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Old 21st August 2012, 08:30 PM   #1
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Default Grounding question on turntable

Howdy yall, I seem to be having a strange situation that I can't figure out, maybe yall could help me out.
It concerns the grounding of a turntable to a preamp. My table is the stanton t.62 and the preamp is the art DjPre II, both of which have ground screws. With the ground wire connected between the two, there is a very loud hum, and it gets VERY loud when you touch the arm. Also, the volume of the hum changes by itself, one minute it will be incredibly loud, 15 minutes later it will be almost non existent.
The strange thing is, if I disconnect the the ground from the preamp, there is still a hum, but it's about half the volume, and it doesn't get louder if I touch the arm.
I can't really figure this, why is it so loud when it's grounded?
In both cases its terribly annoying, I would really appreciate if a more educated person than myself could shed some light on this subject.
Many thanks
-Cosmo

Last edited by cosmomurphy; 21st August 2012 at 08:33 PM. Reason: more info
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Old 21st August 2012, 08:40 PM   #2
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Location: Oakmont PA
My betting would be there is a bad shield wire on the RCA connection cable. It can also be in the cartridge headshell connections.

The other thing to be sure of is that both units are plugged into the same outlet. Also try unplugging one of the AC plugs turning it over and reinserting it.
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Old 21st August 2012, 09:15 PM   #3
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Thanks for the suggestions. both are plugged into the same outlet, I tried reversing the plug on the preamp(the table plug wouldnt reverse), but that didn't fix anything so I guess it might be the cartridge or the rca cable. I'll buy an extra cable and try it out, if anyone has any ideas in the meantime they would be greatly appreciated.
Thanks
-Cosmo
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Old 22nd August 2012, 06:21 AM   #4
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You were right about the headshell, when I twist it ever so slightly the hum goes from loud to quiet and vise versa, and if I get it just right it keeps the hum down.
That being said, I would rather not have to fiddle with the headshell every time I play a record, so that raises another question.
Do you think that the problem lies in the headshell, the cartridge, or the connection inside the arm?
I ask because I'm not quite sure of the mechanics of the cartridge and arm, but it would undoubtably be easier to replace the cartridge and or headshell.
Thanks-
Cosmo
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Old 22nd August 2012, 11:15 AM   #5
andyr is offline andyr  Australia
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Location: Melbourne (Oz, not Florida!)
OK ... it has to be said ... possibly you need to change your TT? Maybe it's just inadequate?

I say that because I have never experienced any hum with my LP12 ... using 2 different arms, several different cartridges, several different phono cables and several different preamps/phono stages.

Regards,

Andy
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Old 22nd August 2012, 04:22 PM   #6
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Sure that would be a great solution. If I had the money to drop on a sondek, or at least a t1200, I would in an instant, but thats almost two months pay for the lp12(used), so I'm forced to look for a more frugal solution.
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Old 22nd August 2012, 07:44 PM   #7
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Just clean the headshell contacts and be sure they are springing properly. The hum may actually be from the mechanical connection holding the headshell in.

It is rare for the wires inside the arm to fail. Headshells used to be $7! Haven't bought one in a long while!
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Old 23rd August 2012, 12:59 AM   #8
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Thanks simon, will do.
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Old 10th November 2012, 12:50 PM   #9
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Try using an "ink eraser" on both the headshell contacts & the tonearm contacts. "Ink eraser" because they have an abrasive grit in them, that will clean any corrosion off the contacts. You can buy a pencil style combo pencil/pen eraser in any office supply store. The pencil style should be small enough to fit into the headshell connector on the tone arm.

It should go w/o saying, but always blow the eraser rubbings & grit out of/off whatever you clean.

MLStrand56
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