Noisy Audio

[washed]

The current setup emits a lot of audible noise from the speakers when both the RPi and the amp are powered from the same power source. Observed first in the prototype using the Pololu 5V DCDC converter for powering the Pi. The following lists the steps performed to debug this issue thus far.

• Assumed the noise originates from the DCDC converter
  • inserted LC filter between DCDC converter and RPi => no change
  • powered pi from 5V rail of a clean lab power supply => no change
• Disconnected TRS audio cable between RPi and amp => no noise (but obviously no audio, either)
• Powering the RPi from a separate USB power supply, grounds probably disconnected (needs to be verified) => clean audio!

The last point indicates some issue with ground loops.

Next things to try:

• create star ground closer to the sound card/amp
• use shorter cables
• split grounds between sound card and amp
• check for ground loops in general

[washed]

Mostly fixed by using the differential inputs (in fake diff mode because of the single end source). Some background noise remains and what is probably current ripple when using the 5V DCDC converter. The latter should still be addressed for the MVP imo.

[tmh-alex]

There is the faintest background noise in my setup as well. I think it's really coming from the amp and I'm a bit . Would've expected better performance from such a circuit.

But let's stay grounded (pun intended), it's really not a problem at all.

[washed]

Yes I agree. Maybe after the MVP we could look for a lower power, lower noise alternative.

Meanwhile, give #16 a spin for a software approach to minimize experienced noise ;)