On Mon, 10 Nov 2003 09:02:23 -0500, "Robert Morein"
wrote:


This suggests that there may be a phenomena in the cable that produces
audible distortion. Three candidates are known:

1. Skin effect
2. Dielectric memory
3. Microphonics

Don'r worry about dielectric properties for speaker cables.

Take a speaker of R=10 Ohms, an amplifier giving V=10 Volts (RMS)
you get I=1 amp and Power = 10 Watts.

Now take the same 10 Volts out of the amp at 20,000Hz (worst case) and
see what current is needed to charge and discharge the capacitance of
the cable.
Say the capacitance is 50pF/metre and we have 20 metres (LoT's) of
cable =1000pF
Call 2*PI = 5.
The reactance of the capacitor is X=1/(2 pi f C j)= 1/(5*2e4*1e-9) =
1/1e5*1e-9) = 1/(1e-4 )
The current charging this capacitance is I = V/X = 10 * 1e-4 = 1e-3 =
1 milliamp. This is all you have to play with.

You are going to have to be very creative to distort this 1 milliamp
in some way, enough for it to create a distorted voltage across the
output impedance of the amp,sufficient to be audible against your 10
Watts signal, even if you used the worst dielectric on Earth.

Say you manage to distort this 1 milliamp by 10% (very generous
indeed) and the output impedance of the amplifier is 0.1 Ohm
(generous) The amplitude of the distortion is then 10 microvolts and
the distortion power at the speaker W=V^2/R =10e-9 Watts. A
signal/Distortion of 1000,000,000

Yep, the idea is total ********.