This very simple design has all the ingredients to satisfy even the most demanding DIYers. The output power in pure class A operation is 15.52 W at 2 ohms and 1 KHz, or 7.76 W at 4 ohms and 1 KHz, or 3.88 W at 8 ohms and 1 KHz. THD is only 0.025 % at 15.52 W and 1 KHz (2 ohms). THD is only 0.0024 % at 7.76 W and 1 KHz (4 ohms). THD is only 0.00091 % at 3.88 W and 1 KHz (8 ohms). Voltage gain = 8,9 dB.

Only two stages. Four transistors. Very few components. Its performance is surprisingly good, despite its total simplicity.

High bandwidth. Ultra low distortion. Input in single ended configuration. Output in single ended or push pull configuration, entirely adjustable by the position of a trimpot. PSRR: 61 dB across the entire audio bandwidth.

I want to hear comments from those who intend to build this simple amplifier.

regards

Here are the first dirty tests. The microphone does not reveal all its high quality. The tests were between 1A and 1.3A of bias current, levels at which the amplifier should give lower quality than stipulated. The loudspeaker impedance tests = 4 ohms:

Amplificador HDC 20W (Clase A) Parte 4 - YouTube
Amplificador HDC 20W (Clase A) Parte 5 - YouTube
Amplificador HDC 20W (Clase A) Parte 3 - YouTube
Amplificador HDC 20W (Clase A) Parte 2 - YouTube
Amplificador HDC 20W (Clase A) - YouTube

Hi - I'm looking for:

• Seas A26RE4 10" drivers (pair)
• Morel CAT378 tweeters (pair)

I'm located in St. Louis, MO 63108 USA.

Let me know if you have a nice new pair from a project you are no longer interested in, or perhaps a gently used pair.

Thank you!
Tom

Hi,

Building this DC power supply, ~36v out.

I’d like to add a bleed resistor and LED for discharging the cap banks if they unloaded, what spec do I need?

Would be great to know how to calculate it for future projects too, thanks.

I haven't seen this in these forums...

This is an interesting article and it describes the Hafler quad circuits, plus others. Pretty simple actually.

https://midimagic.sgc-hosting.com/quadmuse.htm#evmatmul

As it turns out I got four matching speakers laying around and the amps to drive them ( four Acoustic Energy AE1s and a bunch of amps...)... I was thinking of trying something like this is my office. I mean, I got two quad receivers but they are huge and won't fit on my desk... but a small decoder like the ones he described might be a fun project.

----------SOLD----------

I'm selling 3 pairs of Aleph J populated boards and 2 Antek transformers 600VA 18V (come with hardwares but no screw). Boards are sold as pairs. Transformer is optional or can be sold separately.

MOSFET are measured and matched from a whole factory tube (48 MOSFET). Matched Toshiba 2SJ74BL are genuine parts from Spencer. Quad matched, 10.65mA, 10.68mA and 10.73mA.

All of them are pulled out from perfectly working a 6 channel amp:
https://www.diyaudio.com/community/...rated-build-guide.241729/page-87#post-4641691

Measurement
https://www.diyaudio.com/community/threads/aleph-j-illustrated-build-guide.241729/post-4641659

I would like to sell them to experienced DIYer, and I will not offer any post sale support. MOSFET might have to be re-soldered to fit your heatsink holes perfectly.

Please make an offer. Thanks!

----------SOLD----------

Got this amp in and noticed 1 of the rail caps vented .

I replaced the rail caps and went to power the amp up and another cap that connects to the negative regulator vented .

Also noticed there is a burnt trace on the bottom of the board .

Any ideas what might cause this ?

Hey everyone,

I'm bummed I have to ask for help but I find myself just totally lost. There is nothing for me to reference in my car. I drive an E46 Coupe, so the equipment gets mounted in the back left corner of the car. The bottom floor isn't flat. The left wall (towards the quarter panel) is not flat. Without two points to create some "squareness" it's hard to engineer a mount. What's worse, is I also have two pieces of equipment from the car (radio and navigation module), and the navigation module can't be mounted vertically because of course it can't - it has a CD in it. It's also poorly shaped because the wheel

Here is everything I have to mount:

• Stock Radio
• Navigation Module (7.375 x 6.5 x 2.375)
• JD 400/40 4channel amp (9.5 x 7.5 x 2.125)
• Alpine S-A60M (8.0 x 8.125 x 2.25)

The stock mounting isn't ideal.
It has a tiered shelf, pictured below. The radio sits in the middle of the vertical mountings, and the stock amplifier mounts to the far left/quarter panel, but the stock amp is 1.375" thick. When mocking in the Alpine amp back there, it would touch the chassis. When mocking an amp in the most inward position, I'd have to do a lot of trimming if the metal bracket and there still isn't a home for the second amp. Also, the amps would be stuck below the navigation module, which would potentially trap a lot of heat.

I proposed a new design where the radio and navigation module where would be stacked on top of each other horizontally and then have the amps on top, mounted vertically. Each of the amps are roughly 5lbs, so that's 10lbs mounted vertically. I track the car, and in my last track day I was holding 1.3 sustained G's, so that mount front the horizontal section to there vertical has to be sturdy. I just don't know how to go about this and am tempted to take it to an audio shop. That would just feel like defeat and ANY help from an overall solution to designing one would be appreciated.

I have a pair of drivers and want to make a pair of reflex desktop speakers which don't have visible ports. This is a kind of follow on from here:

http://www.diyaudio.com/forums/full-range/173553-fr88ex-based-micro-onken.html

I'm aware that I'm pushing my luck a bit with a narrow box and the alignment is not quite what I wanted, the ports are a tad long, but it's close.

Oh yes, Martello is a kind of small and simple castle and I remember somewhere there being downward ported speakers that are known as castles

Driver Review: Comments: This is without a doubt the highest performing 3" I've come across, at least on a few fronts. The motor is an underhung neodymium design and the cone is thin (and fragile) formed aluminum. The only negative is a slightly ragged top end that may take some filter work if used full range, but I'd generally recommend a cheap and small neo tweeter placed close and crossed over high. There's a lot on the positive side, like high sensitivity, a clean low end and smooth midrange response. The frame is cast with ventilation under the spider, but users will have to pay close attention to airflow behind the cone - It's even more important to chamfer the inside baffle opening and in this case likely use a thinner baffle material as well. Tested June 2009. [Zaph: http://zaphaudio.com/smalltest/]

Another Martello build here: http://www.diyaudio.com/forums/full-range/188569-fountek-fr88ex-3-build.html#post2564558

has anyone used multichannel HT receivers to power active speakers?

