On Wed, 31 Dec 2003 01:30:26 -0600, "Rusty Boudreaux"
wrote:

"Don Pearce" wrote in message
.. .
So from a purely theoretical perspective, how do these
different
cable structures lead to greater or lesser inductance in the
cable,
assuming a consistent overall gauge?

Thanks,
Colin

They don't. Braiding the cables closely together leads - as you
would
expect - to greater capacitance, not lower inductance. However,
the
net effect in network terms is that the overall reactance is
less
inductive. This is of course the same thing as more capacitive.

We might need to define braiding.

If the + wire is braided with itself and the - wire is braided
with itself but the two never exchange places then the inductance
probably doesn't change much (and probably not the capacitance
either).

However, if the + and - wires swap places ala twisted pair then
the inductance most certainly changes since the mutual inductance
terms partially cancel. Capacitance may or may not go up. In
the instance of a long twisted pair the inductance drops
dramatically over untwisted and the capacitance doesn't change
(the capacitance per unit length does increase slightly since
twisting the cable shortens it but not anywhere near the
magnitude of inductance decrease).

Of course, unless you have a pathologically deficient amplifier
none of this matters to audio.


I'm really not sure what you are saying here. Capacitance increases
because the cable is shortened? No.

Also, study the equation relating conductor area and separation and
you will find that the best way to increase capacitance between two
conductors is to bring the closer to each other. There is no question
of "may or may not go up".

With the question of twisted vs untwisted pair, neither inductance nor
capacitance changes. What does happen with a twisted pair is that
coupling to external fields cancels at each half twist, but that is
another matter entirely.

d

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