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Cable Asylum Interconnects, speaker wire, power cords. Ask the Cable Guys. |
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In Reply to: help with balanced cable posted by jamband guru on May 30, 2005 at 11:50:07:
See:
http://www.AudioAsylum.com/audio/cables/messages/103726.htmlWhat this advice boils down to ends up with the following:
a twisted pair using either 89259 or 1506A cores as the twisted pair (both wires the same for balanced, do not mix cores)
OR
Use a commercial twisted pair like 89207 or 89272A spaced shield consisting of a copper braid, this is connected to pin 1 at the source end only. If using a commercial cable like 89207, then use the shield provided.
A 16 ga. finely stranded copper wire (tinned OK) spiralled outside the shield, spiralled in the opposite direction as the twisted pair. This is connected to pin 1 at both ends. It is helpful for flexibility of this wire has a thin wall insualtion that is very flexible. Insulation dielectric quality does not realy matter on this wire, so some soft flexible PVC would be fine.
Then an overall jacket of HS or techflex, with HS being preferred
If you use thin wall polyolefin for the HS, it is not too ridiculously stiff.This geometry and construction should give better sonic results than retail/commercial XLR cable performance, as it isolates the ground from the signal wires a lot more, minimizing pickup of ground loop currents that can flow between chassis to chassis.
The ultimate expression of this geometry would be to use a second braid over the first one, after insulating the outer surface of the first braid. This second braid would replace the 16 ga. wire, and would then make the connection between pin 1 and pin 1. Then another layer of HS or whatever.
With two braids in play, the first layer of insulation might be better if it were teflon plumber's tape mummy wrapped, which should be more flexible than even thin wall polyolefin HS.
The end result with a two braid version is to have the twisted pair signal wires electrostatically shielded from the ground currents that might flow between pin 1 and pin 1, and due to the twisted pair being in the center (average) of the outer braid, then most of the magnetic field would not be picked up either.
With a typical balanced cable geometry, the pin 1 to pin 1 connection is made either via the shield braid, or via a third wire that is bundled with and right next to the twisted pair, often upsetting the twisted pair symmetry. Even though we have a balanced signal line, and the CMRR _should_ reject any such chassis to chassis ground current pickup that might be flowing in the pin 1 to pin 1 connection, in practice, if there is any RF present in that chassis to chasis flow, or it is wideband enough, it can overcome the CMRR of the balanced circuit, as most of the electronic types are only high in CMRR at low audio band frequencies. If it is a third wire that upsets the symmetry of the twisted pair, then even a situation with a high CMRR may not fully cancel out any pick-up from such a third wire.
Jon Risch
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- Risch Geometry Balanced Cable - Jon Risch 19:07:26 06/05/05 (0)
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