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Hum building... ground loop?

835 Views 3 Replies 2 Participants Last post by  AV Doogie
I recently completed a remodel and moved all my gear back into home theater. The only added peice of equipment is a new NAD multi-room amp and speakers in kitchen - but all the elec wiring and speaker wire in wall etc is new.

I have a weird hum in that when I first turn the receiver on it is barely audible but it slowly builds over time until I turn the receiver off. Its in all speaker channels.

I've tried different outlets as well as unplugging different components in the theater.

Is this consistant with a ground loop problem - or does the slowly building aspect point to a different problem? I had ground loop issues when I plugged in my laptop to the receiver (I don't do that anymore) that I could never solve without a cheater plug but that hum started the instant the laptop was connected - not slowly building.


1 - 4 of 4 Posts
This does not sound consistent with typical ground loop interference. It is possible the new amplifier has an internal problem with a filter or amplifier feedback section.

Do you have a source (tuner DVD player) with a volume control which can be plugged directly into the new amplifier to see if you have an interaction with the output of your reciever and amplifier??
I should have mentioned the hum is in the speakers attached to the receiver, not to the new multi-room amp (I'll have to listen carefully to the multi-room in-ceiling speakers, but I don't recall them humming at all). Is it still possible that the new NAD amp is the issue?
Obviously, you need to isolate the source of the hum. Evidently, you did not have the same hum with the system operating in another location. Remove all components and cables from the reciever (except for speaker cables and speakers) and see if the hum remains. I would then switch in other source inputs to determine if the reciever emits the same hum during switching.
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