At the moment I am prototyping a 2 Way OB and applying the filtered/equalized line level signal to the multichannel input of a 6.1 channel Onkyo amplifier. It has individual level control for each amplifier, and the master volume of course.

Pity the multichannel input is only 5.1, so I cant access the center back amplifier at the moment. Looking at the amp schematics I have some ideas to access this channel and keep some of the level control as well as the master volume. Further option is to feed the signals directly to the power amplifier board. I saw some HT receivers with 6.1 (or higher) multichannel inputs, so these wouldnt need any hacking.

I know there is a lot of cheap amplifier boards on ebay, but I like the idea of recycling and to already have everything packed in a nice box (with input RCAs, speaker binding posts, level and volume control...)

Anyone has tips and tricks how to reuse these relatively inexpensive (I paid USD 50) "obsolete" receivers in active speakers?

cheers, Erik

I was about to order some heatsinks from the diyaudio store, just like many times before, and like many times before, it automatically pre-populated my name, email, phone and address...when I go for next page to pay, it says it can not ship to the address I provided.
Well, I do have the same address last 5 years, and I purchased a dozen times from the diyaudio store, to the same address, so I am not sure what the problem is.
Any suggestion?

Hey folks, I've got this Audison I'm working on and as far as I can tell the class d driver circuitry is a fairly novel design. It appears that the triangle wave is generated by a 555 timer which is then fed to a high speed comparator. After that it gets fairly odd, I haven't studied it very in depth yet, but it appears that the outputs are driven by high speed optocouplers, and not driver transistors like most amps.

I'd love to get a service manual for it, I'd be happy to pay for it. I'm trying to get an idea of what it's going to cost to repair it. It only blew a few power supply fets, but with changing all parallel parts and compliments it's going to mean full rebuild of the supply. I got the supply running with minimal parts and moved on to the power amp. It had one shorted fet in the power amp, I swapped it just to do testing on this class d driver circuit, but the amp will not power up with the output daughter cards installed. It flashes a code on its status LEDs, but the manual doesn't detail what it means, just that it requires service.

I'm mostly wondering if anyone has come across this class d design before, and if you might have any pointers.

I have tannoy 3808 drivers, 15", I understand from SRM (Super Red Monitor)

I dont have correct crossovers

Can anyone help with a circuit diagram or even the real parts !
A diy version without tone controls would be simplest and cheapest, probably sound best too.
Ive seen the diagram on here for the 12" version, I assume similar but not the same ?

Hi all of you, for my upcoming projects I need fast low cob vas trannys , the above were chosen. If any of you have a stock to share of originals , pnp npn hfe same grade , get in touch. I need about 12 pairs .. thanks

What is the best and most reliable 6S 18650 protection board I can get, that actually does a good job at balancing ?

I am new to recording but have some thoughts afte watching recent mofi debacle, on their recent original master record claim,

t is know that back in the reel to reel tape Era everything is recorded analog is all the neessary harmonic is retained, when we are going to digital era due to sampling their information in the recording is missing.

now I was wondering in todays digital age is one microphone recording all the freqency specturm is not the corect way to record, we should use around 4 microphone ,1 is the cordination recording all frequency, and 3 other miciphone recorde at the freqency specturm they are prefect at. After that the recorded cue will be mixed toether . Or is the r2r and delta sigma ADC method is incorrect

This is a similar idea of sigma camera optical sensor (Foveon), which it has 3 /4 layer which readers a specific light wave in a window then combined togthers (analogue recording), while traditional bayer sensor use interpolation method (digitaltized recording)., however HDR recording is easier at bayer sensor , so differnt optical exposure is used when taking picutre and combine to former an image which rivial Foveon sensor)

]i understand JM47 is a Neumann clone-
the t.bone SC 450 and mxl v67g are looking good to replace, but they are priced very differently - t is £68 - mxl is £100 - will the mxl be slightly better components?

Main question- will the mics be as good as an older jm47 or mxl 2001?

Up for sale vintage LED VU meter from legendary BEAG, EAG/Telefunken mixing consoles.
Pure analog circuit with 33 LEDs, indication range from -60dB to +5dB in analog domain, or percents.
Device circuit accept balanced signals, also can be used with non-balanced lines.

Setup include original power supply unit (PSU), bipolar +/-12V, 2A.

Type of VU meter : MAK113
Size:
Tallness, indication panel - 243mm, circuit container incl connector +140mm, overall incl connector - 375mm.
Wide - 50mm, Deepness, max 120mm

Type of PSU: THE143, 220-230VAC,
Size: W200mm, H120mm, D160mm (incl connector/heatsink)

Overall, setup in excellent condition, only non-smoking studio use, and looks gorgeously.
Circuits of both modules (with "M" letter though but OK):

VU Meter

Power Supply Unit PSU

Initially, rig offered with 3 native connectors, with temporarily harness for inputs and PSU, however harness can be performed based on your wishes, for add fees.

Price - 230,-eur

Item will be packed carefully with international tracking across all distance.
FREE shipping across EU/UK.

---
See also my other items, small items can be added into box:

• UTC 4x A-22 transformers, NE 5:1
• Canare L-4ES6 pro mic cable, Japan, 4 wires instead 2 to supress all noises, uniq offer - 9 colors
• Celestion G12T-100, guitar loudspeaker, 100W 16 Ohm

• Triplet ultra rare 4.5 inch meter
• never used big Simpson 4 1/2 inch meters with relay needles
• vintage detented/non-detented attenuators Daven, USA
• mains distiributor Tripplite, rack 19 inch, for USA 120V plugs
• Web Cam for Sony Bravia TV set

Few different items - Meters, Caps, Cam, Cable

Set of 4 excellent UTC transformers A-22, Northern Electric

* * *

Hello everyone

Sometimes 1 of my concertos , did't immediately play at full volume. Only just a little, often crackling sound came out. But after a few minutes, that one concerto then started to play at full volume.

