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Audio amp output volume become lower or quiet.

Dear All,

My audio output sometimes has no output.

The situation is :

  1. The output volume become lower. ( but I didn't change VR yet ), sometimes I re-plug power, it become normal again.
  2. The output volume become quiet.

The circuit is no change, the different is only plug power time, I debut the poewr AMP too hot, and lost its operation point. ( but I am not sure )

I remember that when I was 17, I bought a audio amplifier, the boss told me, when you are going to power on amplifier, remember to change volume to lowest first, or may hurt the amp. I didn't do that too much, about 5 years later, the amp become the situation as my audio circuit now - volume become lower or quiet sometimes.

Could you please advice ? Thank you very much.

Best regards, Boki.

Reply to
Boki
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Boki =E5=AF=AB=E9=81=93=EF=BC=9A

Hi All,

Sorry, "plug power time" that I means "power on time".

Thanks. Boki.

Reply to
Boki

So, you think the power amp *may * be overheating ? It might be 'thermal shutdown'.

More likely hurt the speaker actually. It's the trouble with non dc-coupled ampliifers.

What's the amplifier chip ?

Graham

Reply to
Eeyore

Eeyore =E5=AF=AB=E9=81=93=EF=BC=9A

Today, I am testing it without housing. Now I think it may not this problem.

ed

My circuit that extends the original PCB.

The original PCB has AV output for audio.

The original circuit is:

pcm1742ke -> lmc6482aim -> Audio output jack.

Now:

pcm1742ke -> lmc6482aim -> LM386 -> Speaker. (The original audio jack keep there, no cut )

The problem now is:

The audio is quiet in the most time, if I adjust the VR ( variable resistor ), sometimes ( about 10% ) the speaker will output audio abruptly.

If I volume down by VR slowly, and then volume up, the problem come again, very low volume.

Best regards, Boki.

Reply to
Boki

Ok.

Have you checked the LMC6482 output at the same time ? I assume it's OK ?

I don't recommend the LM386 btw. It's ancient and not really very good. Are you using low supply voltages too ? I'm sure it's not suitable for that.

Consider some of the TI PWM ( Class-D ) ampliifers that are intended for low voltage operation, they're obviously much more efficient too.

What's your output power spec ?

Graham

Reply to
Eeyore

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