHz as that is the frequency range of interest, and the following results were found:

( Each downloaded audio files file-data were analyzed on-line with: https://mediaarea.net/MediaInfoOnline
And the title above each image (codec, sampling rate, bit rate) stems from the data analysis for each file. )

AAC 44.1kHz 127kbs



Opus 48kHz 74kbs



Opus 48kHz 103kbs



Opus 48kHz 171kbs


Conclusion: As YouTube nowadays stream virtually only by using WebM (OPUS) one can consider they do support 20 kHz audio bandwidth.

Disclaimer: As this was a rather brief investigation, the results are presented as is with its limitations, there are much more info on Google Support what audio and video formats and qualities YouTube supports.

Some First Watt stuff for sale on Swap Meet. 👍 😉

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 .......

Having recently acquired a QA403 audio analyzer I looked at the linearity of some film caps I have, all ostensibly PP 100nF. I found 3 kinds of distortion profile among them, making me wonder if these are routinely being faked with cheaper dielectrics. The test setup was a divider, 100nF cap on top, 6k8 metal film resistor on bottom. This has a high pass response with -3dB point around 250Hz.

The responses I see from the three types of cap are:





Clearly cap1 is a high-k ceramic cap with high amounts of distortion evident. caps 2 and 3 are clearly different dielectrics, or very different film thicknesses (unlikely as these are all 100V rated). Only cap3 type seems to actually be PP with its very low distortion.

Here are the 3 tested samples, cap1 at top (its poor printing registration is further evidence for this being a counterfeit part):
Since these are all from my 100nF bin I don't have records of where each came from, alas, but its quite possible some are eBay, which would account for the rogues - so now I'm faced with the task of testing all my film caps...

What causes driver surround damage / distortion?
Can it be fixed?
I'm hoping somebody's going to tell me: hair-dryer or steam or some other crazy solution.

Simplest possible 1-transistor power amplifier with THD <1%

The challenge was to build a simplest possible amplifier that would be still usable. With wide frequency range, flat frequency response, reasonably low output impedance and reasonably low, inaudible THD. I am offering the result – the necessary functional circuit part has only 1 transistor, 2 resistors and 2 capacitors. 2 more resistors (discharging of coupling capacitors) and 1 supply bypass capacitor were added to the final circuit. The amplifier was designed for fun, as a circuit challenge, but the necessary condition was it must be workable and repeatable.

The circuit is a class A emitter follower with a BJT power transistor. It has voltage gain close to 1x, so it makes no voltage amplification. But it has current gain, thus also power gain, so it is a power amplifier, though with very low power, if we do not want to build it big with large heatsink. Emitter follower has almost 100% series voltage feedback, so it cannot be called “no-feedback” amplifier. Such qualification would be misleading. Due to this strong negative feedback the emitter follower has quite low output impedance, between 0.1 – 1 ohm, depending on the transistor used and also on signal source output impedance. The drawback of BJT follower is quite low input impedance, for load 4 – 16 ohm and transistor h21E about 100, we can count with input impedance 300 – 600 ohm approx.

The real circuit


Erratum: C2 = 6800 uF

C1 is an input coupling capacitor. R2 is a base bias resistor that sets the idle current of Q1 transistor. Q1 is PNP Sanken 2SA1102 transistor, just for the reason I had them in stock and they fit into my heatsink used for the amplifier. NPN transistor can be used as well in case that all electrolytic capacitors would be reversed in polarity. R4 is an emitter resistor that defines idle current and also limits the maximum current and power into the load. C2 is an output coupling capacitor. R1 and R3 are the discharging resistors to prevent loud clicks when speaker and signal source are connected. C3 is a power supply bypass capacitor. Idle current is set at about 450mA, which makes about 4W idle power loss of Q1 when supplied from 14V. Power supply voltage may be between 12 – 15V. Heatsink used is Fischerelektronik SK409/25, Farnell #4621293.
Edit: C2 = 6800uF

PCB board

The amplifier was built on a 2-layer 87.6 x 60.6 mm FR4 PCB. Produced in China, 5 pcs of PCBs cost 5.00 USD total + shipping cost. Incredible. 2-layer board is only for the reason of reliability, the solder joints would not peel off even if overheated.



