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Amplifier Hum - Only Amp Connected

I have read many threads on here about various amplifier hum.

I recently bought a used tube amplifier.  When I connected the amp and turned it on, I immediately heard a hum from the mid-range driver of both speakers. The hum is audible even if the pre-amplifier is turned off/muted. In fact, I unplugged all interconnects from the amplifier and still heard a hum when the amp was on. I then unplugged the the interconnects and unplugged everything else in the room from the outlets (turntable, pre-amplifier, TV, and cable box), so that the only thing in the room connected to the wall was the amp. I still hear the hum from the speakers when it is only wall>power cord>amp>speaker cable>speaker.

This has to mean that it is a problem internal to the amp, correct?
jdpawnbroker

Showing 2 responses by gdnrbob

gdnrbob
4,496 posts
 
DC offset is a b***ch.
As I said, I am dealing with a similar issue.
First, I would get an electrician to go over the circuit. If possible make a clean run to your system. Replace outlets with hospital grade outlets-cheap upgrade.
And, at the very least, make sure the wires are properly installed. Sometimes the ground and neutral get mixed up, then all hell breaks loose. 

Bob
gdnrbob
4,496 posts
 
I am going through almost the same thing right now.
One question:
Are the speaker cables anywhere near the power cords?
If so, try moving them as far away as you can.
B
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