ground loop isolator problems
hey guys, i've got the dreaded hum and have been reading heaps and trying to troubleshoot it the last couple of days.
It's a pretty lound hum, can hear easily over music, the main source seeming to come from the cpu fan. When i put my finger in the fan the hum changes pitch.
I've tried basically everything to fix it. I've basically grounded everything i can thing of to -ve straight from the battery with jumer leads. I've tried grounding the ground point on my m2-atx DC power suppy, the amp, the outer sheath of RCA leads. I've also tried grounding PC and AMP together, pc to rca, amp to rca, nothing decreasing the buzz.
Headphones from computer, there is no buzz, Ipod to amp, no buzz. Shorted RCA cable to amp, no buzz.
However when the PC is running off an external power supply and is isolated, the noise problems are gone, obviously indicating a ground loop and that both the PC and AMP are operating correctly right? What i can't understand is that grounding everything i can think of makes no noticable decrease in the noise!
ANYWAY, i did go out today and buy a $20 "car stereo line isolation transformer" today as most here recommend with these problems, assuming that this would fix my issues.
When it's plugged inline with my RCA from computer to amp, the volume is DRASTICALLY decreased to almost nothing. Boost the gain on my amp right up and the sound is obviously.....broken.
I CAN however ground the outer sheath of the rca going into the amp which brings the volume back up to normal. If i ground from the same point as the amp and pc's grounds, i get the same hum(not QUITE as loud though) as there's 88 Ohms from those grounds to battery (i know that's alot, but grounding either of them to battery still doesn't fix the problem!)
but if i ground straight from the battery the hum is almost inaudable.
My question is, are you SUPPOSED to have to ground the outer RCA connector after the ground loop isolator to get these things to work? isn't the whole idea that you DON'T have to do that, and just plug them inline? I'm going to buy a good heavy guage wire tomorrow and go a temporary fix from batt to ground the RCA, but that can't be the right way to do it can it?
I appologise for the length of the post but would appreciate anybody's input! I've read heaps of posts and the FAQ's on this forum but nobody seems to have the same ground loop isolator problems i do :(