Power supply

Due to not great power supply ripple rejection of the circuit, a small sealed 12V accumulator is an option. That's how I started to test it. Then I built a traditional bridge rectifier followed by a capacitance multiplier. As the current consumption of the amplifier is almost constant, the capacitance multiplier is a good choice that grossly reduces PSU ripple.




Setting Q1 idle current

Please have a look at schematics above, Fig. 1.

R2*(IE/(Beta + 1)) + VBE + R4*IE = 14V (PSU voltage) (1)
R4 = 10 ohm and we want IE = 0.45A, so R4*IE = 4.5V; VBE = 0.6V; Beta = 50
Calculate R2 from (1) as 1009 ohm, rounded to 1k
So we have R2 = 1k and R4 = 10R.
The capacitors C1 and C2 are chosen not to restrict low frequency response extension.

Real amplifier sample
Looks like this:





Parameters and measurements

Input impedance ….. 211 ohm with 10 ohm load
Output impedance ….. 0.32 Ohm with signal source with 50 ohm impedance
Voltage gain ….. 0.976x for 50 ohm source impedance and 10 ohm load (speaker) impedance
Frequency range ….. 20Hz (-0.5dB) – 10MHz, not limited by slew rate
Rise time of step response ….. << 100ns
THD at 1V/10ohm ….. 0.2%
THD vs. level and frequency ….. see plots below
Usable output power for THD < 1% ….. 300mW / 8ohm
Capacitive load ….. up to 2uF

Oscilloscope measurements

10kHz square input and output



Fast rising edge of step response, input and output



1MHz sine, input and output



Distortion measurements

THD vs. frequency


THD vs. level


THD 1kHz


IMD 19+20kHz


Conclusion

The project was made for fun, to evaluate what is the simplest but still usable 1-transistor amplifier. The circuit has extremely wide bandwidth, very fast transient response, does not care about complex load or shorted output, has still acceptable distortion. But, it has very low power, in case we do not want to build a massive heater, and has low input impedance, that is best to be driven from headphone output of mp3 player, iPad, iPhone etc. Have fun!
_________________________________________________________________

Important - construction notes:

1st sample built has part values according Fig.1., only C2 = 6800 uF. The 2SA1102 used has Beta = 60 and with this transistor idle current is 500 mA.

Today, on Dec 15 I have built a second sample. Interestingly, the 2nd 2SA1102 has Beta = 151 and R2 had to be changed to 1k8, because with 1k the idle current was too high and 10R/5W resistor would be overheated. With R2 = 1k8 and high Beta = 151, the 2nd sample has lower distortion and better measured PSR. It has idle current of 600mA, just at the limit what can be dissipated with the construction shown in the photos above.

Hi. I have a somewhat different plan for a power supply setup and wondering if there is anything inherently wrong or dangerous doing it this way.

I want to make a external power supply. It will have two transformers. One transformer rectified to dc in the external supply. Plus a second transformer in the external power supply but rectified in my audio equipment. So that part would be leaving the external power supply as low voltage ac. I want to use a multi pin avation plugs to run from external power supply to my audio equipment. Is it OK to mix the ac and dc on the aviation pin cable(4 pin cable 2 pins ac, 2 pins dc)?

Do toroids (toroidy audio grade) need to be a certain distance from the side of the chassis they are houses in?

Does each of the transformers need their own safety grounding point on the chassis or can they be star ground to the IEC Inlet grounding point?

Thanks for any help. I am still a little new to diy and don't want to make any costly mistakes.

Hello!

I'm about to build my first vented enclosure. I decided to use Markaudio CHR-70.3 again, my first project was this, sealed cubes: Cube shaped speakers

Since floorstanders require more advanced woodworking skills and I'm a beginner I decided to build bookshelf speakers, but I would also like to get as much low end as possible. So the bookshelf design can be quite large, up to 50cm height.

I am planning to build the first one(A), Mark 9 from Strassacker, since it's the largest bookshelf design for CHR-70.3 I could find online. How do these two compare?

A. Mark 9
B. CHR 70 Chamagne | Markaudio Slim-deeper bass reflex box

My questions are:

1. I assume the A can deliver better low end?
2. Strassacker site states frequency range (-8dB): 38 - 30000 Hz. How do I compare these numbers to commercial speakers which usually state the frequency range at +/-3 dB?
3. The Markaudio Slim-deeper box states resonance frequency (Fb) 57Hz. How do I compare this number to Strassacker frequency range or commerical speaker frequency ranges?


