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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 2 responses by dover

dover
2,279 posts
 
@kanchi647
Unfortunately like many expensive audio cables, the Stage 3 Concepts phono cables are rich on fancy materials, multiple shields, and fancy sounding jargon. The reality is that there are no electrical specifications on their website for their phono cables.
Given that they claim 4 layer shielding for their phono cables, and use star quad ribbon configuration for signal  it could well be that it is the inherent electrical parameters ( LCR ) of the interconnect that are inducing hum between the transformer and phono.  For example, cables that are capacitive can be prone to hum/rf, particularly in this situation where the signal coming out of the transformer is high voltage, very very low current, meaning the signal is more sensitive to the cable.


dover
2,279 posts
 
@kanchi647
Yes, but star quad will have much higher capacitance than a single twisted pair. Plus they use a ribbon wire - it would be interesting to measure the capacitance - I suspect it is not as low as you might think.

Otherwise it could be the shield - you could try connecting the shield at one end only to true ground - not the earth posts on the phono/SUT.

When you are touching the SUT you are grounding it.
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