Heavy interference/hum from speakers connected b/w computer and amp

#Cookie

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4
Hi all,

I have a set of speakers and a vintage amplifier which I've used with 2 of my computers. It's an old Rotel RA-412. I hook it up to either computer via a 3.5mm-Stereo RCA cable.
Whenever I do, I got horrible static interference. It makes more noise when the hard drives are spinning up, the processor is working, when I use the mouse scroller and so on- kinda like I'm hearing the computer working. This has happened with both computers. Both computers had sound cards built into the motherboard.
I've tried many different audio jacks to no avail.
Thing is, when I connect just an iPod I don't get any interference at all. If I plug the iPod into the PC to charge however (with the jack still connected to the iPod, not the computer), the interference comes back- even when the iPod isn't syncing.
I don't get this problem at all with headphones either, so it doesn't seem to be a mobo issue, and I'm assured this mobo is quality- it's a gigabyte GA-MA785GT-UD3H which has built in HD 7.1 sound.
Is this an issue with the amplifier, is it too old for the computer?

Thanks...
 
Ah - sounds like a good old ground loop. If you plug the amp into a socket on a separate ring main, does the problem still occur?
 
Hi- I'm at a college where my room only has 2 separate power points, so I assume they are both on the same ground main. I tried plugging the amp into the second ground main and leaving the rig plugged into the first, still have the same problem though... are there any other ways to eliminate this ground loop, assuming that is what it is?
 
Yup, they'll definitely both be on the same ring main.

Assuming it is a ground loop that's causing the problem, one of these beauties will see you straight. They're possibly the most used things in my box of audio tricks here.

One other thing to watch out for, however good your motherboard is the onboard sound will be, quite frankly, crap. You'll always get a bit of said interference just because of its nature - the solution is really just to buy a sound card and use that instead.
 
Thanks Berry- So a ground loop isolator should do the trick? I dunno if I'll get one quite that nice, I don't need an XLR or anything like that, just an RCA connector is all I'll need.
Cheers!
 
Assuming it is a ground loop that's causing the problem, one of these beauties will see you straight. They're possibly the most used things in my box of audio tricks here.

I had that box when I was having a slew of problems when I mixed professional and consumer products together. While it did reduce the hum, the problem still persisted. Ended up plugging everything into one outlet as the only solution.

By that time, I was out 50 bucks.
 
Just about every sound card I've heard does that. Most of the time though, you can only detect it with headphones or when the volume is super loud.
 
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