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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

Showing 3 responses by jea48

jea48
2,944 posts
 
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)
Ics disconnected. Amp and speaker totally isolated from other Amp?
>>>>>>>>>>>>>

2. R Amp. moved to the L speaker (other amp unplugged altogether)- no hum
#2. Test, was L speaker cable still attached to L speaker and then R Amp connected to (L speaker cable and L speaker?) (L speaker cable/L speaker, a constant test control unit)
>>>>>>>>>>>>

L amp. (used to be quiet), connected to the same L speaker, with the same power cord- hum.
Was L speaker cable still connected to L speaker?
In other words for your tests did you always keeps the speaker cables mated to the speakers they were originally connected to?.......
>>>>>>>>>>>>>>

L amp. (used to be quiet), connected to the same L speaker, with the same power cord- hum.
>>>>>>>>>>
Just a shot in the dark, Could it possibly be a cable impedance problem? A problem with a Speaker cable?

jea48
2,944 posts
 
Yesterday my electricians installed two new 20 A. lines for my mono blocks and fixed the two I already had- ground was not connected at all,

Did you tell the electrician to make sure all the circuits were fed from the same Line, leg, of the electrical panel?

Did the electrician install 2 new dedicated lines, not separate lines? Two Separate lines often share a common neutral.... Not good for an audio system connected together by ics....

Anyhow- connected the amps- strong ground loop noise.
A ground loop problem more than likely would have existed before, it was not showing up at the time because as you said the electrician said the outlets were not grounded. Grounds were lifted.

As Tvad asked in his last post,
Now that the DVI cable has been removed, have you restored the grounds?
Tvad
Try restoring all the safety equipment grounds with the DVI removed from the system, do you still have a ground loop hum?
jea48
2,944 posts
 
connected to a dedicated ground rod, separate from the house ground.
I thought you said you hired a Licensed Electrician??
Danger Will Robinson!
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