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Speaker Hum on my Quad 12L Active's

I have a simple set up in my home office and up until recently things have been fine, but recently my Quad's have developed this hum. They hum when I'm not playing any music, plus I test them and they hum when the RCA cables are connected to the speakers, but not to anything else. Not sure what that means.

I usually play music from my computer wirelessly to my Airport Express and then go from there with RCA's to my active speakers. Any thoughts?

Also, I've checked around the forums for this topic and none of the previous questions seemed to fit my situation. Would appreciate any expertise here.
bdogsquad
hifitime
715 posts
 
It doesn't sound like the speakers because both started at the
same time. Try the interconnects into a preamp,or even a walk man type cd player,any source with a volume control. Try it with the new source unplugged from the outlet too.That might show a ground loop problem. Besides the above mentioned,I don't have any other ideas.
bdogsquad OP
10 posts
 
When you say power cords, you're talking about the individual cords for the two speakers right? Currently, I have the Airport Express, the two speakers, a preamp and a turntable all plugged into a powerstrip in that's plugged into a wall socket across the room from where my computer is.
hifitime
715 posts
 
I think that's what he had in mind?If the plugs aren't polarized,try reversing one of them too.Just another thought.
loose
239 posts
 
odd question, but do you have a dimmer switch somewhere in the room? if so, look there as a potential issue.

just a thought.
shadorne's avatar
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shadorne
7,477 posts
 
It sounds like you have a ground loop because it happens when you connect the RCA cables.

One of the speakers may not be grounded properly at your power bar - when you connect the RCA you are connecting the grounds between the two speakers with your Y connector that goes to the Airport Express - a microamp current flow along the RCA ground wire (negative) can easily generate auidble hum.

Seriously you should look into getting XLR cables - I know the Airport does not support them but you could easily add a DAC/PRE with optical in and XLR out.
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