Dear forumers,

Does anyone even build something as a line array with a WG500 waveguide like PRV Audio has in their program?

B&C has a model that is a couple of inches smaller, model WG400.

I am obtaining to build a two way passive 8 inch cabinet style combined with this PRV Audio WG500 waveguide with 1,4 inch exit.

I was just wondering if somebody use them already.

I will post my build soon with pictures.

Greeting,

Pascal

Hey all, i am new to forum. I am trying yo build a passive box to sum 4 mono 3,5mm jack into 1 3,5mm jack . It all has potentiometer on each. Now;
Signal flowing on ch-1, but when i change other “empty” / “no signal flowing” channel’s pot the flowing channel’s level changes. Every channel has 2k resistor on middle leg of pot. Potentiometer’s are 10k value.
I know i will loose some signal. But need to figure that other resistor affecting system.
What to do?

Hello,

I am working on this Technics SP-15 from hell. It is trowing problems at me for a while now and the last one is again a special one.

After stop turning during a disc change a couple weeks ago, I have found a donor SL-1300MK2 and I had to replace both DN860 and AN640. Luckily the donor SL-1300MK2 had working parts.

Now that I've got it back spinning again, I see that it does not stop properly. Once I hit Start/Stop button with any of the speeds selected, it slows down but starts turning backwards and forwards a couple times before it comes to a complete halt. I should mention that, I have already performed all the necessary adjustments (the voltages, the current, the tracking) according to the service manual. The Brake pot seems to be fine.

As this very turntable was built in hell, the service manual does not include this problem in the trouble shooting section. Trying to outsmart the sadistic Technics engineers, I have downloaded the service manuals of other direct drive turntables i.e. SL-1200, SL-1300, etc and none of them mention such a behavior as if it shouldn't have happened.

I was wondering if anybody here has/had a tough luck like mine?

Best,
Dirk

Hello Guys recently I've acquired used Pathos Classic one MKIII amplifier and I'm very happy with it. However I'm little worried about the age of the amplifier as this model is produced back into 2007. I've opened the bottom case to inspect it visually but I'm not any expert on this staff. What worries me a brownish greasy material around some soldering but i don't know if i should use some kind of chemicals like deoxit to clean it. I would be very grateful if some one can take a look at the pictures i took and tell me if i need to visit electrician or to clean it up my self. Here is the link of the images ImageShack - Pathos Classic One MKIII

Thank you very much

Hi, just looking for some confirmation that my understanding is correct.

Say you have a 4 Ohm Woofer, 4 Ohm Mid, and 4 Ohm Tweeter

If creating Linkwitz-Riley crossovers for each component, you would calculate based on them being 4 Ohm.

Does that stay true if I then wire the Mid and Tweeter as series (8 Ohm), and then wire that to the woofer as parallel? Resulting in 2.67 Ohm?

Or, do I need to calculate the crossovers for the mid & tweeter as 8 ohm as they will be part of an 8 Ohm circuit before being tied into the woofer?

Thanks!

Hello

I got an idea today about using pc software to separate sound frequencies at a certain point then for testing using left and right channel for each frequencies group with a dual channel IC amp(TDA 7297).
I know I would have to lower the volume of the tweeter compared to the woofer and find the right spot, is there anything I have forgotten or maybe just don't know that I didn't mention ?
Edit: Could the difference in volume amplification be calculated based on the impedance difference of a tweeter and woofer or is it more complicated ?
Also would it cause some kind of distortion if the frequencies cut was a certain number (like 1000Hz so 999Hz goes to woofer but 1000Hz goes to tweeter) or does it need to be done gradually as to lower the volume on the woofer going beyond 1000Hz.

Is it better doing it this way compared to a passive crossover?

Thanks

I am finishing assembling the Lite Audio LS26 tube Preamp CAT SL-1 preamplifier and I needed some help in choosing the potentiometer.
At my disposal I have:

Alps Blue 50K
Alps Black Beauty 50K

any suggestions are welcome and consider replacement

At the moment given that I plan to use Alps Black Beauty, is it okay as a value?
Thanks 🙂

Hello everyone,
I desperately need some help. Does anybody have the copy of "Tele-tech/Electronic Industries" magazine july 1962 issue? I have downloaded this issue from americanradiohistory.com, but the main problem is that there is missing page from 115-118, 116 and 117 no pages are missing. That article is very important for my project and the main 2 pages that describing the circuit diagram are missing. So if anyone in this group luckily have the 1962 july issue of tele-tech/ Electronic Industries without a missing page, please let me know.The name of the article is"design information for regulating and stabilizing HV power supplies" by donald O. Ward.

Thank you all

too many amps, would like to sell these two boards, i would ship them only with the L-Bracket to save weight and space.

Asking 200,- Euros for both + shipping

Greetings!

I am a newb to DIY loudspeakers. I have been lurking in the forums, gathering info, and thinking about what kind of kit I'd like to start with for my first project. I recently picked up an old pair of Klipsch RF-3 II loudspeakers for $150 from craiglist, and the seller also sold me the matching center channel for an additional $40. I saw this as an opporunity to cut my teeth playing with something that could use some restoration and see how much I could improve them! I was actually sort of hoping something would be wrong with them so I could have a real opportunity to make improvements! 🙂

As soon as I got them home, I set them up in my HT system, recalibrated (with Audyssey, on my Integra HT receiver) and then put some music on. The sound was terribly harsh! It was just awful. I like a wide range of music, especially jazz, fusion, classical, and classic rock, and some of it I like to play pretty loud. However, the harshness of these speakers is so bad that I cannot play them as loud as I would sometimes like..

My internet search on the harshness and suggested modifications of Klipsch RF models revealed some facts about the horns on these products; namely, that they are known to sound harsh, and that some people dampen the horns to lower the resonant frequency such as what was done HERE. I also talked with a friend who has some Klipsch RF series in his HT, who informed me that yes, the Klipsch RF lines are in fact known to be harsh, but that they could also be revealing the harshness of my amp. He said he tried damping them with limited success, but also found that using a warmer amp (he suggested B&K or Rotel, and also that they sound particularly good with tubes) really made them sound much better.

But these sounded so bad, there must be something seriously wrong!

