Ground Loop Issue

[Hikaru12]

I recently relocated my PC to one side of my room and the monitor and periperals to the other side. This creates a nice organized modern look that I'm really digging right now. My issue is I've run into a ground loop. I'm connecting my speakers via the 3.5mm output on the back of the motherboard to them and modifying the sound with equalizer (sounds good to me, I use headphones with an external O2 DAC for critical listening). The problem is when the PC is turned off there's a huge loud hum from this. It gets worse as I turn the volume up on the speakers. I bought a cheap ground loop isolator but that only seems to silence the hum when the PC is on. Therefore, my question if I were to connect an extension cord from the speakers to the power strip where my PC is plugged into, will this solve the hum? Please see the diagram for more info. 

 

[anothertom]

How far are you running the signal over a stereo 3.5mm connection? As an unbalanced signal it is inherently susceptible to interference.

 

Having verything powered from the same socket will reduce chances of any ground-loop but you need everything to be properly grounded, including sockets. (Which isn't as common in the US)

[SSL]

If you break the audio connection with your computer, does the hum go away?

[Hikaru12]

On 6/15/2017 at 6:53 PM, SSL said:

If you break the audio connection with your computer, does the hum go away?

Yes it does. I actually ended up reworking my setup. I decided to bring up my stereo amp from storage and then plug in my O2 headphone amplifier for the lulz and it actually works as a really capable preamp. The hum still exists but the sound quality actually really improved. The funny thing is now I'm picking up radio signals as it's even more sensitive to this inteference.

 

On 6/15/2017 at 6:45 PM, anothertom said:

How far are you running the signal over a stereo 3.5mm connection? As an unbalanced signal it is inherently susceptible to interference.

 

Having verything powered from the same socket will reduce chances of any ground-loop but you need everything to be properly grounded, including sockets. (Which isn't as common in the US)

 

25ft signal. That probably makes sense as the longer it goes the worse it got. Do you recommend XLR connections to help with this? 

[anothertom]

13 hours ago, Hikaru12 said:

25ft signal. That probably makes sense as the longer it goes the worse it got. Do you recommend XLR connections to help with this? 

Over that distance i would definitely recommend using a balanced signal. There are a few ways to go about this, either a stereo DI box such as this (passive) one, a external sound card with balanced connections such as this, if you might want to record at a high quality in the future then an audio interface such as this, or if you want to do it on the cheap then a small powered mixer like this would do the trick.

[Hikaru12]

2 hours ago, anothertom said:

Over that distance i would definitely recommend using a balanced signal. There are a few ways to go about this, either a stereo DI box such as this (passive) one, a external sound card with balanced connections such as this, if you might want to record at a high quality in the future then an audio interface such as this, or if you want to do it on the cheap then a small powered mixer like this would do the trick.

What I'm doing now is I basically just connected my O2 with RCA to the speakers so it's by passing the noise floor with USB. No hum. I'm still running into faint RF interference coming from the RCA cables (15'). Do you think getting shielded RCA will fix that or is it worth investing in the linked mixer like you said?

[Marshnt]

The best and easiest solution it plug the speaker in to the same power strip as the computer with an extension cord.

[anothertom]

6 hours ago, Hikaru12 said:

What I'm doing now is I basically just connected my O2 with RCA to the speakers so it's by passing the noise floor with USB. No hum. I'm still running into faint RF interference coming from the RCA cables (15'). Do you think getting shielded RCA will fix that or is it worth investing in the linked mixer like you said?

Coming from live events, I don't believe in using unbalanced cables longer than 1m. Both from the interference rejection perspective as well as being able to run it any route I feel like without risking any power cables causing said interference.

 

Personally I'd go balanced over a long shielded run, as the cables and mixer will probably be cheaper than a highly shielded RCA cable worth using.