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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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lewm
13,027 posts
 

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?

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adamsrpm OP
12 posts
 

I dug-out the cheap cables that came with the turntable--including the power cable. Replaced the Pangea Audio phono cable and power cable. NO MORE HUM!!

I can't beleive it. Even at the highest gain setting--no hum. The phono cartridge is a Zu/DL-103 Mk.II. Everything sounds great, now.  Thank you to all who weighed-in on my problem.

carlsbad's avatar
carlsbad
1,551 posts
 

So now figure out the difference between the cables that work and the ones that don't.  Probably in the way they are grounded.  And then you can order upgraded cables that don't hum.

Audio envy has offered cables with versatile grounding systems and I think they are pretty good at customer support.   Other cable makers are too.

Congrats.

Jerry

hoosierinohio
162 posts
 

Sometimes a professional with a multi-meter and an oscilloscope is the best answer.  It's okay to admit, i have a son that's too busy doing this stuff because of people like me. 

Just because it has to be said, and I don't believe that anyone else threw this out there, it could be a Dinah-Moe-Humm.  If so, contact Frank Zappa.  I laugh deeply now, as a totally nerded Zappa fan. 

speedthrills
160 posts
 

Your cartridge is acting like a microphone and if its MC then its being amplified much more by your phono pre-amp than if it were a MM. Move your turntable further away from your system and the hum will reduce. Also, move your RCA cables from the TT away from any other cables including AC power cords. 

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