Tech: Guitar cables - wired wrong way round ?

Subject: Tech: Guitar cables - wired wrong way round ?
From: GUEST,Marshall Roland
Date: 11 Jul 14 - 01:18 PM

Guitar cables - eg. 10ft premium quality.

If one end had been mistakenly wired the wrong way round by the manufacturer, would:

a] no signal pass through ?

b] normal volume signal pass through ?

c] a weak signal pass through ?

d] if b or c, would tone be affected - either dark and muddy, or thin and trebly ?

cheers.

Subject: RE: Tech: Guitar cables - wired wrong way round ?
From: Sandy Mc Lean
Date: 11 Jul 14 - 01:36 PM

If co-ax (shielded single conductor) it would ground out and kill the signal. A two conductor balanced cable would work either way but it would change the phase 180 degrees.

Subject: RE: Tech: Guitar cables - wired wrong way round ?
From: ripov
Date: 11 Jul 14 - 02:16 PM

Yes, the signal from two core balanced cable (but is this configuration used?) would not be affected, but neither would that from single screened cable if the jack socket is only connected to the pickup. If other metalwork (like control mounting plates) were bonded to the sleeve connection of the socket this would make the set-up very suceptible to hum.
Presumably these are being offered at a bargain price. How did these cables get out of the factory? And are there any other potential manufacturing faults?
If they're otherwise ok, you could rewire the plugs, or fit new.

Subject: RE: Tech: Guitar cables - wired wrong way round ?
From: GUEST,Marshall Roland
Date: 11 Jul 14 - 02:24 PM

Thanks - for better clarification; standard good quality guitar cable with jack plug at each end.

Subject: RE: Tech: Guitar cables - wired wrong way round ?
From: Sandy Mc Lean
Date: 11 Jul 14 - 09:45 PM

If a single conductor cable is reversed on one end it would create a dead short to ground. This would not be created at the pickup end but at the mixer or amp where the sheath would be bonded to earth. However if it is fed through an isolating transformer what ripov says could happen. An open sheath would be a hum magnet for sure. The phase mis-match could create a signal in opposition to another mixer input from other instruments or mikes.

Subject: RE: Tech: Guitar cables - wired wrong way round ?
From: GUEST,BobL
Date: 12 Jul 14 - 04:25 AM

If the signal is mixed with others from different sources, the phase-reversal won't make any difference. It will only matter if it's mixed with an un-reversed copy of itself, and I can't see that happening in any normal setup.

AFAIK guitar cables are single-cored coaxial, and the design of the plugs makes it pretty well impossible for them to be miswired by mistake. It's easy enough to check them though. With a metal plug, just unscrew the casing and have a look, but if it's moulded then a battery and bulb is all the test gear you need.

Subject: RE: Tech: Guitar cables - wired wrong way round ?
From: ripov
Date: 12 Jul 14 - 11:38 AM

Sandy, I'm sorry but I can't see where your short circuit occurs. Surely either the centre conductor goes to the signal input of the amp and the screen to amp ground in the normal way, or vice versa in this reversed plug scenario? The screen shouldn't be grounded anywhere else, and the centre conductor certainly will not be.

Subject: RE: Tech: Guitar cables - wired wrong way round ?
From: GUEST,Marshall Roland
Date: 12 Jul 14 - 12:44 PM

Thanks for responding - good, you folks know what your're talking about at a fair expert level.

It's all above my head, I've never managed to retain any understanding of impedance, capacitance, ohms and such like.

So, I'll now expand on why I opened this thread.

[cable wired the wrong way at one end was just one possible idea that occured to me]

I've just bought a new mail order mass produced premium 'standard jack to jack' guitar lead [one of the big brand names]

There's definitely something amiss with it, but no obvious faults like crackle
or intermitent signal brak up and loss if I wiggle the jacks in their sockets,
or waive the cable around.

Compared to all my other decent quality guitar leads,
this new one has a very weak signal level and dark tone.
Similar to what you'd hear with an electric guitar's vol and tone knobs rolled right down. Very severe vol and treble cut-off !!!

I've tested with a couple of guitars and amps.
eg, 4 watt Vox combo valve amp - all knobs on 12 oclock / strat type guitar - tone & vol knobs on 10.

Normally this would be anti social bedroom practice vol level.
At this setting, the new lead is barely audible.
But as I said, no crackles or signal break up ?

I phoned the manufacturer's helpline, and they said this isn't right,
so they're sending another so I can compare for them
to help investigate - very positive result - good customer service..

But this is where it get's interesting, because as this 'faulty' lead is acting as some kind of vol & tone attenuator,
I can now push the amp to full volume,
and get a pleasing smooth vintage tone without any ice pick treble,
at a sensible home practice level ???

So even if it is a 'dud' - it's a keeper.

It'd even be interesting to know how to replicate this 'fault' deliberately ?

Also of relevance, if the dodgy new lead is plugged between electric guitar and a true bypass overdrive pedal
[ and a good working lead from pedal to amp]
the signal hitting the amp is still weak and dark.
However if the the leads are reversed. Good lead now from guitar to pedal,
and dodgy new lead from pedal output to amp.
The signal is now mysteriously restored to near normal level ???

Hope this is an interesting enough problem for you folks to get your teeth into...
cheers...

Subject: RE: Tech: Guitar cables - wired wrong way round ?
From: GUEST,Marshall Roland
Date: 12 Jul 14 - 12:48 PM

Forgot to mention - whatever is wrong with this cable,
it is not introducing any noticable extraneous hum or buzzing into the signal chain.

Subject: RE: Tech: Guitar cables - wired wrong way round ?
From: Greg F.
Date: 12 Jul 14 - 03:43 PM

Suggest you have someone put an ohm meter on it & check both braid(shield) & center conductor ( and/or tip & ring on the plugs )- may be a cold solder joint or other problem introducing resistance that shouldn't be there into the cord resulting in the attenuation you describe.

Subject: RE: Tech: Guitar cables - wired wrong way round ?
From: GUEST,Marshall Roland
Date: 13 Jul 14 - 10:49 AM

cheers Greg F,
I've got to admit a deficiency, I never learnt basic electrics - how to solder, or even use meters - depite playing for 40 years.

I really should do some youtube tutorials..

So, do you all concur with Greg's diagnosis, or have further ideas ?
I'll be phoning the cable brands product support again sometime soon.
so need to be properly informed and prepared.

I'll tell you why this is of greater interest to me.
Presently I own a few hundred pounds worth of power attenuators for connecting between valve amp heads and speakers.
This helps give fairly ok power valve tone at much reduced volume levels.

Not the most convenient set up for simple quick n easy home practice.

I can plug an overdrive / clean boost / etc FX pedal into a small combo amp
- push the amp vol up, while keeping the pedal output very low.
Buit it's not ideal.

So the idea of a properly tweaked product like an effective inexpensive 'attenuator' guitar cable - if it could exist in practice -
is actually quite apealing.