Thank you!

Hi all,

This is my first post on DIYAudio.
I have a limited understanding of circuits and electronics, but have good experience with Hifi, terminations, soldering, commercial pro sound standards, etc.

I apologise if this question/answer is silly or obvious.

I was hoping to seek some advice to help explain how this kit:
IAN CANADA CONDITIONERPI Ultra Capacitor Conditioner Board for Raspberry Pi - Audiophonics

.....would differ (performance wise) from simply inserting a few 5vdc super capacitors in parallel with my RPI power supply.

I have struggled to find much feedback on this item, and would appreciate your time and insight.

Manual:
https://www.audiophonics.fr/en/index.php?controller=attachment&id_attachment=1363

My goal is to further improve on my RPI4 power supply, which is currently the iFi power x. This supply provided an excellent improvement over the standard RPI SMPS. iPower X by iFi audio | New Ultra-Low Noise AC/DC Power Supply with International Travel Adapters

According to the product specifications the PS has a 1uV noise floor, which is consistent with previous model testing.
Power Supply (8+) Group Test, LPS and SMPS - DAC - Digital to Analog Conversion - Audiophile Style

Thanks

All other things being equal: 8" Driver, 20 litre cabinet, which system offers the best performance.

Hi everyone.

For a long time I've been looking for a small class A amplifier around 15 watts to be used as a good known reference when trying out new stuff.
I thought of the good old JLH1969 or a Hiraga. I know both quite well.

But I thought why not try to make my own, which is why I post this thread. I have'nt build it yet, as I have some questions that I hope some of you can help with.
So for now everything is only in LTSpice. I also have to mention that I am not an engineer. I am just curious about audio stuff, and I've learned a lot from this forum.
I have repaired countless amplifiers over time, but designing one is a totally different beast.

So here we go...
Most of this amplifier is quite basic, except for the output stage, which is inspired by JLH.
It is a quasicomplementary bjt design and the outputs are fed from the vas directly. There are no drivers, no emitter resistors, and no biasing circuitry.

The idea is to try feed the bases of the outputs with a constant current. In this case around 10mA. (Based on the KSC5200 spice model's Hfe).
This is done in the vas stage, which is a differential amplifier running at 20mA, sharing half of that to each output device.
I wanted to see what happens when we apply a signal, thereby changing the current balance, which results in a signal on the output.

The amplifier has fairly good data, except for the output impedance, which is very high.
Square waves looks reasonable, distortion is low as long as we stay in class a.

Here are some data. I did these sims twice, once without load, and once with load. The test sims are done with the output coil in place between the amp and the load.
The output signal is taken directly on the amp before the coil/load.

NO Load:
OLG 1KHz ~ 80dB
OLG GAIN 20KHz ~ 69dB
UGLF ~ 2.285MHz
PHASE MARGIN ~ 68.3°
GAIN MARGIN ~ 14.7dB

8 Ohm Load:
OLG 1KHz ~ 67.6dB
OLG GAIN 20KHZ ~ 64dB
UGLF ~ 2.228MHz
PHASE MARGIN ~ 68.5°
GAIN MARGIN ~ 15dB

Slewrate is around 22 ~ 23 volt/uS with 8 ohms load and a 1n cap.

Output impedance is 24 ohms up to about 1KHz and starts to rise from there !

8W in 8R+100n @ 20KHz -> Total Harmonic Distortion: 0.001033%(0.001027%)
8W in 8R+100n @ 10KHz -> Total Harmonic Distortion: 0.000536%(0.000524%)
8W in 8R+100n @ 1KHz -> Total Harmonic Distortion: 0.000110%(0.000000%)

Idle current ~ 1.5 to 1.6 amps. Each output device will dissipate 36-40 watts at ±24V

I am trying to figure out if this will actually work with such high output impedance, since high output impedance usually means the damping factor is somewhere between very low to non existant. A speakers impedance isn't linear. It's a reactive load. So probably this amplifier can't sink current from the speaker. Anyway..

The amplifier OLG drops almost 14dB with a load connected. Probably because we have no drivers, and the vas sees the speaker impedance times output Hfe.

