whirlwind accusonic+1 hi-z cable shorting

[VanGenz]

I bought a roll of this cable many years ago and have used it for making "guitar cables-jack/jack" of different lenghts. After some use a strange halfway shorting problem sometimes occurs. I have a 1 meter cable now that when testing with a Behringer CT100 (which is very good with the "intermittent" leds that can be reset) shows full short, and when I meassure with an ohm-meter shows 2,5kOhm between tip and ground. This cable still works with active guitars but kills a passive guitar. I am an experienced electronic builder/repairman and have been soldering for more than 50 years. I can not see anything wrong inside the jacks and when I made the cable it meassured ok. I have experienced this with quite a few cables. Anyone that have seen similar problems with this kind of cable?

 

[JohnRoberts]

If you have a whole roll of that cable how does it measure unused?

2.5k is clearly faulty... can you troubleshoot to determine if it is a single fault, or the entire cable. For example cut a bad cable in half and see if the low impedance stays with one end.

JR

 

[Khron]

Well, 2.5k between what should be two isolated conductors is pretty close to a dead short. Especially considering that passive pickup output impedances range between 5-20k, you end up with quite the attenuation if you load that with 2.5k to ground.

 

[mjrippe]

I did not look up the cable, but make sure it does not have a conductive plastic shield. This has caused many headaches in the past because it does not look like a conductor but it will cause intermittent and short readings.

 

[JohnRoberts]

+1

IIRC there were even some guitar plugs designed to shunt from tip to sleeve with a modest resistance when unplugged to prevent hum from an open cable. Of course 2.5k is too low impedance for not loading down a lead guitar pickup when plugged in.

JR

[edit- Whatever you do, DO NOT connect mains voltage (240VAC) across that cable so the 2.5k impedance will generate tens of watts of heat, revealing itself. Absolutely positively DO NOT do that.... /edit]

 

[Khron]

According to the bulk cable's manufacturer page (no datasheet as such), the conductor-to-braided-shield insulation should be polyethylene (PET), so no fancy / conductive stuff.

 

[transient]

I did not look up the cable, but make sure it does not have a conductive plastic shield. This has caused many headaches in the past because it does not look like a conductor but it will cause intermittent and short readings.

I have made many cables using Accusonic+1, some still in professional use after 15 years. Yes, it does have a conductive plastic layer. I always test new cables with my 500 volt insulation tester - this gives readings >50 Gohm.

 

[VanGenz]

I have made many cables using Accusonic+1, some still in professional use after 15 years. Yes, it does have a conductive plastic layer. I always test new cables with my 500 volt insulation tester - this gives readings >50 Gohm.

I suspected something like this could cause this. I fixed the 1 meter cable yesterday. Took a chance and cut 10mm from one of the jacks. The shortage was gone, both in the jack with just 10mm cable and the one with 1 meter cable and a jack in one end. Soldered the same "old" jack to the cable and it meassured ok. Tried to fix a 5 meter cable with the same problem but here the problem still was there after cutting away both jacks and soldering one of them back. Do not have more of this cable left and will not buy it again. I am a gigging musician and almost every time I have experienced intermittent or permanent problems this cable has been the problem. I wonder if the strain relief can cause this after a while.

 

[VanGenz]

I need to buy 50 or 100 meter cable of equal quality without the conductive plasic layer. I have mounted Neutrik NP2RX-Silent (angeled jack with switch) on a lot of these cables. I play different acoustic (active) instruments live and love these Neutrik plugs. Any suggestions of a similar cable for this use? I can buy from Farnell, they have a lot of both cheap (their own brands) and more expensive like Belden.

 

[Newmarket]

I need to buy 50 or 100 meter cable of equal quality without the conductive plasic layer. I have mounted Neutrik NP2RX-Silent (angeled jack with switch) on a lot of these cables. I play different acoustic (active) instruments live and love these Neutrik plugs. Any suggestions of a similar cable for this use? I can buy from Farnell, they have a lot of both cheap (their own brands) and more expensive like Belden.

Be aware that the 'semi conducting' plastic layer is there to reduce electrical noise caused by cable movement when used with High Impedance sources - esp passive guitar pickups and piezo transducers (if there's no internal preamp).
If using cable without this it can often be better for choice to use a standard twisted pair mic cable and use one of the pair to double up on the 'ground' connection.

 

[Whoops]

Any suggestions of a similar cable for this use?

I like KLOTZ LaGrange GY107 Low Capacitance Instrument cable, it's the only cable I buy for instrument use.
Besides that I would only go for top brands like Van Damme, Gotham cables, Belden, Cannare, Mogami

 

[Khron]

... Or Cordial?

 

[abbey road d enfer]

... Or Cordial?

Indeed.
Specs are impressive.

 

[Newmarket]

I like KLOTZ LaGrange GY107 Low Capacitance Instrument cable, it's the only cable I buy for instrument use.
Besides that I would only go for top brands like Van Damme, Gotham cables, Belden, Cannare, Mogami

Seems that is now 'replaced' by AC110sw although basically the same thing.
unbalanced hifi audio cable

Anyway - just wanted to point out (in general) that it has the semiconducting layer that's basically required for trouble free Hi-Z transducer use. You just have to be sure to cut that layer back and ensure it makes no contact with the signal conductor.

 

[Whoops]

... Or Cordial?

I don't think Cordial is in the same quality range as the other companies I suggested, but I may be wrong...

 

[VanGenz]

I am a little embarrassed it took me 15 years to figure this out. Took me 15 minutes to fix 8 cables today. With a scalpel I cut away the conducting layer around the centre signal wire and everything was ok. Enclose "before" and "after" pictures. Thank you all for professional assistance!

 

[cyrano]

Well, I'd never even heard about a semi-conducting layer in audio cables either, so...

 

[abbey road d enfer]

I believe almost everyone here has had the same issue. Once I found the solution I could brag about it and snigger at the poor souls who were in perplexity.

 

[JohnRoberts]

This is the benefit from our community sharing our collective experience... As a large diverse group, we've already made most common mistakes, and some of us have learned from those experiences.

Even better when we can learn from other's mistakes.

JR