You've got two different effects going on here. The first is the variation of cable capacitance as the you flex the cable. Some cables act like condenser microphones and change variations of capacitance into a signal voltage. The second is the degree of screening of external electric fields such as hum. Again, some cables achieve better screening than others.

Don't forget that it's usually only unbuffered piezo guitar pickups that have a really high output impedance and will give a behaviour that's anything like what you see with a cable that's not connected to a guitar.

Using a double-screen cable and joining the outer screen to the ground connection (jack plug sleeve) at one end only would be a good experiment. Try the cable both ways round, checking for hum and handling noise in both cases.

Smashh, post: 454775, member: 45856 wrote: join the earth core with the screen only at one end
to avoid a loop . Has anyone done / tried this and how was the results .?

I do have a couple instrument cables which have their shield (screen) disconnected at one end. In some circumstances they will very effectively eliminate hum, for instance, when a pedalboard with its own AC power source is connected to a guitar amp. It doesn't work in every situation, and as Boswell indicated, it is VERY dependent on which end is connected to the amp. In some cases it will make a noisy set-up worse, in some cases it's just what you need. I never use the special cables live, only very rarely when recording an especially noisy rig. Having one or two them in the kit might be worthwhile, but I use them so infrequently I'd be hard pressed to say exactly where they are. And if you make some, be sure to mark them as such, and indicate which end has the screen clipped.

Thanks for the responses . I actually bit the bullet and went to the music store and got 2 of the most expensive (lifetime warranty )
cables to do the longest runs in my gig set up , and 1 more shorter one for home when recording .
Just got home from the gig and it was a pleasure turning the amp on and wondering
if it wasl connected , then tapping the guitar strings and hearing a lovely chime .
Just thinking now about buying a couple more to cover guitar/bass set up here when recording , needless to say
Im very impressed . ,
The guy at the shop showed me the same model lead with a kill switch on one end , but I didn't go for it, as its something else
that may fail in the future .

I shall make some leads as described above for some shorter runs around the pedal board . I have all home made ,
mostly one or 2 elbow ends for desired job.

I have an uncoupled earth lead in my kit for when I was using the fx loop after the pre amp in my hotrod amp .
It works well but the downside of this is having more longer leads.
I m enjoying having my amp as far away( within reason ) as I can from where I stand on stage . Its not always possible ,
but where I can it is more enjoyable hearing the dynamics of different purchase in the room. It disconnects me from the direct sound
and helps me visualise as if I was in the audience . Id like to think it stops me from over indulging , or as my
partner says , 'stop wanking off on the guitar ' ! .....

dvdhawk, post: 454782, member: 36047 wrote: I do have a couple instrument cables which have their shield (screen) disconnected at one end. In some circumstances they will very effectively eliminate hum, for instance, when a pedalboard with its own AC power source is connected to a guitar amp.

I'll try that too.. I never know what customers bring to a session..

I have about a 30' run from my live room to the iso booth where I usually set up the amp. Running unbalanced 1/4" cables that far is no good. My solution is simple and effective: I plug the guitar into an active DI. I take the low-impedence, balanced XLR output and run that into my XLR snake that patches through to my iso booth. I then take that low-impedence, balanced XLR and plug it into a passive DI (using an XLR gender changer), and take the unbalanced 1/4" TS output and plug it into the amp. Problem solved! Try it!
~Jeff