help with amplifier noise

[dookieshooter]

I've read a bunch of other posts about this, but I've not found a good solution yet...

I have a 2.1 amplifier connected to a PC via 3.5mm aux cable, running retropie. I am getting a low level hum when no audio is being output. I also have a USB volume controller that when change the volume, I hear some "noise" from as well. All the components are connected to the same power strip/surge suppressor.

I tried a usb audio adapter. Still has the same noise.

I tried a ground loop isolator in line with the 3.5 mm cable. The amplifier doesn't appear to detect the aux signal with this in line and thus no audio.

Tried a Line Output Converter. Same issue. The amplifier doesn't output any sound.

I have also tried an optical to analog converter. I know the converter works as I get output using a separate powered speaker. However, like with the ground loop isolator, the amplifier doesn't appear to detect the aux cable.

I'm guessing that the load isn't enough to trigger the amplifier to "think" the aux line is active in these two configurations.

I have disconnected all other power sources near the amp to eliminate the hum. No changes.

I have also tried a ground lift adapter for the PC to try and eliminate any ground loop issues. This made the hum much worse.

The amplifier has bluetooth in it, so I ordered a BT adapter (this pc is old) to try that out, but I'd rather not deal with BT issues.

I'm considering getting a different amp (this is my second one: https://www.amazon.com/gp/product/B08H1N7SSC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 ). I'm ok with going with a more expensive unit, but I want to keep it as small as possible.

Any suggestions on what I might be able to try next? Thanks for any suggestions!

[Lolonois]

I had the same issue with kodi (old pc) + amp, not related to Retropi. The only thing how I got rid of the ground loop humming was to use bluetooth (an usb dongle with aptx). I assume the very minimal audio offset and in maximum CD quality is acceptable for the retro games.

One additional thing you may try is to change the PSU of the PC, if applicable.
Does your PC has LED decoration (RGB stuff aso?), LED may also induce a humming.

For a Retropie on Raspberry Pi setup I was able to remove the humming by providing two PSU (one for the pi, one for the amp) instead of attaching amp and pi to a single PSU.

[dookieshooter]

@Lolonois I borrowed another smaller amp that I swapped in to test with. It didn't have any noise whatsoever. I'm chalking it up to a bad aux input/bad amp.

I also tried a laptop as the source... got no audio whatever.

That said, I did try using bluetooth, and that worked just fine. Like you said, sound quality isn't really an issue.

There are LEDs, but the second smaller amp did not exhibit the same hum/noise.

I'll try swapping PSU in a bit. The amp is powered off a wall adapter, so it's currently separate from the pc anyway.

[hoeveler]

@dookieshooter I don't have a lot of programming/code experience to help people here, but I do have a fair amount of audio expertise and this is a fairly simple issue to solve. It's called an "audio ground loop" and it's because the audio signal isn't grounded to the same ground as the rest of your components. Perhaps it's plugged into a different outlet or surge protector. The reason your second amp worked is because it probably has a ground loop filter built-in and the first one didn't. The easiest and cheapest way to minimize or get rid of the hum is to buy a Pyle PHE300 or similar device that (depending on the model) either connects to the signal that's going to the speakers or to the audio OUT from the Pi. It intercepts the signal and 'cleans' the hum from it by grounding the signal again.