So i thought maybe it could be the bad contacts of the crossover.
So I cleaned the crossover.

When I reassembled the crossover, no sound came out anymore at all...
So I took the crossover from the other concerto, and I placed it in the first concerto.

But the concerto didn't want to play anymore with this ‘new’ crossover either.

So I placed the crossover back in the other concerto again.
But, now that other concerto didn't want to play anymore either... Both concertos are dead now...

What could I have done wrong?
I first cleaned the crossover-contacts with IPA (Isopropanol). Also the crossover 'holder'.
Then I sprayed a little Griffon contact spray on the crossover-contacts and the crossover-holder.

Perhaps this can have caused a short circuit?
What do I do now ???

A friend gave me two Sony 211-12 16 ohm Alnico magnet drivers. I'm looking for cabinet recommendations for these drivers. I want to use them as a "single driver" speaker. Does anyone have experience with these drives? These aren't "coral holey basket" drives. I'm going to measure the VAS this weekend after I build a test box.

hey guys

im opening a thread in the goal to ask for those who used the audax pr170mo and eventually moved on, which midrange driver you prefer and why?

Ive tried the PHL 1120 so far and i prefer the Audax.

cheers

Hi guy's, just spotted this Hypex amp complete on AlliExpress for around $400 delivered.

https://www.aliexpress.com/item/100...016590466213748839efa93!12000029205669537!sea

Currently using a TPA3244 power amp, would this be a step up, wattage is OK for my smallish room.

Cheers

Hello

Pls link me to more info about Aleph M (or mini???). Manual, circuit diagrams

TIA

I made it. And I have several chips. But I'm still not interested in assembling it.
I don't think this product is suitable for DIY. It is more suitable for Xiaomi and Huawei. Or other industrial products.
I provide Sch PCB information. If anyone is interested, he can process it.

I am loocking for the Sierra Performance Labs. Are they still in Bussines? The German distributor (Hermann Hoffmann, Audio Int'l) died this year and I can not find anything about them. They made beautiful Air Motion Transformers.
Does anybody kow something about the Manufacture ? Their fate? How to reach them if they still exist?

Hello, was wondering if anyone has tried to cut and splice cables connectng to LIFX LED strips? I want to conceal the lights and the 1/8"-thick cable inside my project and cutting-splicing seems to be the only way to do it without drilling huge holes. It's a four pin strip. Any suggestion would be appreciated! Thanks, h.

Hello all,

I came across a hi fi tube amp schematic that loosely resembled a Williamson type topology but had included a cathode follower between the phase inverter and the power tubes.
I was curious to what you would expect the inclusion of that stage to offer in terms of both advantages and disadvantages, mostly relating to effect on potential output power vs any other characteristic.

Thank you,
Best,
PJD3

I haven't used my KEF Kube-1 in quite a while, so when I got it out today I found that the crossover pot has broken. I would like to try and replace the broken pot myself, but I've no idea what type to get, or even where to get it. Can anyone give me a bit of advice on this?

I'm looking for recommendations for a DIY DAC - preferably bare PCB, I can source components and build power supply etc. What's currently out there?

I appreciate this is a bit of an open question - ultimately it's to go in my main hi-fi, 2 channel only, CD and raspberry Pi (Roon) sources, optical and coax inputs would be useful. Not too worried about USB input. I've got plenty of experience with DIY builds but most of these have been pre and power amps (SS and valve).

My preference would be something with a flat/linear frequency response, or at the very least something that someone has done some meaningful measurements on so I can check out performance of the design before spending my hard earned...

Hit me up with some suggestions 🙂

I am buying some Panzerholz for a turntable plinth but I have to buy a whole sheet of it. I havent got a price yet but wanted to see if there is any interest in buying the rest of the sheet that I won't need?
update
Cost will be $75 a square foot. Shipping cost me almost as much as the wood did. plus import fees etc..
Jeff

Hello, i'm building active subwoofer with FLI" 300W, 4 ohm speaker.
Sealed box, powering it with TDA7293 x3 parallel(these from ebay).
What i need is filter, ofcourse. I've ended up with these two:

P48 Sub-Woofer Controller (Rev-A)
Low pass filter - Subwoofer :: circuit diagrams

And i'm not sure, which one i should choose. Seems like 1st one has phase and gain controls, while the other has freq cut-off and gain controls. Which one would be better for sound quality(meaning nice low freq), or should i make both, and compare them 😕

Also, i would like to make over-voltage protection for my subwoofer amplifier input(in case filter goes down, it could feed +-12V into amplifier's input..?) Something like: http://1.bp.blogspot.com/-yvrNe0grMz0/U8K40NUUg3I/AAAAAAAADSA/YjH5BSjBbzc/s1600/vprotection.png?

Thanks

Hi All
I have picked up 2 Quad ii power amps.I have fired them up and they sound lovely.However as it was last serviced by Quad in 1984 (although used very little since then)
I guess some bits will probably need replacing.
I would like to keep the outside pretty standard looking and not cut any chassis so am looking into iec mains socket and phono input that can fit in the holes already there.
In terms of components I am going to replace R12 180R with a 6.5 watt Vishay Dale Wirewound and the C5 22uf with a modern electrolytic.
In terms of the valve coupling caps(0.1uf )are Ansar 630v ok to use?I understand I have to add a 1nf cap in parallel with R11 if i use non metal body caps for C2 and 3.
Also if anyone has experience does the quality of C2 and 3 affect the sound quality.
Many thanks for any help.I will measure the resistors tomorrow and poss the main caps might need doing.
I have had my multimeter and lots of transistor amps but as I have had a few shocks in my life I think a good regard for the voltages in the Quad may be advised..🙂
Appreciated
John

Bonjour à tous, voilà !

My article on IEEE SPECTRUM was a reconstruction of the very first analog to digital converter in 1942 used in SIGSALY Quantizer, part of the top secret unbreakable speech scrambling system.

