john stewart wrote:

kyser wrote:

"Chuck Harris" wrote in message
...
Patrick Turner wrote:

kyser wrote:

I'm embroiled in a discussion on aus.hifi with a poster who recommends
the
use of RG58C/U as speaker cable (with alleged sonic improvements over
standard figure-8 type flex).

Wouldn't the combined inductance/capacitance of this stuff constitute an
LC
filter causing signal attenuation or, worse, amp output stage
instability
over anything but a short run?

Patrick Turner? Anyone?

TIA


The typical inductance of a 3 metre speaker cable is perhaps 2 uH,
and the roll off is well above 20 kHz, as the pole formed by the
LR filter is at 637 kHz..
The capacitance between the pair of cables used may only be
200 pF, causing a pole at some RF frequency.
the L&C components would form an LC filter, which would display
resonances
at some RF, but generally, the L and C components of speaker cables
are utterly negligible and have SFA effect on the engineering
measurements.


Hi Patrick,

I have heard one explanation for sound improvements from odd speaker cable
remedies that I find plausable. Some of the "boutique" amplifiers are so
incredibly unstable at frequencies above the audio spectrum that the RF
characteristics of the cable can start, or stop the amp from oscillating.
Amps that are oscillating always sound awful!

-Chuck, WA3UQV

This was one of the arguments I advanced at aus.hifi for NOT using coax,
given that the people who do so are just as likely to use some form of
"exotic" amp of unknown stability.

A length of coax sourced & terminated in other than it's characteristic
impedance will support standing waves. Wavelenght depends on the cables
electrical length. You are absolutely correct IMO with your argument.
It's possible that a length of that cable could drive an SS Amp which
usually has large BW into instablity. Would be an interesting experiment.

Anyone got one they would like to sacrifice? John Stewart

I have never noticed instablities in normal bandwidth amps when working properly.
I know a guy whose SS amps go to 1 mHz, -3db, and lord knows what instability he
has.
Tube amps usually cut off at about 70 kHz, but still need to be arranged to NOT
oscillate, when C loads are used, especially if the OPT has high leakage
inductance.
L&C in cable/speaker combinations shouldn't affect the amp.
If an amp can be made to oscillate, under any circumstances whatsoever,
someone ain't done his home work.
Unconditional stablity is where we should aim.

Patrick Turner.