My Impossible hum issue.


I have done everything that I have read about ground loops without success. My system is on an outlet that goes directly to the main panel with nothing else plugged into this circuit. None of the usual suspects are in this room like TV, radio, appliances or flourecent lighting. When using any other source other than the turntable, the system is dead silent. The turntable is on a wall mount turntable shelf. The speakers are on stands. This hum is only present when the turntable is the source. The hum is much louder with a MC cartridge than a MM cartridge. The hum is present when connected to an external phono preamp or the internal phono preamp of the my system preamp. I have tried every combitnation of grounding and not grounding. Whether or not I plug into the wall outlet or power conditioner/surge protector the hum persists. I beleive that I have tried everything except a different turntable. I have made sure power cables, speaker cables and interconnects don't cross each other. I've tried everything except moving to another state or hiring an exorcist.

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Showing 6 responses by lewm

etbaby, I don't think an isolation transformer would solve the OP's actual problem, since the short in the ground connection occurs AFTER where the ISO Max transformer would be inserted, between the AC source and the power cords. He had an interruption in audio ground.

Am I missing something? We do know the cause of this problem, and it’s been cured. Yes? A defective IC. 

More to the point, you might contact Pangea or your vendor and ask for a return authorization, on the basis that their ICs seem to have an internal short circuit on the ground side. By "internal" I mean that the issue probably is inside the insulating sheath or outer cover OR it's at one end where the wire is soldered to the ground side of an RCA plug. (It's unlikely to have been a problem with an AC cord; in that case you would have no power to the TT.)

Also, you haven’t ruled out an internal break in an IC wire, most likely the phono cable but could be elsewhere, that interrupts grounding. To check that just insert some cheap alternative ICs in place of what you’re now using. For one, try the Sony supplied phono

cable. Like Russ suggested also check cartridge pins, internal tonearm wires, and joint between headshell and arm wand. Is it tight?

Russ’s guess is as good as mine. You’ve eliminated most other options.

Could there be a broken ground connection inside the jacket of one of your ICs?