SUT Interconnects

Could you please explain why it is important to have low capacitance cable before the transformer. how does that affect the transformer ?

The inductance of the cartridge and transformer in parallel with the capacitance of the tonearm cable causes an electrical resonance. Best to keep that resonance as high as possible. Depending on the transformer design you may well have to load the transformer in a certain way to deal with this resonance. So its best to minimize variables by minimizing the capacitive aspects since there is little you can do about the inductances involved.

This is one reason why I prefer to run direct if I can.

@atmasphere 

Very interesting! Your vast and deep expertise is always appreciated. 

Considering that SUT box users like me are, for practical reasons, usually limited to a 0.5m minimum cable length on either side (and usually RCA) - what are some good "audiophile" cables with the smallest possible capacitance per foot? Capacitance specs aren't always listed. From the specs I have seen, Cardas interconnects seem to consistently show an impressively low capacitance - much lower even than my AudioQuest phono / LP cables (AQ's normal interconnects are WAY too high). Is there anything likely to be better than Cardas for this role?

I know that besides a spec, there are some clues you can use - like avoid large gauge wires (keep it smaller than 23 AWG) and avoid braided geometries. The Stax headphone cables uses a ribbon layout (with large spacing gaps) to minimize capacitance. 

20pf/foot is a practical value for a cable. Mogami makes a console cable that specs in this area. Since transformers can receive either a single-ended signal or balanced, you could run a balanced connection from your arm to the SUT and thus obviate the sonic attributes (or artifacts, however you want to look at it) of the cable.

Shielding adds capacitance. Cable geometry also affects capacitance. The 12AX7 tube, often used as the input voltage amplifier in tube MM stages has a high Miller capacitance that adds to cable capacitance. Transistors also add capacitance at the input.

I use a very short 0.4m Van Damme XKE cable terminated with ETI connectors, made by Aurealis Audio, between my EAR MC4 SUT and Nagra VPS phono stage: www.aurealisaudio.com.au/phono-cables/

This is very low capacitance at less than 50pf per metre, is inexpensive and sounds very good. It is also the same as the captive cable of my Audio Origami PU7 arm.