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Turntable/Subwoofer Ground loop

I have a Rel B1 that is hooked up to Cary MB500 monoblocks via the high level connections.

I am starting to get a ground loop hum from the sub when I play a record. Only when the needle hits the record does it start. I have re-checked all connections, what could it be?

All the ground wires are connected what I think is correctly, but the high level connection from the amps to the sub has the wires stretched quit a bit to reach the amps and the ground.

Should I ground the Sub connection to somthing different, like the rack???
macdadtexas
tonywinsc
583 posts
 
That's correct. just a quick way to see if the feedback is mechanical. most subs have a phase switch.
macdadtexas OP
1,794 posts
 
Sorry, I meant sub, I did that, but there is still some hum.
macdadtexas OP
1,794 posts
 
Humming more again after some improvent. Only from the high level input. When that is disconnected, no hum, and no hum from any other componenet, or when playing anything except the turntable???
mwoh419
54 posts
 
You didn't say what turntable and cart you are using.

If per chance you have a DD turntable, and are using a moving iron cartridge, (such as a Grado), this is most likely your problem.  The moving iron cart picks up emi from the DD motor.
rdk777's avatar
rdk777
573 posts
 
Make sure your subwoofer is secured properly to the floor. I had serious resonance feedback/hum when I put the REL subwoofer on a Subdude Auralex platform.  It took me some time to figure out it was the platform -  then ended up blue tacking the subwoofer to my wood floor.  Got rid of the resonance and now it works fine. 

The problem may also be that your turntable is not isolated properly.  What kind of rack do you have it on?
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