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Audire Diffet 1 hum

My Audire Diffet 1 preamp recently developed a hum audible through the speakers. Still sounds very good at volume, but probably like all of you, it bothers me. Could it be a transformer, capacitor or otherwise?

PS Audio had a nice article on isolating a hum, but didn’t mention the possibility of equipment. I guess my question is it probable that the problem is external to the preamp, like interconnects, or line voltage? (My other system doesn’t have a hum).  Oh, and it produces a thump when the amp and preamp are turned off together (I don't do this anymore).
128x128ballyroebuck
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ballyroebuck's avatar
ballyroebuck OP
12 posts
 
Great information Elizabeth.  Thank you and I'll give your recommendations a try.  Even with the hum, it is a sweet sounding preamplifier, so I wan't to keep it in use.
jea48
4,524 posts
 
Jmho, it’s not DC offset on the AC mains. I agree it could be a ground loop hum.

For a test disconnect all source equipment interconnects from the inputs of the preamp. If you have a sub also disconnect any interconnect/s from the preamp.

Plug the preamp and power amp directly into the same AC wall duplex outlet.

Check for the hum and post back your results.
Oh, and it produces a thump when the amp and preamp are turned off together (I don't do this anymore).

That's not unusual. 

Amp off first wait about 45 to 60 seconds then shut off the preamp. If you still hear a slight thump wait a little longer after shutting off the amp before you shut off the preamp.
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ballyroebuck's avatar
ballyroebuck OP
12 posts
 
Plugged into the same outlet:

I disconnected the only input, a CD player, and the hum is present, at the same level.. 

I also tried disconnecting the preamplifier to check the amplifier. The Audire Model 2 is quiet, no hum. 
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