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Turntable hum ground issue?

Help? Just switched amps from a Mcintosh MA-6500 to a MA-7000 and I am getting a pretty bad hum from my VPI Prime. I have swapped cables. same issue, when i lightly touch the tonearm wire (between tonearm and rear connectors) the hum increases BUT when I touch the ground connector on the back of the VPI the hum reduces considerably. Any ideas? The hum even reduces if I touch the top of the amp. Sounds like a ground issue but not sure what to do to trouble shoot. Also it was happening with my other amp but not as bad. Also touching the cartridge does not affect it one way or the other 



marsrecords
4 responses Add your response
atmasphere's avatar
atmasphere
11,794 posts
 
Sounds like something in the arm wiring is messed up. Grounding the ground wire is the clue- it increases hum. Sounds like the arm tube isn't grounded properly.
marsrecords OP
24 posts
 
Tried bringing the amp to another circuit and though it may have reduced it a little it is still there 
jayctoy's avatar
jayctoy
4,040 posts
 
Marsh you need ground wire from your turntable to your phono preamp or preamp.
mattmiller's avatar
mattmiller
1,497 posts
 
Using Unbalanced cables causes this ground loop hum, try plugging amp directly to wall outlet by it self, everything else plugged into a standard power strip into a different outlet. Also, make sure ALL connections from cartridge clips (examine if any insulation on cartridge leads are missing or torn...the wires are very thin and need to be completely covered to clip) on back are not loose! Make sure there are no lamps/lights that use sliders or dials on the same circuit that will cause buzzing too. Also, keep IC's and spkr cables away from power cables (best u can).


Matt M
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