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I have the dreaded hum

I have a humming that occurs on one channel only. It happens when TT is off or on. When you swap TT leads it stays on same channel. When you swap interconnects from pre-amp to amp it switches channels. Only occurs when pre-amp is on phono input and set to moving coil. If you disconnect TT leads it stops. Equipment and set-up is all new. I've moved the equip around, no change.
I sent the pre-amp back to the dealer a while back and he said it was ok.
Today I bought a diff phono stage and the hum went away.
Dealer still thinks the pre-amp is ok.
What else could it be?
Tube amp and pre-amp
dirtbag
najo49
12 posts
 
Its your pre amp phono, MC section it need repair.Jan Olsen
sonicray
43 posts
 
I agree; that circuit is usually independent and thus is isolated as the problem. Don't let those reps jerk you around and good luck.
80stech
20 posts
 
Try a different set of interconnects
cerrot's avatar
cerrot
1,700 posts
 
Reconnect the old phonostage and see if the hum is gone.
dirtbag OP
17 posts
 
I tried a diff set of interconnects, no change.
The dealer is sending me another pre-amp to try, but he still thinks something else is causing it.
Could it be that the extra phono stage is isolating a ground loop?
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