I decided I would try to refurbish them to see how good I could get them to sound and then maybe, try a warmer amplifier to see if I can hear a difference. My first attempt would be to damp the speakers similar to what they guy did in the link above. In addition to being able to possibly hear the difference, I always like to SEE the results of my efforts by measuring it. So I did a near field (about 1.5 inches from the baffle) measurment of both tweeters both before and after damping the horn. Boy was I in for a surprise! Both tweeters were almost identical in their response. Here is the result of one of them:


I was NOT expecting the huge suck-out at 8kHz! I did however, decide to proceed with damping the horns, just to see what it did. To that end, I found some rope caulk from Home Depot, and I thought I'd try it to see if it both was sticky enough to hold, while being easy enough to remove if I decided to change course. Here is what it looked like, in progress:



After re-installing the horns, I measured them again and the result was pretty amazing! Here is a screen shot of both a before and after response measurement of one of the tweeters:


Please note these are gated measurements using REW without any additional smoothing (as I don't have an anechoic chamber).

So this is encouraging.. The suck-out at 8kHz is gone! However, I see that while the lower range of the response was almost 20db higher than the higher end before damping, it is now almost 10db LOWER at the 3kHz area than it is from about 8-12kHz. This leads me to believe that the material I used is too heavy, providing too much damping? I would appreciate any thoughts or suggestions about this..

My next steps will probably be:

• Measure the overall response of the loudspeakers to get an idea of how well the crossovers are working
• Possibly rebuild the crossovers, as designed

I am thinking now that, since these speakers are almost 20 years old, it might be worth while to re-build the crossovers. Please let me know if, from your experience, this might be a worth-while effort. I have some questions about how to approach this that I will address in a new reply to this thread.

Any and all thoughts and suggestions will be much appreciated!

All the best,

Dave

Hello, I am currently a student in college and I am building a speaker as part of my project. I want to use a full range driver and I am looking to use Dayton Audio RS100-8 4". I want to make them passive too.

I am extremely knew to this industry and am quite intimidated by it all aha. I know I need other components but I am unsure to what. Could you please help me? Thank you.

I am trying to repair a Gemtune X1 amplifier. It had a burnt resistor on the board, I have replaced the blown resistor, but I have noticed there is no wiring coming from the live side of the power connector.

I am looking for a little insight as to where the live wire might connect in the system.

I guess I should start by saying I think I am over my head.😕 I'm not even sure if what I want to do is possible or worth it. If the answer is no to either just tell me and I'll stop right now.

I have two old subwoofers sitting in my garage doing nothing. I am intrigued by the idea of using them in my home theater system. Am I wrong in assuming that if I buy an amp made for home use that I can use it to power these? If I can, then whats the difference between a regular power amp and a subwoofer amp? The latter seems to be more expensive. But if all I need is the crossover, can't I just use the AVR?

Now for the subs. I know there are differing opinions on these, but I bought them when I was young. I've got two Volfenhag ZX-4712 DVC subs. I'd like to have them in two separate boxes; one on either side of the entertainment center. Possibly tuned differently if I go with ported boxes, or one sealed and one ported. I don't want to get into a complicated design.
Here's all the specs I could find on the subwoofers:
Volfenhag ZX-4712 DVC
4 ohm DVC
500 RMS
20Hz-1.1kHz freq. range
Fs 30Hz
Qts 0.526
Qes 0.614
Qms 7.698
Vas 56L
Xmax 16mm
SPL 89.58 dB
Sd 0.0491
Re 3.2 ohms
mount depth 160mm
mount dia. 282mm

I tried my hand at WinISD but quickly got lost. I entered all the values above but when I went to start a new project it says "Driver data fails integrity check". I added it anyway and started playing around. The EBP (if the values are correct) shows 48.9 which I understand to mean that either a sealed or ported box can be used. If I am looking at this right then the sealed box has a cutoff point at 37.66Hz, which is higher than I was hoping for.

If what I want to do is possible, would anyone be willing to help me figure out the best boxes to build? The outer width and length cannot exceed 20x22. The height can be as high as 28".

Thanks in advance!

So let's assume you have a direct coupled amplifier output, (in this case a Tim Mellow OTL) and you are looking to protect your speakers from DC on the output using a relay. Would you use the relay to (a) disconnect the output to the speaker or (b) use the relay to shunt the output to ground (leaving the speaker connected)?

I ask because I'm purchasing a set of PCBs from Ares for my Mellow OTL amp and the the soft start/speaker protection module has a large relay that appears to be in line, so disconnects the loudspeaker if DC appears on the output (I assume above a given small theshold - haven't actually got my hands on the PCBs yet so working from diagrams/pictures). That feels as though it's probably the safest but perhaps not optimal for sound quality and my inclination would be to shunt the output to ground in a fault condition.

Thoughts/comments?

Hi, I m looking for 2sk389v original jfet.

Please contact me on Gianluca.mazzoni85@gmail.com

Thanks a lot

I've got a philips cd371 with a cdm4/11, that is making a rather loud whirring mechanical noise when playing, from the unit. Musically fully functional, so it's a shame. Im new to this detail, so any info on which component is likely knackered and ideas on solutions gratefully received, thanks.

Hi guys,

I have this 3-way crossover + sub output, I thought to make an update of it by replacing all the opamps present, they are BA4560. My idea of ​​soldering dip8 sockets and so being able to insert and remove opamps. Do you think it's worth it? which opamp do you recommend affixed to the BA4560 type plug and play?
Thanks

I plan to order one today but, I could sure use some input on which one would probably perform the best. I mainly want it for music but, will use once in a while for a movie or two. All help will be appreciated and maybe I can get one ordered today. Thanks! 🙂
Klipsch SPL-150 800 watt 15" Powered Home Theater Subwoofer in Ebony 743878038644 | eBay

SVS PB-2000 Pro Subwoofer | 12-inch Driver | 550 Watts RMS

Hi,

-beginner writing here-

I have a set of speakers (see picture), with four KENFORD Typ PA300 8Ohm / 350 W / 96dB

(SPL 96 dB 1 W/m Diameter Voice Coils 63.5 mm, resonant frequency 38.5, Band Width: 48 Hz – 3 K Hz (-3 dB), re, 6.8 ohm, QMS 3.06, Qes 0,5654, Qts 0,4772, VAS 48 L, SD 0,0531 sqm, EBP.)

I'm also connecting two of these COMPRESSION DRIVER TITANIUM 60W
Skytec
Output power 60W
Magnet weight 13 oz
Voice coil 1.3"
Frequency Response 1.600 - 20.000 Hz
SPL @ 1W/1m 105dB
Impedance 8ohm


Could you recommend an amplifier that I could purchase?

My budget is quite on the low side...
Any suggestions welcome!

