[GreenKeys] quality fabric covered cable

[Gerry Block]

Craig,

  Very good.

  For any normal individual, there are only two things worth doing.  Gold is
good for analog low level cables, as oxidation is always there a really bad
thing.  And low resistance (read: larger) is good for speaker cables.  This
wasn't a big thing in the tube amplifier days because the amplifiers have
matched output impedance but most speaker crossovers are designed these days
expecting a zero source impedance.  My DC300A amplifiers have an output
impedance at the lower frequencies of something like .001 ohm.  Years ago I
was involved in some experiments with this (easy experiment: put a very
large rheostat in series with the speaker leads and run your test) and this
will make more difference in sound quality than almost anything you can do
in an audio system.  You can make a solid state amp sound like a tube amp
pretty quickly.  We did this listening to live sound sources through some
good microphones.

Gerry
AD6MC

-----Original Message-----
From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Craig Sawyers
Sent: Saturday, May 02, 2009 2:06 AM
To: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] quality fabric covered cable

Yeah - that does sound rather daft.  Digital transmission depends on a
number of characteristics, key among which in audio use is suppressing
timing jitter.  There have been double blind experiments at the University
of Essex in the UK by Prof Malcolm Hawkesford that demonstrate that the
threshold of audibility for digital jitter is 20ps (I kid you not).

This demands a cable which has a constant characteristic impedance down the
cable (to suppress local reflections) and the correct termination to prevent
termination reflections.  Of course you also need sufficient bandwidth so
that the rise time of the signal is not degraded - increased rise time
implies increased cable induced jitter.  But a halfway decent coax has a
bandwidth of a few GHz, and in general the runs are short in any case in
domestic audio.

I've been doing some real-world tests on audio cables, mainly loudspeaker
and power cables.  What is clear is that there is a strong correlation
between measured performance (using either time domain reflectometry or
network analyser) and audible result.  There is also a measurable effect
(and the method is critical in order to eliminate artefacts) in cable
direction, both to DC and AC signals.  Usually this is transient, settling
down in an hour or two, but only when a signal is applied.  All this comes
with a proviso - I have measured no difference between high quality copper
and silver in the same cable construction.

Silver plated copper seems to be a bad thing - in space use, there is an
effect called "red plague", made worse by elevated temperatures and an
oxygen atmosphere, in which copper migrates through micropores in the
silver.  Also, there is evidence that silver plating copper makes skin
effect worse - someting to do with making surface roughness worse.  In
microwave waveguides, the copper is brought to a high polish before silver
plating to prevent this happening.

Craig


> -----Original Message-----
> From: greenkeys-bounces at mailman.qth.net
> [mailto:greenkeys-bounces at mailman.qth.net]On Behalf Of Bryan Brodie
> Sent: 02 May 2009 05:30
> To: greenkeys at mailman.qth.net
> Subject: [GreenKeys] quality fabric covered cable
>
>
> I know that you thrifty old salts and budget minded hobbysts will
> appreciate this value of THIS quality cable
>
> http://www.usa.denon.com/ProductDetails/3429.asp
>
> Also available at a non-discount from amazon.com - be sure to read the
> customer reviews!  ;-)
>
> http://www.amazon.com/Denon-AKDL1-Dedicated-Link-Cable/dp/B000
> I1X6PM/ref=sr_1_1?ie=UTF8&s=electronics&qid=1241238525&sr=8-1
>
> note: this is a REAL product...
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