I am interested in the forum feedback and interest.

https://spectrum.ieee.org/rebuilding-a-piece-of-the-first-digital-voice-scrambler
https://spectrum.ieee.org/sigsaly-analogtodigital-converter-construction-and-debugging

Bon Soirée

Jon
Paris
ARCSI.FR

I have been repairing home/professional audio equipment for 15 years as a hobby. I have learned the power of schematics. Just wondering for those that repair mobile audio equipment how does one start to diagnosis without a schematic? Are there any universal schematics since alot of mobile power amps are similar. I purchased a new used Dual XPR522 and it has operated well for months. Now there is an intermittent static noise on the right channel. Removed amp and put it on the bench and powered it up with speakers and confirmed it is the amp. Monitored DC offset on right channel and at power up 15mV after several minutes it increases to 150/200mV. Took it out of the aluminum shell and have it bare board on the bench. Nothing smoked or discolored. Wanted to inspect solder connections and traces......suspicious of a bad solder joint.
Being one channel it is not power supply related. Most likely something in the amplifier stages.
The intermittent static noise is not affected by volume.
and I already know that this amp is probably considered a throw away but I am one of those individuals that cant bring themselves to throw away a piece of electrical equipment that possibly just has a bad solder connection.

Hey!
What are experiences with speakers from Lii Audio?
Which ones have you tried?
Is anyone impressed?
Regards

Used Hitachi 2SK227 (K227) Silicon N-channel Mosfet. See picture from datasheet for more details. The mosfets were taken from a Rausch DVT PA-ampflifier. The 2SJ83 is the
counterpart to the chip. I have not tested the mosfets but they seem to be in good shape. These mosfets are very hard to find!


$8 each plus $5 in shipping world wide (Each Additional Item +$1)

5 AVAILABLE

To whom It may concern,

Anybody who knows where I can have this MAS Solitaire MK-1 schematic diagram?

Thanks,

John

hello,

I picked up a really nice PYE TEN mono amplifier. i was getting a weak intermittent signal and found the track to one of the power transistors was broken so i repaired this and have a bit of the normal healthly low level buzz to show the amp is ready to output sound.

Problem is I think the previous owner may hay messed with the volume tone wiring and possibly rewired it wrong from the rough soldering and it appears to be missing a purple wire from 'F' and only has a film cap. i cant make the wiring how it should be.

the pots from left to right are....
selector (input orange + blue)
volume 25k then tone 25k.

if any one has worked on these or similar model and knows the pin lettering or can identify how the tone/ volume pot wiring should be that would be great to get it working again. thanks

update i disconected the pots from the pins and have ran an audio signal through to pins B/A.
have used a blue tooth speaker to ground try extract audio from the other pins.

pin D i got motor boating
pin E motor boating plus very rough audio signal
pin C acceptable slightly clipped audio signal

I have managed to get some scratching from the test speaker by rubbing pin F to Chassis. Have tried inserting an audio signal to pin F but there is no output to speaker.

I think it may have bigger problems so may just use the chassis for a project.

Hi, im here again with my amp and now i designed pcb and i would be very glad if you can me tell if its good or if i can somehow improve my design.
Everything is in attachments. If you need something more i can add it. Thank you very much for your help guys 😉

hi there anyone got a schmatic for the "marshall origin 20" model or120c.

I have not plugged it in yet but am told it goes ok for a couple of minutes the just fades out.

schmatic would be good or if anyone has experience with this model and has ideas as to cause of fault please chime in.

all rdy noticed that the output trany is connected to circuit board with spade connectors which are quite lose, but i don't think that's the problem

Just seems like the most eloquent solution to directing the correct frequencies to the correct amplifiers without additional external wires and separate power supplies. I have Wayne's line stage board and the NP x-over board. Any interest in the community to merge these schematics? Peace

Hi all,
Can I connect the grounds of these two supplies, is this OK? I have popped the snubber cap on the negative rail (47u) and the regulator is kaput. I'm not sure if the cap was connected in reverse but, I replaced the regulator and cap and also disconnected the indicated ground and it's all good. Was it the cap or the grounding I'm not sure. I'm also not happy that this 338 burns with a reverse cap, if thats the case... (24V adjusted output give 35 after the pop and cap replacement... source is 40)

I'd like to share my experience with Beezar audio (beezar.com) as I couldn't find a section dedicated to web shop review.

Beezer Audio is an awesome shop.

Prompt shipping, fantastic online-documentation and AMAZING after-sales from the owner (Thomas).
Highly recommend this shop, plus you support a sole proprietor!

I bought two DAC's and two high quaintly USB power supplies, both a DIY solder kit.
As both kits require some advance soldering (I am a novice) I wanted some additional information before the purchase contacted the store with some questions over the 4th of July weekend.
Within a hour I got a detailed response back from the owner. Which was excellent.

Both kits have very detailed website, with amazing instructions and photos, which were a great help and the level of detail is truly amazing:
http://www.diyforums.org/PupDAC/PupDACoverview.php
http://www.diyforums.org/Doodlebug/DoodleBugoverview.php

Shipment was quick and without any issues.

As I am new to SMD soldering I broke two tiny components.
Luckily the kits come with a bill of material (see websites) including Mouser and Digikey part ID's
Yet due to supply chain issues the required replacement are back-ordered for >12 months.

I contact Thomas on advise on alternative components I found and whether these would work.
He confirmed the alternatives would work, but offered to ship the needed replacement parts (he had on spare) for free!
These are components I broke and he did not needed to replace these at all, yet he did for free!

Since then we exchanged emails a few times about the build process and he's been very supportive and patience.
Awesome!

So, overall excellent service, great communication and thanks to the on-line documentation I greatly improved my soldering skills.

p.s. Im not affiliated with Beezar Audio in any way nor paid to write a review. Just a happy customer.

I have tried a few searches on the site but can find no threads on single MOSFet Class A amps with inductive loading. Has anyone successfully done this and can tell me about it and what they did? Any schematics? Should this continue as a new thread?

I have built my own single MOSfet amp with resistive loading but understand inductive in the source leg can be achieved.

Please find photos of the above. Does anyone have the original article?

