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Class D Switching Power Amplifiers and Power D/A conversion

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Old 13th July 2009, 11:19 PM   #11
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thanks for the replies all
Jash, the 100nf caps are the small yellow ones closest to the top and bottom of the amp.

What do you mean by PCM and PVM conversion? I am not familiar with this. Shouldn't the amp just work with an MP3 player or computer audio plugged in??

I'll check the AC output and voltage input soon... the supply voltage is 24v but the problem happens with 12v input too I believe.
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Old 14th July 2009, 01:26 PM   #12
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sorry for the typographic error PVM is actually PWM

In fact the PCM 1808 converts the analog audio to serial audio format. then this serial audio is converted to PWM signals by TAS 5010
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Old 14th July 2009, 02:28 PM   #13
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audiomodder,

Jash was using the TPA3122D2 as a modulator for a TAS5261 power stage; he wasn't using it as a stand alone amplifier like you are. I think that's the cause of the confusion.
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Old 3rd August 2009, 05:35 PM   #14
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hey everyone,
sorry to report back so late, my last chip died so I had to order some new ones and redo a lot of the project.

I ordered new parts for every component all rated at 50v and ceramic this time to avoid polarity issues (not that I really had those before).

The amp still has the same problem BUT it only does this on 24v now, seems to run perfect on 12v.

The reason I found my chips kept blowing before is I had a bad 24v supply (I have 2) the bad one I am of course not using anymore. The bad one was somehow damaging the input caps but without making them blow(?) very strange. Anyway this problem is remedied and there is a new chip now but still clipping.

I measured the AC voltage on output at clipping and it's a little hard to grab since it oscillates extremely fast (<1sec) but I found that in normal operation AC voltage is usually <1volt, sometimes a tiny bit higher. When the clipping happens it jumps to 3.4v+ AC.

hopefully this info will be useful in finding the problem. I have 2 470uf caps close to the chip on the power lines, this should solve and power supply pumping problems (and I believe I tried more caps in the past as well). so I'm out of ideas. I took new pics of the board with the new components if anyone thinks that will help I will post those as well.

thanks,
audiomodder
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