Many thanks!!
Alex

I am considering building cabinets for three 604C/D refurbed Altecs I have, and wanted to hear folks thoughts on sealed boxes. I recall that GM has suggested that they might work very well (with woofer/subwoofer support), but I believe his comments were in passing and not elaborated. My application her is a music oriented multichannel/HT room. I know they would be great in big MLTLs, but the smaller cabs will be easier to situate and offer more potential If I need to use them in smaller domestic rooms.

It looks like it might be difficult to go much below 2.5-3.0 cubic feet, so that's the size I'm looking at now. I've been using 605Bs in open baffles with 18" drivers in open back boxes below them for 10 years now, so I'm very comfortable with the duplexes and their crossovers.

This in advance,
Skip

I purchased this amp without thinking it all the way through. I have no Idea what it is... kind of looks like a Maggie of some kind. any help would be appreciated, schematics, model number, make. I don't even know tube layout. I know, I am an idiot, just ask my wife.

In laying out a crossover, I have studied the troelsgravesen information on inductor layout.

However, I have not read of any constraints on the routing of crossover wiring over, under, or around the open core coils. Are there any? I'm assuming any wiring close to or touching coils should be insulated.

I bough a korg nutube b1 preamplifier which has unbalanced output and I'm building an amplifier using icepower 200asc modules, which has a balanced input.

I've seen two ways of converting this unbalanced signal into balanced.

One: use Jensen JT-11P-1 line transformer
Two: use an RTX module (RCA -> XLR)

What are the benefits/which way should I go? My idea is to have both modules inside the same case.

I've got an elderly Marantz CD-48 CD player that is regularly struggling read a disc or will on occasion reject the disc partway through. I want to start with a good clean-up and hoping someone here can tell me what kind of screw driver I need to get these unusual (to me) screws out.
I suspect a recent development of distortion is also partially down to the player, though I'm pretty certain the caps on my amp need replacing.
Cheers all.

Hello !
today i am presenting you quite an interesting "issue".
On the last project i needed very big power transformers, and i have ended up with two big toroids of ~1500VA each.

I was noticing that when i have some house appliances turned on, the transformers began to hum very heavily.

i have connected an hall effect current sensor in series with the primary lead that goes to the wall-socket and i have captured some wafeworms.

oscilloscope is AC-coupled and the sensor outputs 40mv/A

This is when everything is turned of. Transformer is noiseless


this is with the hair dryier turned on on HALF-setting (i think they have used some sort of diode clamping trickeroo to get less heat/less air)

needless to say, in this situation transformers are humming very badly.

quite strange... isn't it ?
the voltage waveform is almost identical in both cases...

Any ideas ?

I've recently finished building the wooden chassis for my LM3886 monoblocks from the BrianGT kits, which have been almost 5 years in construction! (For convenience I've been using a lighter-weight Arcam integrated amp as I've moved multiple times since first building these.)



With no load connected, there is a very slight ground hum and almost inaudible hiss, however I believe both of these may be addressed by improved grounding strategy. At present I do not own a suitable pre-amp to drive the monoblocks, so I have been using the output of my Walkman A45 (24bit/96kHz DAC with headphone amplifier) - I understand this must present an impedance matching issue, however I've also noticed that using different 3.5mm to RCA cables can significantly worsen the hum issue - thus I believe the grounding strategy to be the main target. I'm also aware that the port proximity leaves a little to be desired, however I'd prefer to avoid altering the chassis if possible.



My questions are as follows:

1. As the chassis is insulated, might it be best to remove the AC Earth connection, and if so, where should the CHG (chassis ground) connection on the PCBs be connected to?
2. Are there differences that could be made in relating the RCA input ground (SG-signal ground) to the amplifier ground rails (PG- or PG+), for example connecting them directly, or any other changes that could be made in the amplifier to counteract the difference in hum between input cables?
3. As the amplifiers are monoblocks, I wish for them to reside close to the speakers. Is there a best-practice alternative to long (1m) single RCA cables (i.e. shielded, but not in a pair)? It's my understanding that RCAs are kept close to each other to minimise ground loops from http://hifisonix.com/wordpress/wp-content/uploads/2019/02/Ground-Loops.pdf
4. Do you have any recommendation threads for preamps/buffer circuits to allow hum-free connection to such a handheld player, or laptop DAC source?

I plan on building 2-way headphones, and want to cross the bass unit around 100hz with 24db or higher slope.

the easiest way to do so is using DSP but from what i understand DSP adds some delay, so my question is if that delay is even relevant to headphones case.
If it is, I would love to have recommendation for a variable active crossover.

cheers.

Class d chip amps have become very popular in both products, DIY kits as well as simple boards. Their sonic qualities too have improved with lower distortion and post filter feedback designs.

Will class D replace class A/B chipamps soon, some companies may just stop producing, leading to their death ?

Hi Guys
I wish to use this old car stereo mainly for its amplifier.
I have seen many "hacks" on you tube soldering directly in to the main board. Not keen.

Reviewing many threads in car audio made me realise the 8 pin Din connector was likely to give a CD player access (I originally presumed it was an output to an external amp).

From another thread's circuit diagram (a GM 120 - thank you) I have considered the pin assignments. i.e. 2 = GRND 3 = R in 4 = L in. See my photo. Correct me if I am wrong.

So, to use these inputs for an AUX connection, I can wire up a 8 pin Din and hey presto! Right?

Hmmm … I don't think its going to be that simple.

I imagine I need to do something with the other pins.

Can anyone comment and point me in the right direction?

Appreciate it

Cheers

Fud

Not sure which forum this goes into, it's Music, allright, but there's more people in the Lounge and someone might know something about promoting albums, I am drawing a blank here.

Just put a small collection of tunes up on Bandcamp:
Kaffi 101 | KaffiMann

And then I got a little bit more broke signing up on cdbaby so the stuff gets everywhere (eventually), just waiting for the pencil pushers to get around to it.

If I at least break even, I will consider putting up some more albums/tunes. Not counting on it though.

Does anyone have the ability/skill of getting people excited enough to buy music? I have lot's of other stuff going on with small kids, meetings of various kinds, emails, working overtime etc etc. The list is quite long really.
Is there some reasonably priced ad thing I can do?

And is it enough to pay diyaudio some sum so it might be ok to have a link in my sig? How does this work people? I am clueless!

Hi folks, I want to try with & without opt, only one tube per stereo, attached a couple of schematics & valve data sheet, I will try with & without feeedback, with opt & without opt capacitor. The opt is Edcor USA GXSE5-600-15K 5W 15K-600Ohms. I want advice what of the two schematics sounds better, also I need advice about the new B+ using the 15k-600 ohms opt target of Va is 90V.

