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Hum- help needed

It's been very strange and I cannot think of a logical explanation.
It will require all your attention.
1. Two mono blocks plugged in. EVERYTING ELSE IS UNPLUGGED,
ICs disconnected- hum in the R channel (can be heard from
2-3 ft. away)
Hum in the L channel- order of magnitude lower, I would consider it "normal", can only be heard with the ear to the driver.
So I would think, it's not a ground loop (nothing else is plugged in, heard in R ch. only.
2. R Amp. moved to the L speaker (other amp unplugged altogether)- no hum.
L amp. (used to be quiet), connected to the same L speaker, with the same power cord- hum.
3. All tubes switched L to R- no difference.
4. R amp moved back to the R speaker (position, where it used to hum- no hum.
5. L amp (used to be quiet)- hums, no matter what.
To sum it-up:
I think it's not a ground loop (see #1),
It's not the amp.- (see # 2),
It's not a speaker- (see # 2),
It's not the tubes- (see # 3)

So, here is my question- what the hell is it?
maril555
maril555 OP
619 posts
 
Hum was gradually decreased after lifting the grounds, unplugging projector and finally was gone after d/c DVI cable.
I havent's restored the ground on power amps yet, will do it today.
There is no cable or sat. connected to projector, just a DVD player.
Two new lines are dedicated lines, also they installed
new deducated subpanel and all five(two existing dedicated lines plus two new ones and one for the projector) are connected to the subpanel on the same leg, and grounded at the same panel, connected to a deicated ground rod, separate from the house ground.
Again, I'm going to restore grounding with the DVI disconnected.
I understand, that dedicated lines are not necessarily a cure for the ground loop.
I have Granite Audio Ground Zero, that I'm going to use soon. I just have to make ground cables long enough to connect mono blocks.
maril555 OP
619 posts
 
Tvad,
Thanks for the info on CATV.
I have nothing, but a DVD connected to projector, but I do have a computer with the the cable internet connection and also a wireless router in the same room, not on the same AC circuit though.
Would that be a potential source of hum?, and how do I deal with it? CATV have some cable filters, are they needed in my case?
jea48
4,268 posts
 
connected to a dedicated ground rod, separate from the house ground.
I thought you said you hired a Licensed Electrician??
Danger Will Robinson!
.
Post removed 
maril555 OP
619 posts
 
Jea48,
Maybe I wasn't clear- new ground rod is connected to the house ground as well
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