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Turntable hum from RCA cables.

 

New member
Username: Tsuellentrop

Post Number: 1
Registered: Jul-10
Searched everywhere but couldn't find an answer that worked for my exact issue.

First, the gear:

Pro-Ject Debut III TT - Stock
Pro-Ject Phono Box II
Pioneer Elite - VSX-21TXH Receiver
Audioquest Sidewinder interconnects from the Pre-Amp to the receiver.

The Problem - Hum:

There is a hum in the system which seems to be caused by the RCA cables, mostly the right channel, to the pre-amp. When I touch it, the hum increases. I have found what seems to help, but not eliminate the hum, is to raise the pre-amp straight above the TT as far as the cables allow. It seems to be only vertically, not if I stretch it side to side, maybe because side to side makes the cables touch each other and the ground more.

I have the ground from the TT to the pre-amp, and have tried my Panamax power conditioner with no change. Both the TT and pre-amp are plugged into the same outlet. I've wrapped the cable in aluminum foil but hear little if any difference but I plan to try again with multiple layers on both cables. Also tried flipping the power blocks for both the TT and pre-amp in each socket up-side-down, no change. Also, I have tried best to keep the interconnects from crossing any of the power cables, have when moved close to them I noticed they do make the hum louder.

I think I've covered everything, any ideas? I'd love to just swap the RCA cables but they are hard-wired to the turntable.

Thanks,
Tim
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 15029
Registered: May-04
.

Most likely the problem is in the receiver sine this is not a known problem with the table or pre amp. If there's no phono section in the receiver, a mass market manufacturer is unlikely to spend large amounts on shielding the power transformer. The interaction between what appears - from what you've posted - to be the transformers in the receiver and pre amp looks like the problem area. Wrapping the cables in more foil isn't likely to help since it is the amount of coverage by area that counts here. Even the slightest area open to RFI/EMI will allow for hum. And, anyway, induced hum of ths sort typically doesn't come from well shielded cables. Changing the table leads also isn't likely to solve your problem since bad leads on this table are not a known issue. You're far better off with captive leads anyway.

First thing to try would be reversing the direction of the cable between the pre amp and receiver. If the cables have their shield lifted at one end, you neeed to properly orient the cables to minimize hum. Next, try lifting the AC ground to any three pin AC cables in the table/pre amp/receiver. Use a $0.99 ground lift adapter you can pick up at any hardware store or even the grocery store and eliminate the ground pin to any of these components.

Next, move the pre amp away from the receiver. You've not said whether the hum appears with the table disconnected from the pre amp. If it does, then just move the pre amp as far away from the receiver as any cable you have allows. Cable quality is not as important as cable length for this, if you have a 6' cable that came with a satellite dish, use it for experimentation. If the hum diminishes the father away the pre amp sits, then you have your answer. Do not extend the leads from the table but you can place the pre amp as far away as your cable will allow since it is now sending a line level signal out to the receiver. Finally, try running a ground line between phono pre amp and the receiver.

There are quite a few things you have yet to try with this issue. Do those things first and report back.


.
 

Platinum Member
Username: Nuck

Post Number: 15232
Registered: Dec-04
The hum thing is usually solvable, but not without some effort, Tim, and not much money.
Jan gave you the first basics to try, how did you do?
 

New member
Username: Tsuellentrop

Post Number: 2
Registered: Jul-10
So it's been a while but this is what I have tried or forgot to mention:

Hum only exists when the TT is plugged into the pre-amp but it exists when the TT is on and off, including unplugged from the outlet.

Swapped directions of the RCA cables from the preamp to receiver and tried different calbes, no change.

Switch the R/W from TT at preamp and the hum follows the red rca. If I unplug the red and touch it to the ground on the preamp there is no hum, so would it be a good idea to somehow connect the red rca to the ground when it is plugged in?

The biggest effect on the level of hum is handling it. Extremely loud if I wrap my whole hand around it.
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