ok, now it's come to this as a summary

first, i have a normal run-of-the-mill computer with a 1212m, a rotel rb-1072 amp, a diy tube headphone amp (grounded), subwoofer (not grounded), and various other equipment that shouldn't need to be considered.

the audio coming out of my speakers were scrumptious, as was the audio out of my headphones, but something new happened: i hear a ground loop noise from my speakers. I unplugged everything except the computer and speaker amp, and ground loop noise is still there. i then connect speaker amp to ipod. no noise. i then connect headphone amp to computer. no noise.

now here's the kicker: i then plug the computer to BOTH speaker amp and headphone via Y cable (which i've always used). there is noise though both (speakers a lot louder than headphones). i turned off the speaker amp. there is same amount of noise through headphones. i UNPLUGGED speaker amp. no more noise.

so bottom line is that i think there could be a power supply issue on either the computer or speaker amp. and of course, the speaker amp is not earth grounded while the computer is. so... any ideas? and no, ground loop isolator for the audio did absolutely nothing.

thanks

It sounds like you need to run a separate ground wire from the computer chassis to the speaker amp chassis.

haha that's exactly it. thanks!

now i got one more thing, care for a quick and dirty explanation? i'm curious to know why i would need to ground a chassis that wasn't even designed to be grounded.

I also need to ground my PC chassis to my amp chassis (but in this case, my amp does have a knob where to connect the ground, as it has a phone input).

The reason this happens usually is because you don't have ground in your power plugs, or the amplifier one has only power and not ground line



May be of interest: http://en.wikipedia.org/wiki/Domestic_AC_p...ugs_and_sockets

The problem with an amplifier (or other component) with an ungrounded plug is that the AC power going into it induces a little bit of AC current into the chassis. Not enough to shock you, but enough to be conducted back through the signal cables to the computer, which IS grounded. Because it is conducted through the shield of the signal cables, it also affects the signal wire inside of the shield. When you added the separate ground wire, the bulk of the current was conducted through it and so the noise went away.

sorry, now there's some more. it's starting to do it again. this time it's a really light higher pitched buzzing. it's not really loud, just high pitched enough to annoy me. um... any more ideas? and why is it just cropping up now? oh yeah, it's the source is the rotel amp again

Is the noise present when the amplifier is turned off? Is it present when the amplifier is unplugged?

now it disappeared some again, but a tiny bit is still there... o.O it's, like, magical or something.

anyway, amplifier noise will disappear only if unplugged; it's still there when plugged in.

Are there any sources of line noise nearby, such things as fluorescent lights or a light dimmer?

there's a fluorescent light system in my room, although the problems still exist when turned off. and my audio equipment's plugged into a cheap line filter