TIA
Felipe

Dear all,

Is there any one know how to add an external clock to CS8414 ?
Many thanks.

Good day all,

I am a Mechanical Engineer by qualification, a Process Engineering Intern for the Remote Monitoring and Diagnostics Centre for a power utility and hardware/electronics hacker by hobby.

I have always been interested in sound. I used to do sound engineering for my whole school career, played enough instruments to know a bit and even assisted my brother with his car ICE sound offs. I have been limited by budget and experience but now plan to make some good solutions that I'm working and have learned a bit.

I have always loved guitar valvestate amps and had a Sony micro hi-fi with good speakers. I am planning to build a good amp for these 6Ohm Sony SS-H70 speakers. I also have an idea for a low powered system for off-the-grid sound (powered by USB from a battery bank).

I hope this forum can help me fill the gaps and get these projects online.

Keep safe.

A friend loaned me his Levinson ML-1 (John Curl JC-2) that had been sitting in a closet for years.

I plugged it in and noticed a 60 Hz hum but gave it a listen.

Unfortunately, I'm falling in love with this pre-amp but it's freaking ancient! The soundstage & separation of instruments is fantastic😱. I didn't know my speakers were that good.

I studied ME in school, not EE, but I assume the hum is because of an old capacitor? Any help on finding the device(s) causing the hum would be appreciated.

I know the modules are non-serviceable & pricey to replace assuming you can find them - so if a bad module is the problem, I get it.

If anyone has any advice or experience in what I'm facing, I'd be grateful.

Thanks,
Kevin Looker

Hi guys, I was just wondering if the two following amps are good for a diy 2.1 system. The specifications and the components seem to be overall good, aren't they?
Lusya 2pcs HI END L20 VER 10 Stero power amplifier finished board 200W 8R With angle aluminum D2 011|Amplifier| - AliExpress
Lusya Class D HiFi IRS2092 Power audio amplifier 600W*2 4ohm Stereo channel amplifier Assembled board + 60V B7 007|Amplifier| - AliExpress
Thanks
Ben

Hi all here are photos of a 6H6/717A converter I built recently. The 6H6 is parallel connected to the anode of the 717A. Filaments parallel also.

Having scratched the itch these are up for grabs .
In as new condition and perfect working order.
I will supply several different tubes with them.
The RA power cables are NOT included.
I will be listing my Counterpoint SA-3.1 preamp too once these have sold ,it sounds great with these .

These use pc88 tubes .
65 wpc into 8 ohms.
Input impedance: 60k ohm
Sensitivity: 0.7 volt rms for full output.

£500 + p&p
Please pm if interested

Hello all,

I am looking for a schematic of a Accuphase integrated amp, the E-206.
If the topology of this amp is similar to some of the other accuphase integrateds like E-203 E-202 E-205 and E-207, I'm also interested in those schematics.
I am asked to make an offer on a Accuphase amp which is broken, the seller says the fault is somewhere in the power amp section. He says the output was shorted, but I would think these amp are protected against these faults?
Anyways, what would you guys offer for such an amp? I would like to try and repair it, but with an amp of this complexity this could be a bigger bite than I can chew.

Regards,

Jarno.

Hey Anyone,

I opened up my ancient Snells to find what looks like clear lamp cord supplying the tweeters. Is there an optimal wire to connect the drivers to the crossover?

I am re-capping my vintage electronics' electrolytics. This consists of low-level to line-level circuitry operating on +/-18 volt rails. These particular capacitors are NOT in the audio path (I'll use bipolars for that), and used mostly as power supply bypass, ranging in values from 1µF to 1,000µF. I had already planned on sticking to 105c, 5,000 hr capacitors. Would there be any reliability improvement from using 50 volt-rated caps versus 35 volt-rated caps?

Hi guys,

I have a setup with 3 sources not diy (dac, pc, tv), going to a selector (just a simple rotary switch) and then to the amp (a diy TPA3251 with a 3e-audio board).

When i switch sources I get a loud thump. There are few mv of DC on the outputs of all sources, so I was wondering if I can do something at the amp input.

Cheers

Hi All.. new to posting but have been lurking for a while reading and trying to learn about Class D amps. I have a Behringer B1800D Sub with integrated 1400W class D.. Amp has failed and am trying to repair it. If any one has schematic.. that would be a lot of help.. but I have looked and looked and cant find any.
Anyway.. buy using what I have learned here and looking at tech reports and data sheets here is what I think it is.

Class D 1400 W..H bridge amp. using self modulation Delta Sigma
Uses IRS20955 gate drivers.. The Fets are IRFB4227;s
I measured +B and -B at about 78 volts. PSU is Behringer SMPSU28
Input and power stage are on Behringer pcb type P0981
I have included some pics of the amp and close ups for reference.

The Amp seemed to fail in steps.. My son said that the Protection light was coming on, but the sub was only putting out about half power. Then it continued to worsen to the point were it would not work at all. Power light would come on.. then Protection would flash and you would here a pop in the speaker, then it would just repeat this cycle. Eventually not even the power light woudl come on.

I unplugged the PSU connections to the P0981 pcb and all voltages seem ok. I did more digging and found both Fets on the B side shorted. Also after doing some resistance measuring and comparing from A side to B side. i determined the 20955 on the B side was toast as well..

Ok, so figured I had it nailed.. I replaced both 20955's with 20957's and replaced all 4 fets just because.

After doing this, I was able to power up the amp. Power light comes on then after a few seconds the Protection LED flashes and that cycle continues. So obviously something still wrong. I assume OC protection. I checked all voltages again at the 20957's everything seems to be where it should be. I watched the V(ds) on the fets with a scope and I see on the A side the High side fet is trying to turn on, voltage is at about 68vdc and drops down to about 30Vdc when the fet turns on for brief moment before the 20957 goes into protection.. On the B side.. I see again the High side fet turning on but the 68 Vcd drops to 0. So.. I think that there is some issue on the A side.. Fet is not turning on all the way or something as it should drop to close to 0 as well. In doing some checking all the sudden the amp stops the reset cycle. I just see the Protection led flash once at poweron.. CSD is charged to 10 V. I found now that VB to VS on the A side is only .8Vdc.. So I probably damaged the chip while trying to check it..and Vbs is not at 15V so chip is not starting up. I swapped the 20957's to confirm the issues moved with the chip. It did.. so I replaced the 20957. Now the amp powers up.. starts to cycle as before. I also noticed the there is just 4.5 vdc on pin 3 ( in) on the A side. and 3.5 on the B side. I measured resistance to gnd on pin 3 and on A side it is about 700K and on B side it is 212k.. so something not right there either.. anyway to make a long story short. i was doing some more testing.. Amp turned on and LIMIT let was on a long time and amp made a weird noise then power shut off and now the A side fets are toast and so is the 20957..UGH..

