unshielded twisted pair/tri for turntable to phono pre interconnects

[dougi]

I'm about to go back to a MM cart. The lowest capacitance interconnects I have are some short Kimber PBJs which are unshielded tri-braid. I have used them for 10 years and never suffered any apparent issues due to induced interference. My alternative is some Project connect-it Es which has capacitance probably too high for MM (130pF for the length). That cable is a twisted pair, with shield, shield connected to -ve only at the pre-amp intended end.

You see all sorts of comments saying you must use shielded cable between the turntable and the phono pre. Why? Doesn't twisted pair (or tri) mean interference is largely common mode which will be largely rejected by the differential op amp or whatever in the phono pre input? Chassis grounds are always handled by the separate turntable to phono pre ground wire to deal with the separate ground loop issues.

Is a shield at all beneficial if using twisted pair/tri interconnects? It will be connected to the same -ve pins in the phono pre-amp and hence any interference on the shield will still be present on the -ve won't it? That -ve shouldn't be connected to the chassis ground as that would create a ground loop.

I am missing something?

 

[somebodyelse]

If you don't have an interference problem then use your Kimber and be happy - its interference rejection is good enough in your situation. The twisted pairs, starquad, and various shield options are all things that can contribute to reducing interference, as is physical separation, and you just need to apply enough of the right one(s) to deal with the interference present in your environment. There's some explanation of how they work here in section 3.6 - About Cables and Shield Connections. Other sections deal with grounding in great detail. See also Benchmark's starquad vs. twisted pair demo for when 'largely' isn't enough.

Depending on your cartridge, the internal arm cable and your phono input 130pF may or may not be ok - check the specified load for the cartridge and add up the capacitances.

 

[dougi]

If you don't have an interference problem then use your Kimber and be happy - its interference rejection is good enough in your situation. The twisted pairs, starquad, and various shield options are all things that can contribute to reducing interference, as is physical separation, and you just need to apply enough of the right one(s) to deal with the interference present in your environment. There's some explanation of how they work here in section 3.6 - About Cables and Shield Connections. Other sections deal with grounding in great detail. See also Benchmark's starquad vs. twisted pair demo for when 'largely' isn't enough.

Depending on your cartridge, the internal arm cable and your phono input 130pF may or may not be ok - check the specified load for the cartridge and add up the capacitances.

Thankyou! That Jensen reference is good. The Project cable's capacitance alone is 130pF. With the Kimber I can get to around 100pF total which is the recommendation for the cart.