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From: michaelk@copper.UUCP (Michael Kersenbrock)
Newsgroups: net.audio,net.analog
Subject: Re: need interconnect cable recommendations...
Message-ID: <477@copper.UUCP>
Date: Mon, 14-Jul-86 00:16:50 EDT
Article-I.D.: copper.477
Posted: Mon Jul 14 00:16:50 1986
Date-Received: Tue, 15-Jul-86 05:55:13 EDT
References: <2107@orca.UUCP> <926@ihu1g.UUCP> <1225@uwmcsd1.UUCP> <328@argus.UUCP>
Reply-To: michaelk@copper.UUCP (Michael Kersenbrock)
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Organization: Tektronix, Inc., Beaverton, OR.
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Xref: watmath net.audio:8973 net.analog:943

In article <328@argus.UUCP> ron@argus.UUCP (Ron DeBlock) writes:
~
>1) Just how important is the skin effect at audio frequencies?  Audio is
>pretty low on the spectrum, I wouldn't think it would be that big of
>a problem.

Not much.  My 12-gauge speaker wires (with 4-ohm speakers) has a small
bit of impedance increase starting at about 40,000 Hz.  That still is
"wiped out" by the DC-resistance of my wire.

>
>2) What about impedence mismatch?  With a 75 ohm transmission line connected
>to a 4 or 8 ohm load, I would expect quite a bit of reflected power.  Or
>doesn't that matter at audio frequencies?
>

The "characteristic impedance" of a transmission line assumes that your
interconnect is long enough to be a transmission line.  The turnover
point (where transmission-line effects start to "work") was something
like lambda/20  depending upon how much effect you decide
is effect (and depending upon how good my memory is).  This is
not significant anyway.  If we assume the point is lambda/50, (where
lambda is the wavelength) then (assuming a 0.66 velocity factor),
lambda at 30,000 Hz is about 21,000 feet.  So even using generous
numbers you still need your cable to be at least 400 feet long for
a miniscule effect at 30Khz.


-- 

Mike Kersenbrock
Tektronix Software Development Products
Aloha, Oregon