Sorry for the ramble, but wanted to give you as much info as I could..
Now to the questions.
1) do I have to have some signal at pin 3 ? all i was seeing there was dc voltages.. is this ok ? were does the self oscillation come from would a positive DC voltage here cause the 20957 to try to turn on the H side only thus causing the OC condidtion?

2) I was seeing about 10Vdc offset on VS .. is this normal ?

3) should the High side fet turn on first or the low side.. I read someplace the low side should to charge up Vbs but that seemed to be ok as the chip was turning on and trying to cycle on.

4) I think the OC reset was because the A side fet was not apparently turning on all the way..voltage across is should have been going to 0 i think right?

5) I included a pic of a chip I can't identify.. it is IC6 and has 8 pins It has H04 0'L on it.. I think this is part of the pwm circuit.. i was able to kind trace the singal flow from input to this chip. and I traced from this chip directly to pin 3 on both A and B sides.. I pulled this chip and then when I measure pin 3 to gnd both sides read about 700K ( before B side read 212 ohms) so I think this chip is also toast. I tried powering up the amp with this chip removed and it still did the OC thing and such and then that was when it toasted the A side fets.

Thanks for any input.. I know this is not really a DIY project but if know there are a lot of smart folk on here and thought I could get some advice.and help. I think im close.. but I dont quite understand what I should be seeing at pin 3 with no input signal and what the Fets should be doing at power on..

Hello.
Bought from Mouser 8 pcs. KEMET 470uF/450v. When opened the pack found two caps are not steady fitted in and have severe rattling inside the shell. I consider this sort of mechanical problem unacceptable and intend to return. But just as information , what can be the cause of this type of fault for a new caps please? The shell have not signs of mechanical shocks to suppose someone dropped to the floor , or some. These are first capacitors I saw rattling and was happened to be fresh new ones. Why ? Thanks.

Good morning,
I have 2 tpa3116 modules from different sources.
One has a Mute connector provided, but with no connecting info.
Another has a USB reader and no Mute



None will work. Outputs keep silent.
I know the Outputs are not GND connected and kept them well separated from Gnd.


Any idea what is wrong ? Are they so very fragile that they die at a mere glance ?


Pwer: 0-20V
input: from Generator or USB


Thanks a lot for your help !

I am tyna build a speaker with a Goldwood GW-8003/8 8" Full Range Driver w/Whizzer
how do i make it have AC power with trs input and volume control

just thought it would be cool to do this 🙂

Hello DIYAudio,

I have a set of Sony speakers (I think they're 150Wx6 Ohm each) from an old micro hi-fi. I wanted to build a Class D receiver/amplifier for them to use in my workshop. But I can't work out how to safely (and frankly cheaply for these cheap speakers) go about doing this.

The actual amplifier and filters etc. wasn't my problem. (I have in-depth "hacker level" experience with building circuits and working with chips etc.). But I a) didn't know if there were better or worse quality Class D Chips and b) couldn't work out what was the safest, most cost effective and best quality to choose between all the transformer stages with the power supply. For example, does an AC or DC power supply result in better sound quality with a TPA Class D chip.

My question is, what is the best way to use these speakers for less than $100? I can't justify spending more on them, but if that's too low please feel free to just tell me that I'm being overly optimistic.

I have no idea what I want the solution to be, I am just asking for a one line response or link from the DIYAudio pro's. It doesn't need to be Class D. It doesn't need to be a standalone receiver/amplifier but I didn't know if a "little" box on the back would be powerful enough. Giving them Bluetooth capabilities would be a great bonus, but yet again I just want to know if I can still use these speakers or should just bin them.

Thank for your advice!View attachment Sony SS-H701.pdf

FS: Transformer, used, not branded
Transformer Test shows:
Prim. 230 Volt, 50Hz
Sec. 36V idle, when loaded with 8A (4 Ohm) it drops to 33V

may be useful for such devices as shown here:
Retro Amp 50W Single Supply


price 25€
+shipping costs from Germany.

Those who have experience in output transformer winding, what would be the first textbook (if any exist) on subject that you would recommend to study from.


Thanks!

Hi

Newbie to this forum and looking forward to participating. Also hoping this is the place to get some advice about the feasibility of constructing a vintage amp?

Just for fun I'd like to have a go at building a 1954 Mullard design for a 5 valve 10 watt high quality amp (I believe affectionately known as the Mullard 5-10).

I have a copy of Mullard's construction booklet and there is also a quite detailed article on the amp on The National Valve Museum website (Mullard 5-10. Ten Watt Amplifier)

I have chosen this particular amp because I happen to have the booklet, but I have read on wikipedia (Mullard 5-10 - Wikipedia) that the circuit design was famous for its unique sound reproduction, so it will be interesting to find out.

The valves are no problem (EF86, ECC83, EL84 and GZ30), but I am concerned about the two transformers (mains and output). I doubt I will be able to get hold of original NOS ones so can someone help by advising me of a suitable modern alternative for each?

I have attached the relevant section of the booklet which refers to the transformers, the choice of which I understand depends upon loading. Three arrangements of the output stage are possible: normal loading, low loading and distributed loading. For want of any specific knowledge I guess it would be sensible to opt for normal loading.

Hope someone can help.

Probably a long shot, but I am after two second hand coaxial compression drivers. Let me know if you have anything 😉

I have a thought of frequency dependent load ( this is how a speaker with enclosure behaves.) simulation . This will help me to built cross over and see how this behaves. not only that but we will also help me generate wave file which I can run on actual speakers and measure performance and hear how likely would this final design would perform. this will highly eliminate the need of buying crossover components for every small change.

So I am looking for how do I incorporate frequency dependent load with LTspice if have impedance measurement file in csv format.

Thanks.

