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From: dms@fluke.UUCP
Newsgroups: net.audio,net.analog
Subject: Re: need interconnect cable recommendations...
Message-ID: <1738@vax3.fluke.UUCP>
Date: Mon, 14-Jul-86 14:30:33 EDT
Article-I.D.: vax3.1738
Posted: Mon Jul 14 14:30:33 1986
Date-Received: Wed, 16-Jul-86 07:57:13 EDT
References: <2107@orca.UUCP>
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Organization: John Fluke Mfg. Co., Inc., Everett, WA
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Xref: utcs junk:1366 net.analog:949

The thing that matters a whole lot more than so-called "oxygen-free"
copper when it comes to shielded audio cables is the coverage factor
of the shielding.  The main problem with cheap shielded cable is that
the braid is pretty sparse and may only cover half of the area.  The
more dense the braid is, the better it keeps out interference.  The
frequency of the interference is also important, but with audio cables
you're usually trying to keep out everything from power line frequency
to hundreds of megahertz, so you need dense coverage.  No braid can give
complete 100% coverage.  Foil-covered wire gives the best shielding, but
is not as flexible.  If low capacitance is critical to you, scope probe
wire would be excellent (probably overkill on all regards, but I notice
the request for info came from Tektronix).  
	I don't know how oxygen-free "oxygen-free" interconnect cables
are but I'd be curious to know the oxygen content in ppm for standard
anealed copper versus that of the fancy stuff.  It's true that grungy
connections have been known to form copper-oxide rectifiers unintentionally 
and rectify large rf signals (e.g. you live under an a.m.  transmitting 
tower) giving you continous radio music no matter what you're listening 
to.  If you're afraid of copper-oxide discontinuities in your wire you 
could use silver wire (silver-plated wire is readily available for r.f.
work) which is lower resistance than copper, with the added benefit that 
silver does not oxidize as easily as copper, but when it does, its oxide 
is electrically conductive.  
	Regarding the alleged high oxygen content of normal wire:  When
copper ore (sulfides and carbonates generally) is refined, the first
step is "roasting" which is heating the ore in an oxidizing atmosphere
(air) this burns the sulfer out of the sulfides, converting them copper
oxide, and creating the sulfer dioxide emissions smelters are famous
for.  This step also burns out most arsenic, selenium, tellurium and
some of the lead which are generally present in copper ores.  Then 
the oxidized ore is heated with flux in a reducing atmosphere
where the oxygen combines with carbon in the fuel leaving metalic
copper, and the nonmetalic residue dissolves in the flux becoming the
slag.  This step is the reason why smelters and refineries, especially
in the old days, frequently have the words "reduction company" in their
name.  An ancient but still used part of the last operation is to insert
a large wooden pole (tree-trunk) into the melt towards the end of the
operation.  Much of the remaining oxygen combines rather spectacularly
with the carbon of the log, purifying the copper a little more.  Then
the molten copper is poured into molds, and as it cools, oxygen comes
out of solution since solid copper cannot hold as much oxygen as liquid
copper.  The oxygen erupts from the surface giving these raw ingots the
name "blister copper".  If you made you're wire from this (which 100
years ago you probably would have) you might have problems.   All
copper used for electrical conductors is electrolytically refined now
days.  In this operation the blister copper is used as one electrode in
an electrolytic cell.  The electrolyte is mostly sulfuric acid and
copper sulfate.  The copper is electolytically transferred from the raw
blister copper to a thin sheet of pure copper which it builds up on.
Gasses and insoluble solids are not transfered to the pure copper, and
the electrolyte is designed so than non-copper metals fall to the bottom
of the tank as a sludge or remain dissolved in the electrolyte.  The
silver and gold which are usually present in copper ores are reclaimed
from the sludge.  Somebody could probably advertise audio cables made
from "100% pure electrolytically refined copper", add a paragraph or two
of techno-mumbo and sell them as well as oygen-free copper.
	Now MY interconnects, on the other hand, were personally blessed
by the Pope in Saint Peter's Square on the Feast of the Ascension.  
Ave Maria! The clarity of the highs, the richness of the bass!  The
superb definition of every sweet note in between!  I hear subtleties in
music that I never knew were there!  I finally have come home my Mother
Church after so many years astray.  Oh, you should have seen what the 
Baptists did to my power amp, and with the power on, no less.  It is 
too horrible to imagine.

			---David

	David Sherman		decvax\
	John Fluke Mfg Co.	ihnp4  >!uw-beaver\
	PO Box C9090    MS 275G		   allegra >!fluke!dms
	Everett, WA 98206 USA	ucbvax >!lbl-csam /
	(206) 356-6373		hplabs/

=====An audiophile is what I use to sharpen the needle on my record player.=====