Hi there

I revisited the laser etching method used by some for PCB's using it for aluminium laminated foil is a bit harder though 🙁

Part1 - Test ! piece
Login to view embedded media Part2 - Actual size test foil
Login to view embedded media Part3 - Reason why i am not going to use a foil like this for my current build
Login to view embedded media

Assembled and tested 3-phase sine wave generator and output board, dialed-in for the BLWS motor suggested in the thread.

$150 shipped USPS Priority in the US.

https://www.diyaudio.com/forums/ana...sinewave-generator-turntable-motor-drive.html

https://www.diyaudio.com/forums/analogue-source/307918-3-phase-class-amp-diy-bldc-motor-drive.html

Hello good people of the internet!

The short version is: I want to transform my Sony WH-1000XM4 into an aviation headset
This is nothing new, I've seen plenty examples of people building aviation headsets from consumer headsets. There are even companies (I know of 4) whose sole business is selling these adapters (for $200-$300, which seems a bit steep). On diyAudio, I read this topic and that topic but they don't answer all of my concerns. I know very little about audio but I'm handy enough with a soldering iron and 3D printer.


What I understand:

• the aviation panel expects a load (is it called a load?) around 300-600Ω
  • I measured the resistance (with a multimeter in DC, I don't have a function generator, nor would I know how to measure an impedance with one anyway) of my cheap headset between 130Ω et 1300Ω (there is a potentiometer that makes the value change)
• Sony says the WH-1000XM4's impedance is 16Ω when turned off (but wired) or 40Ω when turned on (still wired). I will use them turned on 99.99% of the time since the goal is to have active noise reduction.
  • This article says around 17.6Ω average, I guess it was with the headphones turned off
  • I measured the resistance (still with my multimeter) of the WH-1000XM4 at around 50Ω (turned on or off. This isn't surprising since the article above showe impedance is way above 16Ω at low frequency)
• Some people use an impedance matching transformer in their designs, some people say a potentiometer is enough

What's a bit hazy: If I go from the mono audio signal of the panel to my stereo headphones, will I need to wire L&R in parrallel? Will that divide my impedance by two?

I don't want to damage the aircraft's equipment, nor my fancy headset...so, should I use an impedance matching transformer? If it's not 100% necessary, what's the drawback of not having one?
How to choose it? Does it need to be specifically, say 300:20 or can I use any transformer that has a ratio around 10:1?

Should I include a potentiometer?


Thanks for your future answers

So, just a quick post to share a successful repair I just did to a Philips CD150 which I got for almost nothing, with the indication that it wouldn't read any CDs (showing Err). This turned out to be a hard one to diagnose and in the process I learned and discovered a lot about philips cdm transports and this player in particular, so I think this can be very useful for some people, although the player itself was kind of low-end at the time, it still sounds quite nice. If it was one of the better ones (let's say, TDA1541 at least), I'd now start modding it as I did with my Marantz, but like this, I'm simply going to sell it cheap. This was more for learning than anything else.

Here we go:
first things first - I opened it and cleaned the lens. Nothing improved.
I then took my mobile phone camera and "made a movie" of the laser lens when hitting play. It showed that nice tiny red dot and also the coil moving up and down, so laser and focus was working. Decided to clean inner lens (which is quite easy with the CDM laser head). No improvement.
Next, I searched the internet for the service manual (first I didn't get the manual for the CDM, only for the player). Found out about the three service positions. Tried them out and the player clearly passed stage 1 and 2, but then, the number 3 would sometimes appear very shortly but it would immediately stop and go back to 0. Sometimes even with the swing arm making a hard stop against the limit.
I tried the Fast forward and Backwards keys to move the swing arm, responded well, although sometimes would engage in a strange kind of "stutter", I mean, it seemed to get stuck, vibrating. Very odd.

I starting measuring, laser voltage seemed ok, although it would vary a lot, depending on the actual position/state, but I guess that's normal.
Measured all supply voltages and got kind of confused - it didn't measure +-9V, but +12 and -13V, which is very high for CDM, I think. So I (mistakenly, as I discovered later) thought there could be a problem with the power supply (transformer hums audibly), checked all, even changed the supply wiring to 240V (was 220V), didn't make a change, then I even built a little regulator circuit with LM317 and 337 to feed clean +9,5 and -9,5V to player, which turned out to be a waste of time - player behaved exactly the same way and the regulators would get hot, would need large heatsink, so I ditched this idea.

Next and after searching and reading a lot on the internet, I decided I would recap the servo board, as frequently the electrolytic caps have dried out, especially those blue Philips axial, the infamous C2103 especially. So I did this but nothing improved. Then, when I was trying to measure some stuff (was starting to think that the problem would be in the radial drive, for example the driver IC), while suddenly the player advanced to service position 3!! 😕 I was confused and surprised and immediatly decided to try it out to play a CD, connected to my amp, and well, it played! Music sounded good. But it stopped after 1 minute and didn't play again...

So, now I knew that the laser and transport should be fine, as well as the DAC and general control circuitry, although it still could be the radial drive or something, which caused it to loose tracking or not play at all.

I got myself the service manual of CDM-2, but then actually found out that this player had received a new laser head, the CDM-4, somewhere in the past, as the servo board was CDM-2/29, if I'm not mistaken right now, but the laser is CDM-4. This was interesting and I actually found the part where Philips indicates exactly what has to be modified to be able to make the CDM4 laser work with the old servo board. I checked all of the adaptations, I mean, I didn't know the history of this player, maybe adaptation was made wrongly? But no, all was exactly as in service manual.

I was getting a bit desperate and was running out of ideas. But then I had an idea: what if the player would need to warm up to be able to play? As I had it on when I was measuring for quite some time! Well, I left it on half an hour. And guess what? It worked! Not perfectly, but would play here and there.

I then searched the internet for this and found the solution: it appears that Philips at that time used so called "griplets", which seem to be a very frequent problem on more well known players like CD104, for example, and can cause all sort of problems which generally go away when player is warm. What seems to happen is that the solder in those griplets (which connect one plane of the PCB to the other) has cracks and doesn't conduct well anymore, while with heat and thermic expansion, it starts to conduct better.
So I decided to take care of the main decoder board, as it was the only PCB with griplets and in the process also recap most of the electrolytics.
I didn't drill the griplets, as they recommend for CD104, as here each and every of them leads directly to ground plane and some have one leg of a capacitor in it, so I simply sucked out the old solder with desoldering pump and scratched a bit of the copper on the top layer to get the oxidation off and then put quite a lot of solder to reflow the whole griplet and solder to the scratched place to make sure it had good connection to top ground plane.