Hi all. I have this Heathkit AR-15 here, and it has had this symptom: One channel takes a good fifteen seconds to come fully alive. It moves from zero sound through distorted sound to full-on sound. But then at intervals it gets distorted again.
I think it has finally decided to die, though, because it will not come fully up out of distortion-land anymore.
It has this massive output capacitor, a 4000 mfd giant cylinder. Well, it HAD one; the previous owner (I am a recent Ebay buyer of this much-treasured receiver. At least by me) replaced it with a nice new one, I think Nakamichi? I can look up the brand but I've just put it all back together and don't feel like taking it back apart just now. The point is that it's been replaced so I am inclined to disregard it as the culprit. But I'm in over my head; I'm just an amateur; I do not know how to determine which component (because I'm not sure it's a capacitor, except that this problem tends to be due to a dying capacitor, from what I've heard).
I know it's advisable to do a complete re-cap, or at least it is for some people. For the moment, though, I'd like to isolate the culprit, replace it, and get back to listening.
I'm posting the schematic for the power amplifier section. I ran a test to make sure the problem is in the power amp (took the pre-amp output and ran it through another amplifier. It sounds OK).
Could somebody take a look at the circuit and tell me, in their opinion, which capacitor (assuming it is a capacitor) would be the one you'd suspect of having died?
Or what else could the problem be?
I'd really appreciate anybody further along in this hobby than me - I'm just a dilettante.

I've circled the electrolytics in the circuit on the schematic.

Thanks for any help.

Bob H.

I use Verizon Fios - the lowest tier (migation from DSL in 2017) service, and just as cheap.
But now, for some reason I've got blazing fast speeds!
(I did several "online speed tests" to confirm this)

I didn't upgrade anything, nor will I pay for something I didn't order.
Anybody got any ideas?

Looks fun!

https://sbacoustics.com/product/7½in-satori-coaxial/

Hello everyone,

I recently turned on my audio analyzer and it went right way to error 19 and no matter what I do (press clear. power off, etc.) it stays there. Any advise in how to clear the error? The manual I have is probably incomplete (only 147 pages) and does not provide much help. Thanks in advance for your help.

Felix

Hi guys,

let's see in your drawers, after your BIII, IIIse and your new Pro I think some poor BIIs, even 80Mhz ones, want to see some electrons flow through again.

Joke beside, if someone has a BII board and is willing to let it go for super cheap just tell me.

Thanks

Hey all,

Have a pair of Aleph-X PCBs.
Asking $40USD for the lot, plus postage from Australia

This topic has been brought up before in various versions, but here we go again...

So I have a bunch of 2-channel amplifier modules that I harvested from a Crestron CNAMPX-16x60. These are class AB 60W into 8R, 90W into 4R. In the amp there are 8, 2-ch modules for a total of 16 channels run from two large toroidal transformers. With the amp disassembled I am planning to use these in active speaker projects.

In one potential speaker system, I would like to use a 4 Ohm subwoofer but 90W is a little on the lean side in terms of the power requirement. So I am dreaming of using a pair of the 2-channel modules to create a bridged-parallel connection to the sub.

Just to get it out of the way, I understand about load sharing, gain mismatch, and DC offset issues. I will try to trim gain and match DC offset between channels, and was envisioning using series resistance on the order of 0.22R on the output of each channel. I will drive each pair of (+) and (-) channels using an audio interface with the (-) channels inverted.

This seems relatively straightforward, as long as some caution is used, however, I would be reassured by some practical and gentle positive feedback from the great minds of the forum. What sez ye? TIA.

Hi All,


I need more amp for some new speakers (100W, 91db/2.82V) and I'm thinking of foregoing my typical affinity for tube amps to try something different. I'd like to hit 100W at 4 ohms just to be sure I have maximum headroom for peaks but this is negotiable. The F5 is a nice easy build that gets me 40W at 4 ohms but I'm worried I will regret not maxing out my headroom. A turbo V1 gets me to my the target wattage but has more unknowns for me to deal with. So, I'm a bit torn between the ease of building a standard F5 and the potential complications of building an F5T (note that turbo boards are out of stock as of this post). I've read through the F5 and F5T docs several times and burned though hundreds of pages of posts and it's all sloshing around in my head so please help me get a few things clear:

• The F5 doc specs distortion at 40W into 4 ohms as .2% but does it clip there or is there a little more power albeit at a slightly higher distortion level?
• Can the 4U deluxe chassis from the store handle the dissipation of F5T V1 if I ever want to reuse or modify?
• Can the Linear Systems jfets in the store handle the higher rail voltages of the turbo without cascoding or is that reserved for Toshiba parts only (with some established risk)?
• Early in the turbo document, after suggesting the higher rail voltages in a standard F5 circuit, Mr. Pass says, "Want to drive 4 ohms with this? You can do it, but I recommend that you consider the upgrade to the F5 Turbo V1". I'm wondering what are the consequences of running 4 ohms at higher voltages - particularly if you are not pushing the volume most of the time.
• Would parallel output devices or reduced source resistors increase power into 4 ohms at all? I'm thinking not, but would like confirmation.

So, what you can probably ascertain from my questions is whether or not I can build a standard F5 today and keep a relatively short path to a turbo later, or if I can do something between a standard and turbo V1 now. For example, I could see myself hacking in a second set of output devices later without swapping out the boards, but adding cascodes not so much. Swapping out the transformer and filtering would be costly but easy, a new chassis not so much.


Sorry for the lengthy post but I've already spent several days running in circles and I find myself unable to pull the trigger on parts.


Brian

I'm getting a ground loop hum when the 12v trigger wire is connected between the preamp and power amp. I have ruled out everything source wise and tried an earth ground between the two components without success. If I remove the ground connection completely from the trigger wire gets rid of the hum and the trigger still works. I know running without a ground is not great solution if something should ever go wrong in the trigger circuits of either the preamp or amp.

Putting a 480ohm resister in series with the ground should still allow the circuit to complete but break the ground loop. Question is, is this better/worse than no ground at all?

I have a pair of F3 PCBs from Peter Daniel's run a while back. For some reason I thought I'll build 2 ...

$20US, plus postage from Australia?

Hey there,

I am planning to make a CRT oscilloscope to use on my audio projects. I am not an engineer but learning analog electronics... I would appreciate a lot if you could help me a little bit on building it. I am planning to make it from scratch.

I am willing to use a 3LO1I (3ЛО1И) tube
Here is the information I have found on the tube:



Right now I am trying to build the right power supply to power the tube. I will right here my process.

Thanks in advance...

Single. Please email me. Thank you!

Hello
I have been restoring my PS preamp 4.5 circa 1986. With all caps replaced, the constantly flipping of the PCB came with the output selector switch cap being unsnapped. The face-plate markings: On/Off, Straightwire, CD. Phone have 4 indents. I lost the ball bearing but retained the spring. I have located the ball-bearing size on line as well as direct replacement bu Lorlin. Problem is I do not know how to indent the switch to those output markings? There are 12 slots behind the blue covering. Also, There is a cap 2200uf 16V axial by the TIP transistor which originally is soldered to a bare wire bridge on the negative side and a PCB hole with no connection. May of been just a solder eyelet but with no connection? Is this so? Help.
Anthony

I want to make a switcher for digital audio signals (S/PDIF) that I can control from an Arduino.

