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Turntable Hum

I've got an old Technics that is giving me fits...there's a slight hum present, that's there regardless of whethter the unit has a headshell attached or not, and regardless of whether it's AC power is plugged in. When I swing the arm across the platter, the hum varies from crackling and loud to nothing. It's not near a transformer or anything like that. Any ideas? I'm really perplexed by the behavior of the arm.
vanmeter
vanmeter OP
33 posts
 
They come out of the turntable, which is mounted on the wall, through an opening in the back of the shelf, and connect directly into the preamp, which sits on a shelf underneath, crossing nothing. They haven't been moved in a year or more, but it could've been that I didn't notice the problem when I moved into my current location. But they're not original; they were replace by the former owner with something sturdier and heavier gauge, so maybe the connections are going.

I've may try wrapping the cables in foil temporarily to see if that kills the problem...at least that could narrow it down.

Thanks!
rwwear
2,847 posts
 
It sounds like the ground wire may have lost it's connection inside the arm or where it attaches to headshell or output cables. Do you get strong left and right output from the TT?
jimbo3
304 posts
 
I had a situation where the clip was hanging by only aone or two strands of the arm wire. It happened to be a ground wire and there was a terrific hum. After re-soldering the clip to the wire, the hum disappeared.

Check all the tonearm wire connections!!

Jim
vanmeter OP
33 posts
 
I'll let you all know as soon as I have time to check everything...so far it's not a loose clip or anything, and I'll report back when I've had the chance to devote myself more fully...
vanmeter OP
33 posts
 
I've done a little searching around and discovered comments here and there regarding the change in capacitance that can occur with heavier RCA cables, which is what the prior owner of my deck put on...I'm not certain what the brand is and I'm not near the deck right now to look, but they're very thick cables with shielded plugs, and the cable itself is probably 75% longer than a standard table cable would be.

I'm starting to wonder if this could be where my problem is coming from, since otherwise it would appear to be in the tonearm wire. I haven't checked the solder connections for the RCAs yet, but I'm wondering if I should just replace the fancy cables with plain old RCAs when I do to see if it makes any difference.

Is there a hard and fast rule about what cables are usable with turntables?
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