I used this little amplifier (TDA8932 from aliexpress) few times in the past, but only as mono for one speaker. There were no problems and it worked great, both with battery and PSU.
Never tried to use two boards to create stereo amplifier.
Now, I connected everything, used shielded cable from 3.5 mm input port to the potentiometer (A10K). Connected left channel to one board and right channel to the other board, input minus is the same for both. Using one laptop PSU to power both boards (19V 3.4A). Everything works and should be connected properly.
My problem is that I get high pitched noise from speakers. I tried disconnecting power from one of the boards and after that the other board works fine, no noise.
Is there something that I'm missing or this is normal behavior?
Please excuse me if I didn't describe it correctly, my knowledge on this is very limited.
Never tried to use two boards to create stereo amplifier.
Now, I connected everything, used shielded cable from 3.5 mm input port to the potentiometer (A10K). Connected left channel to one board and right channel to the other board, input minus is the same for both. Using one laptop PSU to power both boards (19V 3.4A). Everything works and should be connected properly.
My problem is that I get high pitched noise from speakers. I tried disconnecting power from one of the boards and after that the other board works fine, no noise.
Is there something that I'm missing or this is normal behavior?
Please excuse me if I didn't describe it correctly, my knowledge on this is very limited.
Some class D chips do not like to be connected to the same power supply ...
for some cards under the pcb, such as 3e Audio cards may have resolved the problem whith modification under the pcb
Go to the chip manufacturer's website, this must be explained.
for some cards under the pcb, such as 3e Audio cards may have resolved the problem whith modification under the pcb
Go to the chip manufacturer's website, this must be explained.
I have to wonder if running the power wires and the speakers wires so close might cause some noise issues. It's good that they are perpendicular, but it might be better to avoid them crossing each other and keep them as far away from each other as possible. The AC input is pretty close to the speaker terminals too. Not sure if that will matter, but power, especially AC, can cause noise issues.
Just my initial thoughts,
Mike
Just my initial thoughts,
Mike
hi, you need to do the slave/master wiring. the same problem i had.
https://www.diyaudio.com/community/...essimistic-review.277130/page-38#post-6591937 look at post #749
https://www.diyaudio.com/community/...essimistic-review.277130/page-38#post-6591937 look at post #749
a couple of things you can try
1 use a Y connection for the power supply + and - connection instead of a daisy chain.
2 its not uncommon when using more than 1 class D amplifier in a chassis for beat frequencies to happen. The switching frequency on each amplifier is not exactly the same and the 2 frequencies will mix and cause a sum and difference to appear in your circuits. There is a Master and slave setting for the TDA 8932 chip for this very reason. There is also a 3rd frequency from the SMPS power supply that also is in the mix. You will have to look at the data sheet for the TDA8932 on how to implement master and slave.
1 use a Y connection for the power supply + and - connection instead of a daisy chain.
2 its not uncommon when using more than 1 class D amplifier in a chassis for beat frequencies to happen. The switching frequency on each amplifier is not exactly the same and the 2 frequencies will mix and cause a sum and difference to appear in your circuits. There is a Master and slave setting for the TDA 8932 chip for this very reason. There is also a 3rd frequency from the SMPS power supply that also is in the mix. You will have to look at the data sheet for the TDA8932 on how to implement master and slave.
Thank you all for quick responses.
I will investigate more on this master-slave system, assumed there is something like this but now I know.
Some other thoughts, case is 3D printed plastic so no shielding to attach the ground. I'm aware that AC is close to everything else, not sure how to separate it without doubling the size of the enclosure. DC input wires could be routed differently, but somewhere it would cross speaker output wires. I'll try to optimize that. Regarding Y connection for PSU, didn't thought that could be a problem with these low power amps.
Cable from input to the potentiometer is shielded, but not from the potentiometer to the board. Not sure if I could make something like this on such small distance. Maybe adding some kind of metal shield encapsulating potentiometer and wires.
Not looking for anything extraordinary, after all these are just couple of dollars boards. But they sound nice, just to get rid of that high pitch noise.
I will investigate more on this master-slave system, assumed there is something like this but now I know.
Some other thoughts, case is 3D printed plastic so no shielding to attach the ground. I'm aware that AC is close to everything else, not sure how to separate it without doubling the size of the enclosure. DC input wires could be routed differently, but somewhere it would cross speaker output wires. I'll try to optimize that. Regarding Y connection for PSU, didn't thought that could be a problem with these low power amps.
Cable from input to the potentiometer is shielded, but not from the potentiometer to the board. Not sure if I could make something like this on such small distance. Maybe adding some kind of metal shield encapsulating potentiometer and wires.
Not looking for anything extraordinary, after all these are just couple of dollars boards. But they sound nice, just to get rid of that high pitch noise.
I did connect Vssd(hw) with OSCREF for slave board. Also connected OSCIO pins to synchronize them. When I put 39k resistor between Vssd(hw) and OSCREF for master board, I get no sound, checked connections there are no problems. When I remove the resistor it works, looks like its not mandatory.
Still after that, there is high pitch noise, but I think this time it's from PSU, it sounds better but still irritating.
I disconnected PSU and connected battery...no problems, sound is clear and no noise in idle.
Does anyone have tips what should I do to tackle this problem?
Still after that, there is high pitch noise, but I think this time it's from PSU, it sounds better but still irritating.
I disconnected PSU and connected battery...no problems, sound is clear and no noise in idle.
Does anyone have tips what should I do to tackle this problem?
Try a Pi filter between the power supply and the amplifier boards. Ie CLC small cap inductor small cap. 0.1 10uh 0.1 cap.
@multisync Thank you for this tip, I didn't have a clue what is a Pi filter.
After some research, it was really simple so I decided to try. Wasn't sure what is "0.1 cap", suppose uF?
Anyway, I had 33 uh inductor and 470 uF electrolytic caps. It does the job 🙂 no more high pitch noise.
I could buy values you mentioned and try it, my inductor is too small but enough for a quick test.
After some research, it was really simple so I decided to try. Wasn't sure what is "0.1 cap", suppose uF?
Anyway, I had 33 uh inductor and 470 uF electrolytic caps. It does the job 🙂 no more high pitch noise.
I could buy values you mentioned and try it, my inductor is too small but enough for a quick test.