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Hum with Ypsilon MC26L SUT that goes away with touching

I need help solving the hum problem.

Ikeda Kai cartridge -> Ypsilon MC26L SUT -> Ypsilon VPS 100 -> Cary SLP 05 -> Cary CAD 211FE monoblocks -> KEF Blade.
ICs between MC26L and VPS100 Stage 3 concepts RCA
ICs between VPS100 and  Cary SLP 05 Stage 3 concepts XLR
Cary SLP 05 and Cary monoblocks Shunyata RCA
Cary monoblocks to KEF Blade Shunyata speaker cables.

Connected ground from tonearm phonocable to SUT grounding post ->I hear 60 hz hum
Connected ground from tonearm phonocable to SUT grounding post + connected  SUT grounding post to VPS 100 ground ->I hear 60 hz hum (slightly decreased)
Connected ground from tonearm phonocable directly to VPS 100 ground (I read in the forums to try this) ->  I hear 60 hz hum
If I touch the body of SUT (metal) with one hand and touch the metal frame of the rack that sits directly on the floor, the hum disappears in all the above situations.

I used two shorting RCA plugs into input loading of SUT with tonearm cable connected to input-> No Hum 
I used two shorting RCA plugs into input of SUT without tonearm cable-> No Hum
I used two shorting RCA plugs into output loading of SUT -> No Hum

Any help in solving this hum problem is greatly appreciated.

Thanks
Kanchi
kanchi647

Showing 4 responses by lewm

lewm
12,445 posts
 

Seems the problem was solved by the OP in August, 2020.

lewm
12,445 posts
 
Signal ground is essential. Shield is optional. If there is no connection between one unit and the other via ground for the audio signal to travel, then you would only have one single piece of wire. In my mind, that would not work at all, but is that what you Are saying you have?
lewm
12,445 posts
 
Also, many audiophile single-ended, RCA-terminated ICs are built such that the shield is only grounded to one end.  The manufacturer will typically mark the cable for polarity. In such cases, it could make a difference which end is connected to the input vs the output side, in terms of hum and noise.  I take it that BOTH the Ypsilon IC and your home-made IC cured the hum problem.  Did you connect the ground conductor and the shield to BOTH ends of the home-made cable or just one?
lewm
12,445 posts
 
If hum does not go away when everything is grounded to everything,  start removing ground wires, one by one.  But it does seem your SUT wants to be grounded to something, and you are already grounding the tonearm to the SUT and the SUT to the phono stage, correct?  Finally, you have several pieces of gear in your phono chain.  Are all the items plugged into the same AC source (same wall socket)?  If not, they should be. Small AC voltage differences in grounding of one wall socket vs another, even in the same room off the same circuit breaker, can cause hum.
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