I happen to have a stand-alone digital audio switcher so I thought I'd trace out that schematic and see how it works.

I'd appreciate some help understanding how this circuit works and why it is done this way?

The majority of this is pretty simple, the input obviously goes to a 74HC4052 (two of them, because this switches two independent outputs) which are high bandwidth analog switches. After switching the signal is fed to a 74HC04D which is a Hex inverter. Am I correct thinking this is simply to buffer the output?

The main bit I don't understand is why they have this resistor divider around the hex inverter. I can see they are chaining two sets of input/outputs in series to get back the 'non-inverted' signal, but why the resistors?? Can someone help here?

Thanks!

I made a reciprocating dirt sifter out of an old saw motor for my wife. The 24V power supply I had purchased off ebay to run my audio amp didnt work out, but it powers the pictured contraption at just the perfect speed. (Was using a Variac, set to "45")

We went to the nearby woods with the wheelbarrow this morning for some live organic dirt, in an attempt to inoculate a compost pile. Sifting out the roots, stones and leaves she found an arrowhead!

What are the chances?

Some time ago I planned to build a pair of Fonkens (http://www.planet10-hifi.com/) and here are some preliminary views.
Burch plywood is used and the results are very satisfying.
Still have to stuff them with damping material, screw in the speakers and wire them before I can listen.
I’ll report when done.

/Hugo

Hi there,

My CD85 has problems in the transport. Won't track further than track 1 or 2, sometimes 5.

Sometimes doesn't recognize disc at all, and sweeps the laser unit around at madness. Not a nice sound.

I have to find out what's wrong with it.

Can anyone help me finding a service manual for this baby?

A philips CD880 is almost similar, so this service manual would help as well.

Thanks,

Arjan

Hello Everyone,

I'm making an 4-way active open baffle, ww/w/m/t. My current issue is I plan on using two 12" woofers per side with a crossover of 200hz for the low end. I will be using DSP to control the crossover using FIR and phase/timing. Based off that, I'm confused as to how the sound waves interact with two woofers compared to a single one.

Do the sound waves multiple and act as one or are there other things to account for?

My plan is to time/phase align them to the rest of the drivers, but they are not going to be individually controlled but wired together.

Do I angle them to have mechanical time alignment or can I just dsp them as 1 speaker without having to angle both of them.

Hello, I am looking for a mid-woofer for a ported enclosure of about 11 litres net volume and have shortlisted the following 2 drivers:

(a) Scanspeak 15W/8531K00
(b) Hiquphon OW1

I have selected the 8531 (uncoated) version, over the 8530 (coated) one for two reasons:

1. I believe its lower Vas and higher Qt make it more suited to this small enclosure.
2. The response plot seems a bit smoother up to the rise that both exhibit between 1-2 kHz.

Having read lots of posts on here, the 8530 unit seems to be very highly regarded, although there seems to be much less written about the 8531 one. I also saw that the Carrera from Meniscus Audio uses the 8530 and OW1 combination but in a 15 litre cabinet.

Does anyone think the slightly earlier rise preceding breakup of the 8531 is the reason for it seemingly being less popular than the 8530?

If so, I see lots similar units from other manufacturers that go much higher before breakup. For example, the response plot for the SB Acoustics SB15MFC30-8 is level to almost 4 kHz although not quite as smooth as either of the Scanspeaks.

I also note that many of the other units cost a fraction of the Scanspeak ones!

Therefore, I would like to ask:

• Are these Scanspeak mid-woofers really “better” than their rangier competitors?
• If anyone thinks that my choice of the 8531 over the 8530 is flawed for this application.

Any help would be appreciated.
Many thanks.

PS I am very keen, have read quite widely and think I have grasped some basic theory, however, I have very little actual experience!

https://www.scan-speak.dk/datasheet/pdf/15w-8531k00.pdf
https://www.scan-speak.dk/datasheet/pdf/15w-8530k00.pdf
https://www.sbacoustics.com/index.php/products/midwoofers/mfc/5-sb15mfc30-8"

Hello,
want to build a PP pre with E80CC output tubes and have a plate to plate 10K Ohm, 600 Ohm secondary trannie. Have read some literature about calculation of the correct working point of the tubes for class A, but have some difficulties to understand the topic.

What I understood is, the correct primary impedance has to be calculated for the double idle current of one tube. So in fact, if one chooses 150V per tube and 4mA per leg of the trannie, than it should be 8mA for one leg and 150V. Result for this operatin point is 18K Ohms.

Could somebody please correct my calculation, if wrong.
Is there a possible class A working point for this tube that I could make use of with this 10K output trannie? Max. voltage of the power supply will be 300V, current is freely available.🙂

Hi everyone! This is my first thread in the forum. I am very happy to start a new part of my audio life. First repairing, and maybe one day building speakers.

You will quickly realise that I'm a newbie. The situation is the following: I got a 70's combo turntable, which sounded horrible. Thinking it was the reason, I exchanged it with a 80's Technics SL-DD33. It sounds way better! BUT... Now, because I have Sony STR GX-311 receiver which actually works, I realised that there's a problem with one of my loudspeakers. As the title says, the speakers are a couple of two-way Pioneer CS E320.

The problem I heard is that the right speaker sounded muffled, not as bright as the left one. When I changed the routing, I realised that's is not the receivers amp problem, but the speakers. Then I though "Muffled.. Not as bright.. It must be the tweeter.." So I ordered two Dynavox DX159 Tweeters. Today they arrived, and to my surprise, they didn't fit in the wholes (great..), and when I plugged them in, the muffled sound was still there! (great again..).

Now I think this is the project that I needed to finally learn how the whole signal flow from a speaker works, and be able to make some minor repairs. It seems to be a simple enough project to start with.

My questions are:

What would be a first approach to troubleshooting the speaker? I'm planning on making measurements with test tones. I will upload my results in the next days.

Is there a possibility that the muffled sound is caused by the crossover components?

I see that in the crossover there is a TOWA 63v 7uF capacitor, and there's what I believe 2 inductor coils (1.5 mh, and 0.26 mh??). Do this components age? And differently one amp from the other?

Can someone point me in the direction to a thread explaining how to measure drivers and with which software? Maybe the woofer is also working weirdly? It is a 20-716F .