After all this, I tried it out (cold, obviously) and bingo!! Worked!!! 😀😀
I took the opportunity to verify laser voltage adjustment, which was perfect and made some other measurements, all checked out fine.
Problem solved! I tried it out with several different CDs, some pressed and also quite a few CD-R, it reads all of them, although it takes quite some time to read the TOC of a CD-R, which doesn't happen with pressed CDs, there it's very quick. Takes some 20 seconds to read TOC of some CD-Rs. But then plays them flawlessly, no skipping, and goes to all tracks, even 80 minutes CD. So I guess that's normal.

While testing, I also found another problem by mere chance (and am glad that I did!), one of the connectors to the display board was too loose, I tried contact spray and whatever, but it would loose contact when I'd touch the wires and scramble display and make controls not working. I decided to go the radical route - I just cut the wires and soldered them directly to the board. Problem fixed.

Ah, before I finish: I upgraded the power supply caps while recapping, put some much bigger ones. And I had to make the tray working again, with a new belt (not original, but works), but that strange door was causing problems (why did Philips make a door? had never seen this!), decided that the spring was too tight, so I simply cut a few of the windings of the spring so that door would stay shut but open much easier. Problem solved!

So, I now have a fully functional CD150 for sale, I'm listening to it as I'm writing this, sounds nice. Learned a lot with this one.

Ah, and last but not least: as I didn't have access to original Philips BC capacitors, which apparently are the best for that (in)famous C2103, I decided to install a 47uF capacitor of a not very well known and certainly not expensive brand. As I had read that it shouldn't have low ESR and that a bit more of capacity actually could be good. And well, it works perfectly, AFAIK, no reading or tracking problems and laser voltage stays precisely at 49,8 mV. Was I just lucky? Or is this capacitor not so critical in some of the players or, just an idea, if they are upgraded with CDM-4 on old servo board, as this one?

A couple of photos after cleaning, recap and player working fine (didn't take at details):

Hi, long time no see!

recently i got from a friend a good old amplifier from rockford fosgate. Its the P8004 4 channel amplifier, which stated in its name.

Amplifier was working ok but suddendly stopped working from one of their 4 channels. Short yellow led lit, so we removed from the car and bench test it.

None of the 3 40 amp fuses blew, and the amp still worked on the 3 remaining channels, good clear sound, no distortion.

Front left channel blew (a low pitch tone), so i discovered my friend wired in paralell an infinity kappa speaker , 2 ohm, with another focal 6 inch speaker, 4 ohm, so, yikes! Thats 1.3 ohm so way low from the 2 ohm stereo per channel spec!

Well, i went to test all the transistors, so the first row of two 28n15 were bridged to ground, got 0 ohms each way. The another ones (fqa36p15) werent shorted, and tested all the transistor, and they at least were not shorted.

So i ordered a pair of 28n15, installed them on the MEHSA strip (god, that was not easy!), and discovered two of the small condensors on C117 and C118 blew in half. Weird! I said, maybe i damaged them without noticing.

I searched on the net, and found schematic of the amp, so , if my memory serves me right, the replacement part i need its a “ 104- condensador de 0.1 microfaradios, 50 Volts, 5% tolerancia”. That being said, i jumped to my nearest electronic parts supply, but found a part with +80% -20% tolerance range! So i am stumped if i can use this part, or if i need the exact replacement.

i am attaching some pics of the amp board, pics of the schematic from rockford, and pics of the replacement part i have readily avaible.

Thanks in advance, sorry , english its not my first languague and electronics are not my field of work (i am a fireman), i hope i have been clear with my explanation.

2 pcs available, see photos. Never used, from surplus (Pollin surprise package).
€/$ 20 per piece
shipping to EU: €6
others: please ask

Payment: Paypal only

My mate has a 2 way speaker and in the photo of the crossover the 10ohm 50w resistor has blown hardcore and I reckon the cap was ok but the resistor popped so hard it shot a flame out and scorched the cap. Does that look like what happened? and what could cause this? It's the second time that resistor has blown :O
HF diaphram is open circuit but not burnt actually it still looks new.

Hi all.
Quick question that has likely been posed before:
If building a push pull DHT amp, e.g. Pete Millett 6A3 mono blocks, and using a single tentlab regulator per power tube, is there any benefit to having separate windings per regulator or can a single high-current winding feed both regulators without any significant penalties?
Thanks!

Thought I would share. Feedback is appreciated.

I picked up a 12' stick of 12" sch40 PVC and decided to make a couple enclosures. I also happened to pick up a bunch of 3/4" MDF at work.

I started by cutting the PVC to length. Then I traced circles onto the MDF. I cut out four circles of MDF and carefully sanded them until they were a light press-fit. Then I cut some rectangular pieces of MDF and used marine epoxy to laminate the circle to the rectangles.





Then I dressed the inside of the PVC with a 100-grit disc on my angle grinder.



I used some leftover West Systems epoxy from a boat project. This is expensive stuff, but extremely foolproof and very high quality.

I mixed up a batch and added cotton fibers until the consistency of peanut butter. I slathered it all along the circumference of the MDF disc and the inside of the PVC. Then I simply assembled the disc by squishing the PVC down over the MDF. THen I just filetted the extra epoxy. It has formed an extremely tenacious bond to the PVC.

Here is one tube assembled with my toolbox on it for weight until it cures.



I will then use a router to cut the MDF flush with the PVC leaving one side squared for feet.

More updates and photos as I progress.

Anybody recognize the manufacturers stamp on this??

thanks
Jeremy

I have a Millbank Talisman II amplifier, which is blowing its fuses.
It would be great if someone had a schematic, or an advide how to repair this kind of amplifiers.
This Talisman II amplifier is of the type Dynamic Loop System (DLS), and is constructed to feed a hearing aid loop in a meeting place.
The end stage transistors are 2 times 2N3055 and 2 times 2N3055H.
When the two fuses just after the rectifier/Elco's were blown, I replaced them with new ones.
After switching on, the amplifier became hot, smelled, and one of the fuses is blown again.
To fix this, I am looking for a schematic, or - even better - a repair manual for this kind of amplifiers.

