2. amps-preamps
  3. 1432746902

Strange Hum from Right Pre Channel Only

My tube preamp has developed a peculiar hum problem only in the right channel, and it began only after I switched to XLR cables running from the preamp to the XLR inputs on my Krell FPB 300cx amp. I never had this problem when I used RCA’s from the pre into a RCA/XLR adaptor attached to the amp inputs.

Strangely, when I switch L/R channels for the XLR cables attached to the pre, the problem goes away, but now I have Left pre out to Right amp in, and Right pre out to Left amp in, not an optimal arrangement.

Please advise what could be causing this right channel hum and how I can remedy it, other than by reversing the channels on the pre end.

Thank you.

Neal
nglazer

Showing 4 responses by atmasphere

atmasphere's avatar
atmasphere
11,575 posts
 
An intermittent connection in the XLR cables sounds the most plausible from everything presented so far as Xti16 suggested.
atmasphere's avatar
atmasphere
11,575 posts
 
I've had it happen exactly that way a few times. Next time you have a problem, see if moving the cable at the input to the amp can make it come and go.
atmasphere's avatar
atmasphere
11,575 posts
 
Were you using the same XLR cables with the DAC as you were with the preamp?
atmasphere's avatar
atmasphere
11,575 posts
 
OK. Leave the cables connected at the preamplifier end.

Connect the other end of the cables to the amp. Do you get the hum?

If yes, swap the interconnect cables left for right **at the amplifier end only**. Did the hum move or stay put?
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