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Ground Loop Hum with balanced XLR cables only

I've been working to track down a ground loop/hum coming from my speakers. I've got an Integra DHC-9.9 connected via XLR cables to a BAT VT-6200 amplifier. I spent hours trying all sorts of things to eliminate and finally I swapped out the XLR cables for regular RCA unbalanced cables and voila the hum was gone.

Any ideas why this would be?

Thanks,
Nisi
nvlashi
dweller's avatar
dweller
3,779 posts
 
The three pins that make up the "XLR" are not always wired the same.
Consult the makers.
mofimadness's avatar
mofimadness
4,974 posts
 
One or all of the XLR cables might be wired wrong/different (pin wise) which would make the ground pin not connected correctly.

Usually it's the other way around. RCAs will create hum/noise and the XLR will solve it.
zd542
5,339 posts
 
Its probably because you’re running the amp balanced and the preamp SE. I've seen this type of hum several times. You may have to use the SE inputs on the amp. However, I've been able to fix the problem in the past with cables. Audioquest IC's with DBS was the cable that worked.
kijanki's avatar
kijanki
4,426 posts
 
Perhaps you have ground loop. RCA cables' shields are normally grounded on one side only, while XLR cables shields are grounded on both sides. It makes for better, shorter return of the noise induced currents but creates a lot of ground loop problems in recording studios that exclusively use XLR. I would try to connect together and to the earth ground all the chassis in star fashion (no daisy chaining) but I'm no "Hum Whisperer"
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