Ages ago I had some PCBs made and it's taken me an age to get them built up. In the meantime Richard revised the design, including the footprints for the off the shelf input trafos which I already had and would have been a hack to get them onto the green boards. And Richard having some semi pre populated boards I succumbed and bought some of the new ones. !
Looking forward to your findings. I use CapMx for my Class A amps and believe they work well since Class A amps have a constant current draw. Therefore I am a bit hesitant to use CapMx for this amp - no valid technical reasons. My TDA8932 mono block boards are lying on the bench - crying out to be built. But lately my work commitments are interfering with my hobby.
Hi and thanks. I have an Alpha Nirvana and ACA Mini incoming too...I must step away from new projects!
So got it on the bench....well the kitchen worktop. I played with my scope this afternoon.... learnt quite a bit. This SMPS is very low ripple. On the ACA with steady class A load of 1,5A it had about 15mv P-P and about 6mv of load. It makes a PwM noise with low or no load and it does this with the MonoAmps. Must be be much ripple going on . Haven't got the MJ filters in yet .
A few cursory measurements and I seem to have a lot more output on one channel. Fed 100Hz from my phone at full throttle, I have about 1,2v AC from one and 2.5 on the other.
What should I be looking for?
Dc seems good with shorted inputs I have 3.1mv and 7.5mv
So got it on the bench....well the kitchen worktop. I played with my scope this afternoon.... learnt quite a bit. This SMPS is very low ripple. On the ACA with steady class A load of 1,5A it had about 15mv P-P and about 6mv of load. It makes a PwM noise with low or no load and it does this with the MonoAmps. Must be be much ripple going on . Haven't got the MJ filters in yet .
A few cursory measurements and I seem to have a lot more output on one channel. Fed 100Hz from my phone at full throttle, I have about 1,2v AC from one and 2.5 on the other.
What should I be looking for?
Dc seems good with shorted inputs I have 3.1mv and 7.5mv
I seem to have a 'connection' between output POS and NEG on the channel with high output. Did a simple beep test and got a buzz over the speaker outs. I measure between 3 and 5ohms over the outputs +/-. Only when powered up...
Edit...that's a red herring. The 'high' channel is ok. The low one isn't right. Tried with music and a cheap speaker. Maybe my inductor track fix isn't so good afterall...it is on that channel. Although resistances are equal on both PBTL sides
Edit...that's a red herring. The 'high' channel is ok. The low one isn't right. Tried with music and a cheap speaker. Maybe my inductor track fix isn't so good afterall...it is on that channel. Although resistances are equal on both PBTL sides
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Seeing as one channel is roughly half of the other one then I'd be looking at the possibility that one half of the bridge on the 'low' channel isn't working somehow. Measuring the outputs relative to GND with a meter would show which but on AC Volts you might need a cap in series with your meter as DMMs generally don't much like DC superimposed on AC.
I've so far not had any problem when running them with no load attached. But then I don't put signals in normally without a load. You're keeping the amplitude small (1.25VRMS each side) I trust so that should be fine. I think the problem comes if the amp's asked to put out ultrasonics near the resonant frequency of the filter - then it looks like a short circuit.
So that was easy. Fed an arbitrary level of signal I had 52mv on 3 of the 4 outputs (stereo) but one on the bad board was well low. Was a dry joint on the big Coilcrafts. Playing music now on the main system. Yay!
Observations were I couldn't measure anything on the output resistors R13 and R14 and nothing on the input of L1/L2. I could only measure the AC signal on the out side of the coils. Is this due to the DC you mentioned and after the L the signal can 'see' the output caps and so my meter can give me a reading.?
All good though, time for a listen!
Observations were I couldn't measure anything on the output resistors R13 and R14 and nothing on the input of L1/L2. I could only measure the AC signal on the out side of the coils. Is this due to the DC you mentioned and after the L the signal can 'see' the output caps and so my meter can give me a reading.?
All good though, time for a listen!
Serious stuff Richard....wow . Impressed. Into my 'maybe not so easy' B&W DM14 sounding fantastic. Gain is strong so no need to crank too much. Through my Salas DCG3 with 3x gain.
We build a load of amps and keep saying to ourselves we don't need any more...I ought to sell some. I haven't sold any yet but the simplicity of a build like this does make you wonder what we're playing at! Well .....a hobby......that's what. So no, we won't stop building amps we don't need will we.?!
But what with the massively escalating energy bills in the UK, and I'm sure other countries, I do need to consider what powers my speakers , without compromising the sound.... hopefully!
This is an amp I can confidently say is a keeper and my other class D and chip amps will most likely be sold (3255 and 7293). The costly jobs to run will have their place for the odd occasions/winter! But the monoamp will be my main amp I'm sure.
To throw a couple of affordable SMPS (tracopower 100w) and the tiny monoamp boards together to create such a musical sound in an affordable to build and run, ina small package is truly impressive. I look forward to adding MJ filters and subsequently trying a traditional trafo/rectifier/cap type PSU ....will be an interesting exercise.
Richard thanks again.
Edit...and they've been belting out fairly loud now for over an hour and they're all cool as a cucumber. I think the amp ICs have cooled down now they're playing. Shunt regs warm but nothing else. Output coils cold.
We build a load of amps and keep saying to ourselves we don't need any more...I ought to sell some. I haven't sold any yet but the simplicity of a build like this does make you wonder what we're playing at! Well .....a hobby......that's what. So no, we won't stop building amps we don't need will we.?!
But what with the massively escalating energy bills in the UK, and I'm sure other countries, I do need to consider what powers my speakers , without compromising the sound.... hopefully!
This is an amp I can confidently say is a keeper and my other class D and chip amps will most likely be sold (3255 and 7293). The costly jobs to run will have their place for the odd occasions/winter! But the monoamp will be my main amp I'm sure.
To throw a couple of affordable SMPS (tracopower 100w) and the tiny monoamp boards together to create such a musical sound in an affordable to build and run, ina small package is truly impressive. I look forward to adding MJ filters and subsequently trying a traditional trafo/rectifier/cap type PSU ....will be an interesting exercise.
Richard thanks again.
Edit...and they've been belting out fairly loud now for over an hour and they're all cool as a cucumber. I think the amp ICs have cooled down now they're playing. Shunt regs warm but nothing else. Output coils cold.
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If your meter's good reading after the inductor but not before it can't be the DC which makes it barf. It would likely be the 360kHz full-rail PWM signal which floods the meter and that's what it sees prior to the inductors.
Glad to hear you're happy Jim and shipping out your older amps
Hi Elias,
Post #1 has the prices : https://www.diyaudio.com/community/...8932-25w-8r-mono-amp-kits.359193/post-6318454. To purchase built kits, add 200RMB per pair of amps. Kits still available yes.
Post #1 has the prices : https://www.diyaudio.com/community/...8932-25w-8r-mono-amp-kits.359193/post-6318454. To purchase built kits, add 200RMB per pair of amps. Kits still available yes.