The square waves are all done without input filter at 2V out with 100nS rise/falltime . I think it does'nt look too bad.
The step responses are at 2V and 8V 20Khz with a 200KHz square wave on top. Rise/falltime is again 100nS.

I am aware that Hfe of the outputs might rise with increased heat. I will test that in reality later on, and implement temperature control if needed.
I am also aware that the UGLF is quite high, but it doesnt seem to cause any problems. Please correct me if I am wrong.
The cascode on the input fets will probably get dropped. It does'nt seem to do much difference in this design.

Here are some pictures, and offcause the .asc file for LTSpice.

Let me know what you think, if this is viable, or it should go directly into the trashbin.

I am also interested in other designs that work like this, if you know of any.

Merry Christmas

Hi,

just some ideas about discrete Buffers for Line-Level.
I was a bit surprised that I couldn´t find some of these Buffers here at DIYaudio, so I thought I´d give it a try.

Starting with ´A´ the well known and very simple CCS-loaded Source-follower. This can give already good distortion figures and a Buffer can´t be much simpler than that. If J1a and J1b are matched -matched Duals here- one can omit with output coupling caps if the input signal is free of DC.
Beeing a singleended circuit the maximum current into the load could only be once the bias current. This means that it can only drive highimpedance/lowcurrent loads well and heat losses in the JFETs are high.
With smallsignal high-gm JFETs also the supply voltages are usually restricted to less than +-15V.
´B´ is a cascoded variant of ´A´. Here J2a and J2b run much cooler, since the cascode JFETs J3 and J4 provide for low and nearly constant Drain-Source voltages. J3 and J4 may be high Idss low-gm types, which take over most of the heat losses. While the load drive capability is nearly the same as with circuit ´A´, the distortion figures are considerably lower. If J2a and J2b are closely matched, the output offset will remain low enough that no output cap is required, even with unmatched cascode JFETs.

Circuits ´C´ and ´D´ are an idea -I haven´t seen it here before, but very probabely it´s nothing new at all- to increase load drive capability.
It resembles characteristics of a Sziklay- or Compound pair and cascodes.
Circuit ´C´ could probabely named HCC, Hybrid-Cascode-Compound, circuit ´D´ could be called FCC, FET-Cascode-Compound.
Both only differ structurally by the useage of PNP resp. PMOS as output devices.
The voltage drop over the cascodes drain resistors are used to bias and modulate the output transistors.
The two circuits allow to drive much lower impedance loads than ´A´ and ´B´, due to the much increased bias currents (10x and more).
The extreme short and direct feedback loop of the Sziklay pair preserves the good THD-values of the cascoded JFET stage. Since the JFETs may run on smaller bias currents (more degenerated with larger source resistor values) and drain voltages, they run alot cooler. Temperature and temperature drift issues are lower. The Potis in the CCS-JFETs drain allows to tune the output offset, so that no coupling cap should be required. Tolerances of the PMOS might be checked though.
Headroom is lower than with the simpler circuits ´A´ and ´B´, especially with the PMOS output devices of ´D´. With +-15V supplies ´D´ is capable of 4Vrms which is more than sufficient for typical high-level applications.
´D´ shows slightly better THD than ´C´ with highimpedance loads, while ´C´is slightly better with lowimpedance loads and can drive up to 6Vrms.
Using the simmed devices (all in SMD) one could use the same layout for ´C´ and ´D´ for easy evaluation and comparison.
Does anybody recognize some hidden drawbacks apart from possible need of matching the PMOS?

jauu
Calvin

I have for some years been using the DIY edition of the Minidsp 2x4HD without DAC's, named Nanosharc. I have sent the I2S output to two Soekris 1021. Their solution has worked really well for me, the software is easy to work with, and it worked well with the two inputs.
After a firmware update, the unit sends no sound, neither from the Toslink or USB input. I am in contact with Minidsp, but they are slow, and although I still hope for a helpful feedback, I hate being dependent on them for my lovely sound system to work. What else can I do to keep the two Soekris DAC's? I am looking for a kind of DSP solution where I can send two I2S signals after crossover and other DSP processing.
Any advice will be helpful.

I have a PSB Alpha PS1 Powered Speaker System with a blown woofer. Need help where to buy parts. 3.5" Woofer. 8 ohm 40W. any help would be appreciated.