Cable Shield Conducts

From detritu–(at)– Sun Nov 25 20:19:04 CST 2001
From: Lord Valve
Newsgroups: alt.guitar.amps
Subject: Re: Guitar cable/severe attenuation…WHAT’s Up???????
Date: Sun, 25 Nov 2001 15:27:32 -0700
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Xref: alt.guitar.amps:371498

MBarnett wrote:

> “j.k.” wrote:
> > I bought some Horizon Studio-1 bulk guitar cable. I bought 2 straight
> > 1/4″ switchcraft plugs to solder onto the ends.
> >
> > The cable itself is about 20 feet and I soldered on the plugs and I
> > have what definitely appears to be nice clean soldering.
> >
> > So I plug it into the ‘ol Marshal hi-gain amp and WOW!…the sound is
> > severely attenuated. I have the gain cranked and it sounds like a
> > very mildly clipping sound. Low noise, but no full guitar output into
> > the amp.
> Have you measured the resistance or done a continuity check of the
> cables? I ran into an interesting problem hacking up a Peavey cable into
> several shorter ones a few months back: Seems there was a conductive sleeve
> (black) on the outside of the center conductor’s insulation (translucent
> white). If ANY of that black sleeve came in contact with ANY of the center
> conductor, I had a short (either direct or high-resistance) to the shield.
> Once I realized I was dealing with some “new-fangled” cable, I just trimmed
> the conductive sleeve back and all was right with the world. (Or at least
> with my cables!)
> Monte

Lord Valve Speaketh:

OK, Monte nailed it. The “black sleeve” around the
center conductor is an electrostatic shield; cable
designed expressly for guitar use usually has this.
In some cases, it’s conductive plastic (Canare, Mogami)
and in others it’s cloth (Belden and other “old school”
wire makers). You *must* remove this when making
cables. The cloth kind is easiest to deal with, because
you can force the tip of an awl (or similar tool) between
the cloth and the center conductor’s insulation, and then
rip downwards, cutting the sleeve off with your nippers
when you reach the point where the center conductor
enters the braid. For the plastic type, I like to gently
bite it with my Miller 103-S strippers (any pro-quality
strippers will do; the Miller is the kind I like) and just
strip it off like insulation. Doing it like this takes a
little experience, since it’s important not to nick the
insulation underneath. Once you have the electrostatic
shield removed, you can just solder the cable in the
regular fashion. The electrostatic shield is a high-
resistance conductor, which is why you get attenuation
when it touches the center conductor; it’s exactly the
same as connecting a resistor between the shield
and the hot lead. The reason this shielding is there
is to keep the cable from making skritchy-scratchy
noises and thumpy-slithery sounds when it slides
around on the stage. Many a rookie has decided
to make himself up a guitar cable out of some leftover
mike wire and found out the hard way that lo-Z cable
doesn’t work worth a shit in that application. Miles,
I believe I have an old post I saved dealing with this;
I’ll shoot it to you and you can decide whether it
should reside in the AGA FAQ. No fair peeking,
Glum…you *know* there isn’t anything worth reading
on the AGA site…right? 😉

Lord Valve
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