I lost an OPT due to a bad valve and i didnt catch it in time.

So i either need a pair of OPTs, pp, for el84, UL tapped (preferably 25%)

Or a single hammond 1650 e

I am in the uk.

Thanks

Working on a 1 amp power transistor matcher.
It works around a transistor stage with base resistor and collector resistor with differential amplifiers measuring voltage across resistors.
From this it sends the plot to the pc via USB to display up to 5 different transistors at the same time.

A lot of buy in matchers are battery powered and often just use a couple of milliamps to measure the transistor.
This isnt a real world test as power transistors often work at amps rather than milli amps.
Most of the circuit is about generating a voltage ramp from a microcontroller then reading base and collector currents through differential amplifiers.
The microcontroller end is made as simple as possible and the heavy coding is done at the pc end.
You can zoom in on the 5 plots and run cursors along the plots to get Ic, Ib, Vc, Vb and Hfe at any point.

Owner stated this amp goes into protect. This is a Type 4 amp. It works until the amp draws about 15A from the bench. Input power voltage changes dont affect the outcome. When it pulls over this, the output waveform gets badly distorted and the amp also makes a slight buzzing sound. If pushed the amp will protect (DC offset?).

Any thoughts as to why the amp works <15A draw? Idles at 2A. Nothing shorted afaik.

Photo at terminals under load. 65hz sine wave.

WANTED TO BUY:

Looking for an excellent condition 12 inch: Jelco TK-850L MKII Tonearm, Ortofon TA-210, or Groovemaster I or III. Ideally boxed with all original accessories etc.

Sorry.. I mislabeled the heading.. looking for a Jelco TK-850L MKII.

Happy to consider alternate similar tonearms.

Happy to trade. Please see my available items here/diyaudio and US Audio Mart.

Thanks- Doug





Jelco TK-850L MKII Tonearm, Ortofon TA-210, or Groovemaster I or III.

I got four of these guys for cheap. They are probably designed for heavy duty thyristors with M20 stud mount. Dimensions are 70x80x100mm (base width x base length x height), the weight is about 800g. No specs of course. Can you estimate how mush power they can dissipate?

Hi All:
My Yamaha RX-V481 suffer the relay click sounds repeating issue.
Login to view embedded media
After open the case and comparing the service manual, the output stage relay is suspected.
But after I change the relay(RY221/RY223), the click sound repeating can't eliminate.
Have any one suffer the same failure problem?

B/R

For Sale:

4x universal regulator boards (https://www.diyaudio.com/community/threads/linear-regulator-pcb-lm317-lt1085-lm338-lt1083.254981/) - free! just pay the postage

SOLD 2x White SLB reg boards from XRK - £22 each
SOLD Mini-Me micro valve phono preamp board + 4 6N16P valves. (https://www.diyaudio.com/community/threads/mini-me-phono-preamp.242855/) This one was purchased from another member. There has been some work shown in the pictures - £25

1 Available 19v ACA kits I found in my cupboard! Each kit makes complete L&R channels. I only opened one for photographs.

Contains as per the listing (https://web.archive.org/web/2016031...products/amp-camp-amp-kit?variant=14849115012):

• Printed Circuit Boards
• Transistors including Linear Systems's JFET's and IRC MOSFET's
• Vishay/Dale Metal Film Resistors
• Elna Silmic ll and Panasonic Capacitors
• Bourns Potentiometers
• Rocker Switches and LED's
• Keratherm® insulators
• M3 board mounting standoffs, w/ bolts and washers
• Mounting bolts for Mosfets w/washers, high quality keratherm insulators
• Gold plated Speaker Terminals and RCA Jacks
• Power Connector Jacks
• Wire
• 2 laptop style power supplies suitable for the project

All you need to add is the heatsink/casework

Price reduction to £80

And why do we seldom see any results of bench testing of these?
Just curious from a guy who spent a lot of time in the lab.
And then 45 yrs selling test equipment to others.😀

I found this passive circuit online

http://web.archive.org/web/20070602004531/http://www.tkk.fi/Misc/Electronics/circuits/linesum.html

I need to connect the my left and right pre-out to my sub, the sub only has a single RCA inputs. If I use the circuit above, will it not affect the pre-out that goes to my main power amplifier powering the left and right speakers?

These are both Sovjet subminis.
2p5b / 2П5Б rod tube power pentode
6s6b / 6С6Б single triode mini
Any datasheet any language welcome.

So as I previously posted I found a Williamson 40/40 amp I cobbled together a LONG time ago, thanks again to everyone who contribute to that thread. So I gently woke the amp up, trimmed the bias to about 30 mA and hooked it to a set of Cambridge Soundworks Ensemble 3 speakers I found at a Goodwill for $40. I set it up in our bedroom, I'm driving it with an Amazon Echo Dot, and I cannot believe how nice it sounds... just so "sweet". The Ensemble 3 "subwoofer" doesn't have much reach so it's not great on hard rock but still it's a fun system to listen to folk music on.

The only downside to the system is that it won't play very loud because for reasons I can't recall I used a 24 VAC transformer so the DC rail is only about 32 V, this limits the output to about 7 W. So I'm thinking about building a true 40 W system with a 48 or 50 VAC transformer. One obstacle I'm facing is that the design is over 40 years old so most of the transistors are hard to get now, so I'm doing LTSpice simulations with parts with better availability. However no matter what I do I can't seem to get reasonable distortion results even with lots of output bias - about 90 mA static in the attached example.

Attached is my latest iteration. Some changes I've made:
#1. Changed output bias generator to Vbe multiplier for greater flexibility.
#2. Changed output transistors to FJA4313 and FJA4213 which are about the beefiest TO3P transistors I could find.
#3. Removed the output current limiting stage since the transistors look like they could withstand quite a bit of abuse.

