@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.

@Swedishkiller12 Undervolting a 12V fan on the Pis 5V or even 3.3V pin is not going to give you any benefit. In fact it most likely is going to move a lower volume of air then your 5V fan on the 3.3V rail.

Fan noise really comes down to two things. Air turbulence (fan speed/fin design) and ball bearing quality/noise.

Spinning your fan slower and having an adequate passive cooler on the SOC is likely your best bet.

Have you measured/logged temperatures while under load? If you can do this while running on the 3.3V pin and are staying below the ideal max of 70C (this is not the absolute max, but rather the safe longterm max for most models) then you should be fine.