Thank you in advanced.

Greetings,

I am looking for some advice on a project I am building. I have several knobs and switches attached to an enclosure, i have spent a few dollars on building the chassis, and will be coming to the point to adding the description of what each function.

Any advice on how to do this? Press on numbers?

All assembled and tested
Universal USB to I2S Interface Indicator PCB+Arduino Nano+OLED 1.3" include Isolator Si8065AA-B-IU
for Amanero Combo384-DIYINHK XMOS-JLSounds I2SoverUSB-Luckit WaveIO
more details :Universal USB to I2S Interface Indicator PCB | Dimdim's Blog
Price 40 euro

Most of us nowadays are using USB to I2S interfaces to "feed" our DACs with music. Most of these interfaces have a way of letting us know of the type of signal they are sending to the DAC (PCM or DSD) and the signal's sampling rate via supporting a number of LEDs, corresponding to the signal types and sampling rates.

A while back at avclub.gr I pitched the idea that we build a more universal sampling rate indicator, one that would display the sampling rate on a small screen and be compatible with most of the USB interfaces out there.

It would be open source, based on low cost Arduino hardware and be easy to build.

The Arduino would be galvanically isolated from the USB interface so as to minimise interference.

With these basic specs in mind, I proposed an Arduino Nano with an OLED 0.96" or 1.3" screen. I proceeded to write the relevant code, aiming to support most of the popular USB interfaces like the Amanero Combo384, the WaveIO, the DIYINHK XMOS based interfaces and the JLSounds I2SoverUSB interface.

Along the way it was decided to add support for basic IR control, such as power on/off and basic source selection.

This was the end result, still in the breadboard stage:



We decided to design a small PCB that would ease construction, since the isolators were QSOP-16 parts (only available at this footprint unfortunatelly). I did the circuit design and lemon did the PCB design work. We ended up with this circuit:



And this PCB:



This is the indicator in action, connected to an Amanero:

https://www.youtube.com/watch?v=Xxqe_1sWpkg

You can find the Arduino code at the bottom of the page, here: Universal USB to I2S Interface Indicator | Dimdim's Blog
(sorry - for some technical reason I can't give a working direct link to the file)

A lot more info (BoM etc.) on the circuit and PCB can be found here: Universal USB to I2S Interface Indicator PCB | Dimdim's Blog

It is relatively easy for me to support more USB interfaces, as long as they have the necessary I/O and documentation. I welcome requests. 🙂

I'm in the process of finalizing aspects of my computer desk amp project, chassis making, layout, bread boarding, etc. I'm now entertaining the thought of using DC for the pre-amp stage filaments (6J6) and have extra current to experiment/listen with trying the power tubes (6BX7) as DC vs AC.

I would like some advise on when to bother with regulating and when its not necessary.

I understand that with DH filaments there is a great advantage of using a regulator like the Coleman regulator. Because the filament IS the cathode and all that that implies.

But for tubes with separate cathode and filament would you put a premium on voltage regulation for the DC supply? Considering the extra space you need for an external heat sink and the extra current/voltage you'd need for the regulator cutoff, etc.

For non DH tubes, is a 1950's style RC filtered supply, except using the large uF capacitors now available (that were not available in 1950) good enough? Filaments prefer current regulation correct? Yet the many circuits I see use a simple voltage regulator, few and far between are current regulated as I peruse schematics.

In laying out my chassis (actually a wood/aluminum box, think 1960's tube table radio-like). I have an area reserved (2 inch by 4 inch) for the DC supply components/board inside. And I have an area on the back where I can hang a flat heat sink up to 4 x 5 inches. Which is quite a lot of heat sink! This is good because I want to use this same form factor for other projects, when I get out to the table saw I will probably make 4 of these cases for my next 4 projects.

So my dilemma is do I go regulated or un-regulated? Is the payoff for going regulated really worth it over a really good low ripple RC supply?

I can obtain a middle ground in DC current regulation (without using a regulator) by upping my filament voltage to maybe 9V DC and inserting a large resistor to bring it back down to the 6 volts. (that cost is heat not space). I have total flexibility on voltage because I have a space for a dedicated filament torroid, so I can buy any voltage of filament torroid I may need and just plop it down.

Thanks for weighing this, I want to learn how to do things not in absolutes, rules, or biases like "I always do this, or I always do that, just because".

Happy workers day next 01/05 for those who are workers and celebrate this day.

Meet Beepo: it is cheap and expendable yet robust, frugal but effective.

It mimics old-style tester like this one:



These electromechanical testers were quite effective and much loved, but they had a number of drawbacks: they were not very deterministic on the continuity threshold, and they happily passed 250mA or even more through the DUT, which is not very safe in modern, sensitive electronics.

This design (based on a previous version) keeps the advantages of the mechanical device like robustness, simplicity and absence of power switch but without the drawbacks: the current through the DUT is more than an order of magnitude smaller, it does not generate inductive spikes and is even faster:



The circuit is terminally simple, and looks like some lousy multivibrator but it shouldn't be dismissed too quickly: it does its job with a redoubtable efficacy: it works consistently from 0.9V to 2.0V (a single cell), consumes zero power when idle, responds instantly and has a deterministic resistance threshold of 3.5Ω.
It is also capable of almost magical feats, but more on that later.

The connection to be tested acts as a power switch, meaning an idle consumption limited to the leakage currents.
The circuit is simply an oscillator having a well-defined oscillation condition: (R5/R1)*(R2/(R7+Rtest))>1 (neglecting the dynamic resistances of active devices).

With the values shown and the parasitics, Rtest needs to be smaller than 3.5Ω (it can easily be modified).
Other than the resistors values, the circuit is extremely tolerant and will accept any type of semi and capacitor.
The capacitors determine the oscillation frequency (3.5kHz in this case) and can be altered to suit any preference.
It is reasonably well protected, and will survive a test of a charged capacitor (not at 325V though).
Thanks to its resistance discrimination and fast response, it is possible to test reliably and quickly multicore cables, large connectors, etc.
The supply source can be a NiMh, alkaline or saline cell: worn-out cells can be recycled because operation remains possible below 1V.
The cell can be soldered in place because the average current consumption is extremely low.
With a NiMh or NiCad element, the test terminals can work as a charging input thanks to the protection diodes.

Here are some pics of my prototype:

Dear all,
I'm Max from Paris, I'm a music lover and I try to get the best out of my not expensive hifi gear.
Thank you to you all for the huge amount of usefull information we can find in this forum.

Stay safe and wash your hands.

Max