The attached LTSpice simulation shows just under 0.5% THD at 1 kHz and 15 W output. There's a lot of odd harmonics in the FFT which made me think of crossover distortion but if you decrease the input to 50 mV pk-pk resulting in under 50 mW out, there's no visible crossover artifact. Also the distortion goes up to over 1% even though it appears to be in Class A.

I'm stumped as to the cause of the distortion, can anyone give any insight?

Thanks,

tommost

Hello I’m looking for Suggestions and electronic advice on starting this project.

The goal is to…

-trigger the four percussion sounds from the 1970’s drum machine Of the farfisa matador-r
using midi /relay interface from a Daw to create original drum patterns

-Add in a seperate audio line out for each four percussion sound so they can be Routed through individual effects in filters To a mixing desk for panning and eq adjustment.

I shall continue posting as The project progress please any advice would appreciated.
Thankyou

Recently acquired free box of tubes(pic)- Have another box full from young age tearing down old TV chasses...(plural??)
Want capability to eval before developing circuit for any of them, so think tester is wise 'maturing' hobby investment. Found article in link below informative:

https://www.radiolaguy.com/info/Mutual-Emission.htm

Decided on mutual conductance design, as I like the idea of introducing varying signal to the grid(s) instead of static voltage tests (emission)- if I understand it correctly ;<)
Also wanted capability to test later design (ie 60's) tubes and compactrons. So despite dizzying array of different makes and models- the Hickok 799 seemed to fit the venue. Also of interest the Weston 798-5B. Requirements moving forward were availability of good calibration and operations doc's, and houses for service if needed. The Hickok filled all of these, imo.

Would like to hear from those who have used these examples , and perhaps other rec's..
Thx,
Jim
ps. ordered this info to help w/ determining if the 799 has what I'm looking for
https://www.ebay.com/itm/122241588309

I did not realize that Metallized Capacitors ("Condensers") were developed by Bosch in Germany in WWII and taken-over by the US government.

Smaller, cheaper, for many reasons. Zinc is about the cheapest conductor. Zinc vapor is thinner than any foil we can wind. Just spray, no heavy rolling. Zinc vapor will burn-back at any defect in the paper, "self healing", over-rate your paper. Actual foil caps have become rare except atom-bombs and a few audiophiles.

I’ve had a lot of trouble finding transistors from the usual places and them not being fake, so I wanted 2SD669A & 2SB649A also 2SC3241 & 2SA1358, I decided to try Cricklewood I’ve used them many times especially in the late 70’s & 80’s and always been fine, but 2 of the transistors 2SD669A look like they are made by Hitachi as it has there good old logo on it, my question is has anyone used these transistors (which are not made like the good old days brass based tinned in silver that’s how I remember all the transistors like BD131 BD433 BD140 etc etc and many power it’s) and work fine I’m sure if you used them for low voltage low current switching they should be fine.
The amplifier voltage rails are +55 -55 so when they blow they go with a bang 110volt so fakes take off.
Here are the pictures

I recently got a Rane 6 channel amp. Testing it after unboxing, it seemed a little lifeless on the high end. So I did a quick FR measure (each channel measures identical) and it's down 3.5db at 20kHz, starting at about 6k. Spec is 20-20k with no db part mentioned. I verified my test setup using another SS amp which goes right out to 20k flat, then falls off.

I simplified the schematic to make it less of an eye candy. The input op-amp has a bandwidth limiting cap, but its spec says that rolls off starting at 50kHz...

It's understandable why they designed it that way, as it has to drive whatever a system installer can throw on its output. I promise to be more gentle with loading. Thank-you for any insight toward modification to change this aspect!

I have recently acquired a 1956 Montgomery Ward 3-Speaker Console (2 Jenson 8 in. Woofers and 1 Jenson 3.5 in. Tweeter) and am looking for a little information on the amplifier in the unit.
More specifically, I am attempting to locate the Dayton replacement capacitors, in order to bring a little life back into the old beast and get rid of the nasty buzz and heat associated with the leaky paper caps. Attached pictures are what I've got so far from the console.

I've been playing around with my 2 NAD 3020 Series 20 amps today. They've both been recapped and serviced and sound excellent, but both have a low volume hum on the right channel of the preamp that is not present on the power amp output. It's a bass frequency around 100 Hz that does not respond to the volume control but increases in volume with the bass control, as you might expect given the frequency.

This is a bit annoying to say the least despite the low volume of the hum. I do have sensitive hearing and now I've noticed it, I can't stop. I can make it go away by turning the balance dial all the way to the left channel or removing the pre-power links for the right channel. It would be nice if both channels of the preamp were as clean as each other. BOTH of my units are going this. I hope it isn't normal!

Any ideas what could be causing this? I replaced the 4 1N4002 rectifier diodes in one of the units without change.

F5 amp up for grabs. Nice condition looks new.

25Watt on DIYaudio F5v2.0 pcb.

£350.

I think the chassis and parts alone exceed this price.

Heavy piece of kit so collection only. Sorry.

Please excuse me if this is in the wrong section - Just joined the forums and am finding my way around.

I am working on a bunch of modifications to my KEF Q350s, including fully active crossover via DSP. One of the main issues with these speakers is two chassis resonances at 700hz and 1.2khz that I don't think I can fix with DSP as shown by this waterfall:





I have very little experience in dealing with such resonances physically - is there any "easy" way to reduce them, perhaps via polyfill or another damping material?

Thanks 🙂

Is this SMPS: https://connexelectronic.com/product/smps300re/
suitable for the Rodd Elliott P3A amp? https://sound-au.com/project3a.htm 60W class AB

I know SMPS have come a long ways but I can't shake the years of "look how big of a transformer this amp has" so I just want to verify that it will be fine for it.

thanks,

Has anyone compared Purifi vs. Ncore? Or even Ncore vs. Ice/Pascal/etc. ? What were the sonic differences, if any, and where (treble sophistication, bass, resolution, etc.)? Searchs aren't pulling anything up

I made a capsule microphone amplifier according to the circuit diagram circulated on the network

Working with 48V phantom power supply

But when I finish, it won't work properly?? The microphone has no sound

I don't know if there is something wrong with the circuit diagram. Please help me

Thank you.

Any chance anyone has a single Peerless DFM-2535R00-08 laying around - perhaps something they purchased for testing - that they would be willing to sell?