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What is the "usual" source of hum between a turntable and phonp-preamp??

I just purchased a U-Turn Basic TT with an acrylic platter and cork mat with an Ortofon 2M Red cartridge. The table is plugged into a Moon Audio LP-110 phono pre-amp. Moon Audio does recommend to isolate the box away from the turntable. I have currently placed it on a 21inch formica platform stand.  The hum is most audible in the lead out groove, and between tracks.  The sound is very good, BUT I can still hear an undertone of hum when the volume is half way, that is between  55-60 steps on a volume control calibrated from 1-99.  The pre-amp is a Conrad Johnson PV-14SE which the Moon phono box is plugged into

I aware that the hum problem can be caused by the phono cable of the turntable ( which is somewhat cheap) or the connect IC which  is one of the Canare cables which cost $40.00 to $50.00. It appears well made. The   U-Turn TT rep informed me that the left channel input on the table functions as a built in ground.  The Moon box has a separate grounding screw which I am not using.   Thank you,   S.J

  

sunnyjim
dill
2,531 posts
 
You need to run a ground wire from the ground of the turntable to the Moon Box grounding screw.
jmcgrogan2's avatar
jmcgrogan2
6,346 posts
 
+1 what dill says. Generally a hum from turntable is a grounding issue.
sunnyjim OP
927 posts
 

To Dill and jmcgrogan2,    U-turn indicates that the turntable uses has a ground built in the left channel RCA input. There is NO ground screw ON THE BACK OF THE TABLE WHERE THE RCA CABLES ARE PLUGGED IN. 

Let me know if you have any other suggestions. I tried to contact Moon Audio, but got no response so far  I will also contact  U-Turn  customer service about the problem.    Thanks,  SJ 

 

dill
2,531 posts
 
I understand what U-Turn is saying. It is a budget turntable and they don't provide a separate ground. Try wrapping a wire around the outside of the metal part of the RCA plug of the left channel output, get it as tight as you can, then attach the other end to the ground screw of the Moon. If that doesn't work try the reverse. Wrap the wire around the RCA plug left input of the Moon and run a short wire to the Moon ground. 
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