Orange PI PC + 3+3 watt amp power issues

[Peter Gregory]

I'm connecting my Orange PI PC 3.5mm jack to this power amp:

HiLetgo 5pcs PAM8403 2x 3W Mini Digital Power Amplifier Board AMP Class D 2.5-5V Input

If I connect a 5v 2a power supply to the amp and a 3a 5v power supply to the Orange PI PC, it sounds great with no noise form the Orange PI and no distortion from the amp power supply.

If I try to run the amp from the 5v pins on the Orange PI PC with the 3amp 5v supply, it will work, but there is a lot of noise from the main board and the amp does not get enough power to run properly.

Should 3a be enough to run both these peripherals?  I think the power amp will pull about 600ma, not sure what the Orange PI PC will pull.  I also want to connect a small 3.3v 2.8 inch LCD display to the board as well.

I think I'll need two supplies to make this work with no interference noise unless there is an isolation trick for the amp.  I also don't see wall pugs over 3a if I need more power.

Any suggestions?

 

 

[Werner]

The noise is probably picked up from the current that passes through the board from the power input to the pins. Also keep in mind powering peripherials from the board rather than a dedicated PSU is vulnerable to voltage drop and therefore may not work correctly. A slight overvoltage of something like .2 volts above 5V might be needed to compensate for latter but this won't fix the ripple voltage.

[Peter Gregory]

I've tried powering the hat from the header pins using the Orange PI PC board power, but that did not work well.  The board would reset when the amp would play.

I also tried connecting the power to the hat and powering the Orange PI PC from the header +5v pins, thinking that might help with the voltage drop, same result.

It really seems like the power amp + Orange PI PC draws more power than the 5v 3a supply can supply, or it drops the voltage too much.

I would think 3a could power the board & amp, but maybe not.  I'll hook a scope to it and see what's happening to the power levels.

 

Do I need isolation capacitors (0.1uf + 100k resistor to ground) on the audio output to remove positive voltage bias on the analog output?  Am I driving the amp always & draining power?

 

[Peter Gregory]

I finally got a configuration that works.  I got a 5v 4amp wall power supply to run the Orange PI PC

I connected my amp power to the 2 5v header pins and 2 and pins.

I connected the audio jack's L and R & common ground using the SMD pads instead of an audio plug (My plug was stereo and was shorting the video out to audio channels)

I put the audio signals through a audio isolation transformer to get rid of the ground loop current and filter out the big pop when the audio codec kicks on

That's it!

The 4a is strong enough to run the board and the amp without significant voltage drop on high power usage (~200ma draw from amp)

The isolation transformers eliminate the ground loop hum and chatter from the board operations.

The audio is clean and loud.