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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
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
Ag insider logo xs@2x
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.
samujohn's avatar
samujohn
291 posts
 
My 12L's never hummed as long as I used them with my stereo which was all located at the same end of the room. When I tried them in home theater plugged
in to the opposite end of the room from my receiver, they hummed loudly. I assumed it was because I had created a ground loop.
Hifitime offers a good suggestion. Try your inputs one at a time to try and find the loop.
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