PC to amplifier - hum

surball

I have a PC that I connect to my amplifier. I do so in two ways, one is via hdmi, no problem.

The second way is using a standard 3.5 inch headphone jack. The reason I use this method is so that I can do multi-zone playback using my amplifier. The amplifier only supports multi-zone for inputs that are via phono connections.
The problem is that I get a crappy low humming noise from my speakers when I use this method. This happens in both zones that I have setup, when both used or just a single zone.

- I am using pretty decent 3.5 to phono cable to do this.
- I probably could and should have better cable management at the rear of my amp (but I dont think this is a factor - but its the next thing I will rule out)

What else can I try?

Is it worth trying to get a crappy USB external soundcard and see if that helps? You can get them from amazon for a fiver upwards.

Is there something I need to ground? I need to do this when using my record player on another system.

mossym

it's likely to be ground loop hum.

first, despite the fact many recommend it, and it works in a fashion, using headphone out as a line level output to a line level input on another devices is not ideal. the HP out is an amplified output, just not with a lot of power. if you have line out on your soundcard better to use that. there is a small, but unlikely chance that may solve your problem

using a usb soundcard almost certainly will fix it as you remove the ground loop. but the quality of the analog outs on a cheap soundcard may be very poor. i'd try and pick up a soundblaster with proper line outs at least.