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Old 27th August 2011, 04:44 PM   #21
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Originally Posted by AndrewT View Post
...Ground current could be directed along the screen if needed or it can be single end connected as screen only. The amplifier sees the voltage difference at the receive end of the Flow and Return pair. I don't think that can be said for a Coax, which must have the screen connected at both ends.
I think DF96 has a point. Shield (screen) does get connected to return path at receiving end in both cases, either twisted or coaxial. In twisted pair case, if the shield is only connected to return conductor at transmitting end, it still indirectly gets connected via return path at receiving end.

I suspect this practice of connecting shield only at one end came from ground loop problems that themselves came from confusion of signal ground (return) and chassis ground.
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Old 27th August 2011, 05:38 PM   #22
infinia is offline infinia  United States
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I suspect this practice of connecting shield only at one end came from ground loop problems that themselves came from confusion of signal ground (return) and chassis ground.
yes indeed , that is a big problem with single ended connections between boxes on different AC circuits, SMPS, class D, and/or digital noise. There is no common mode rejection, so any electrical potential difference in "grounds" can be impinged on a low level signal. ( ie hum or low signal to noise ratio S/N,). In audio and instrumentation, the Pro's go with differential signals, In audio choice goes to XLR plugs and jacks.
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Old 29th October 2013, 07:28 PM   #23
RCruz is online now RCruz  Switzerland
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I need a new interconnect for my TT.
The best I have used so far was VDH coax but now, short of money, I am planning to build a new set of cables.

After readind about the pros and cons of coax and twisted pair, I am wondering if it is a good idea to twist two coax cables, use the inner wires for signal and return and connect both shields only on the input side.

This way, both signal and return wires will have it's shield and they will be twisted.

Please let me know your opinions.
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Old 29th October 2013, 09:20 PM   #24
DF96 is offline DF96  England
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You will lose most of the benefit of twisting, as the two inners will be spaced apart. About the only benefit of your idea is that the capacitance will be half that of a single coax - but that is not normally an issue with a TT interconnect, as sometimes extra capacitance is needed.

Twisted pair within a single shield may be better.
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Old 30th October 2013, 07:39 PM   #25
RCruz is online now RCruz  Switzerland
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Well, I am using singularly thin coax so the inners will be suitably spaced apart.

But you did not tell me that I would experience some kind of downfall, so I believe I will loose nothing by doing it this way.
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Old 30th October 2013, 10:17 PM   #26
DF96 is offline DF96  England
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You might not get much interference rejection; that is what you will lose. Simple coax would be better. Shielded twisted pair better still.

Your idea would work in a situation where low capacitance was the aim, and interference was not an issue. Pickup catridges are not this situation, so you are solving the wrong problem.
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Old 31st October 2013, 10:18 PM   #27
RCruz is online now RCruz  Switzerland
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Well, what I need is a cable that does not pick up interference.

The VDH I use, can be left connected only to the riaa amp (not connected to the cart) and there is no hum pick up.... other cables just act like antenas and the hum only goes away when I connect the cart closing the loop.
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Old 31st October 2013, 10:31 PM   #28
AVWERK is offline AVWERK  United States
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I have made some Audioquest type DBS style 36 and 72 volt interconnects with and without single ended shields, and overall the shielded single ended for phono was the quietest way on my system.
Not much noticable noise or hum either way between pre and power connections with the same cables.

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Old 1st November 2013, 09:55 AM   #29
DF96 is offline DF96  England
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Quote:
Originally Posted by RCruz
The VDH I use, can be left connected only to the riaa amp (not connected to the cart) and there is no hum pick up.... other cables just act like antenas and the hum only goes away when I connect the cart closing the loop.
If connecting a cartridge to a cable reduces hum picked up by the cable then your problem is capacitive coupling of hum probably caused by inadequate or missing shielding/screening. Nothing to do with antennas - hum and RF are different problems.
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Old 4th November 2013, 05:10 PM   #30
RCruz is online now RCruz  Switzerland
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So what I need is to try to eliminate capacitive coupling of hum using shielded cable..... my build does it very well, already tried it with good results between the TT cart and the riaa amp..... now about it's subjective sound is another story.... it just does not present highs the way the VDH cables do.
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