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The PAM8403 amplifier is very noisy

me_Cris

Hi!

I was thinking of participating in a challenge but I ran into another challenge. Sweat smile
I'm using a small circuit with PAM8403 as a replacement for some speakers with dead audio circuit. In addition, I also have addressable LEDs in the case (this how they came) and I was thinking of using an MCU to control them. But I just noticed a very sharp and annoying noise produced when I power the LEDs, and it doesn't go away even when playing music.
I made a msall PCB, the schematic is below. The power supply is at 5V [USB]. I placed some capacitors in the idea to support the supply voltage.
What ideas do you have? What could I improve? 

Thanks!

The schematic:

image

The layout:

image

PAM8403 module:


image
The initial amplifier + controller board:

image
image

The speakers:
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My assembly:

image

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  • It's difficult to completely remove noise when a lot is outside of your control; even some so-called hi-fi products get noise artifacts when things are interchanged in setups the manufacturer didn't expect.

    Are you sure you're not expecting too much; what is the noise level in comparison to the audio level, and what does the noise sound like? Could you record it?

    I happen to have one of those PAM8403 boards here, but I've never used it. I've buzzed out pin 8 which needs to be connected to a bypass capacitor according to the IC datasheet, and confirmed it's present, so the basic minimal circuit is at least implemented on that module.

    I will try to power it up sometime, but no guarantee I can do that this week. Not sure it would be all that useful to you anyway, since I don't have the same setup as you.

    If you can power-down everything else (LEDs/microcontroller), and remove the input (and maybe even short the inputs) then check to see if the noise is reduced a lot. Then try to add in the audio cables, and feed in audio from something completely separate and battery-powered to begin with, such as a portable MP3 player. Just take baby steps, and see what affects the noise.

    I suspect that you may eventually reach a point where the noise is low, but still noticeably there, unless you're prepared to change things a lot, e.g. say switch from USB power to battery, or not use the LEDs/microcontroller if not required, and so on.

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  • It's difficult to completely remove noise when a lot is outside of your control; even some so-called hi-fi products get noise artifacts when things are interchanged in setups the manufacturer didn't expect.

    Are you sure you're not expecting too much; what is the noise level in comparison to the audio level, and what does the noise sound like? Could you record it?

    I happen to have one of those PAM8403 boards here, but I've never used it. I've buzzed out pin 8 which needs to be connected to a bypass capacitor according to the IC datasheet, and confirmed it's present, so the basic minimal circuit is at least implemented on that module.

    I will try to power it up sometime, but no guarantee I can do that this week. Not sure it would be all that useful to you anyway, since I don't have the same setup as you.

    If you can power-down everything else (LEDs/microcontroller), and remove the input (and maybe even short the inputs) then check to see if the noise is reduced a lot. Then try to add in the audio cables, and feed in audio from something completely separate and battery-powered to begin with, such as a portable MP3 player. Just take baby steps, and see what affects the noise.

    I suspect that you may eventually reach a point where the noise is low, but still noticeably there, unless you're prepared to change things a lot, e.g. say switch from USB power to battery, or not use the LEDs/microcontroller if not required, and so on.

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