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Discussion Starter #1
It's really disappointing not to be able to use my task light for its intended purpose. Mounted on the side of my turntable's dust cover, my wall-wart powered LittleLite induces a low-level hum into the cartridge circuit even when the lamp is turned off! Stranger still: the hum only starts when the stylus is lowered onto a spinning record! I'd understand that last bit if the vinyl record had metal impurities, because moving metal near cartridge windings could possibly induce a current of its own (the definition of an MM cartridge!). But the hum is there even on virgin-vinyl pressings.

Only when the wall wart is unplugged does the hum vanish. I haven't yet tried to plug the wall wart into a different circuit branch because an extension cord is unwieldy, not to mention un-pretty. And I refuse to run a dedicated line for just the lamp! :foottap:

Oh yeah, almost forgot - all gear, including the 'table and it's dedicated speed controller are plugged into an AC regenerator (PS Audio Power Plant Premier).
 

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A few diagnosis ideas. Try plugging the wall wart into a short extension cord and moving the wart farther and farther away from the cartridge, see if the hum level goes down as it moves away.

Also, if you are willing, lower the cartridge onto a turntable with no LP on it that is not spinning, very gently. With the light turned on, is there hum?

What if you lower the stylus off the edge of the record?
 

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Discussion Starter #3
Always happy to follow your lead! Before getting into that methodology, though, I rerouted the RCA phono cable as a first strike. Hum is now reduced, but still audible through headphones. I'll report back next chance I get. Along with your advice in this thread, I thought I might also try my hand at pursuing the benefits of a low noise floor. First things first. See you soon!
 

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Always happy to follow your lead! Before getting into that methodology, though, I rerouted the RCA phono cable as a first strike. Hum is now reduced, but still audible through headphones. I'll report back next chance I get. Along with your advice in this thread, I thought I might also try my hand at pursuing the benefits of a low noise floor. First things first. See you soon!
Good move. ALWAYS try the simple, easy, cheap fix first, even it it seems like a silly idea.
 

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Discussion Starter #5
Okay Wayne, not to disappoint you but the strangest thing happened on the way to the forum. The record I first noticed the hum on wasn't due to the 'table at all! It was hum from the guitar amps in the recording! There is still residual hum in the rig, though, so I'll follow through with some of your tips and report back soon.


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