Interference problem with PC and amplifier

neocon · 8 Feb 2014 at 16:18

I have my pc connected to a Pioneer amp and speakers. I can hear interference; like a hissing and beeping and it seems to worse with the monitor on (Qnix LED).

If I plug my nexus 4 into the amp , there is no interference what so ever. So I have deduced it's the PC that's causing this.

The connection between the PC and amplifier is a 3.5 mm to RCA tha I got for 99p.

(1.5m 3.5mm Jack to 2 x RCA).

Any ideas if a better 3.5 mm to RCA will rid my interference?

Tephnos · 8 Feb 2014 at 17:11

Well, a better cable should definitely help. Not sure if you'd get rid of it entirely without going with a balanced cable, however. Don't really connect directly into analogue with my PC however so I'm unsure beyond that. Is it onboard audio?

neocon · 8 Feb 2014 at 17:30

Tephnos said:
Well, a better cable should definitely help. Not sure if you'd get rid of it entirely without going with a balanced cable, however. Don't really connect directly into analogue with my PC however so I'm unsure beyond that. Is it onboard audio?

Yes, it's on-board (M4A785TD-V EVO).

Just been playing around. Plugged the amp into my other PC (Intel i5 3570k | Z77 DS3H) with different monitor and no interference noise.

Absolutely crystal clear on my nexus 4 with same 99p cable.

So definitely the PC/monitor (AMD X4 640 | M4A785TD-V EVO/U3S6).

Marsman · 8 Feb 2014 at 17:37

No, a better RCA cable won't make much difference in this case. It would help if the interference were being picked up by the cheap cable externally from other cables that it runs alongside, but the problem seems to be emanating from the PC itself. Sounds like a ground loop issue. You could try a ground loop isolator, see if that helps.

A well made RCA cable would be a good idea if you run the cable alongside other cables. Well made doesn't mean expensive though. You should be able to buy a decent cable and that isolator for under £10.

neocon · 8 Feb 2014 at 17:42

Marsman said:
No, a better RCA cable won't make much difference in this case. It would help if the interference were being picked up by the cheap cable externally from other cables that it runs alongside, but the problem seems to be emanating from the PC itself. Sounds like a ground loop issue. You could try a ground loop isolator, see if that helps.

A well made RCA cable would be a good idea if you run the cable alongside other cables. Well made doesn't mean expensive though. You should be able to buy a decent cable and that isolator for under £10.

Thanks, I may try one.

After more investigation it does appear to be the Qnix monitor power supply that causes most of the noise.

Marsman · 8 Feb 2014 at 18:24

Is it more noisy if the RCA cable is closer to it and less when moved away?

neocon · 8 Feb 2014 at 18:28

Marsman said:
Is it more noisy if the RCA cable is closer to it and less when moved away?

less noisy, i have tried to move the power brick as far away from amp and pc as I can.

I think it would good to get a digital amp and use optical connection between PC and amp, but I'll need to save up

Marsman · 8 Feb 2014 at 18:43

Well if it's the cable picking it up, get a decent RCA cable that is shielded. That's a good place to start, and if it isn't a ground loop issue, that may solve the problem.