Coax cable vs. balanced twisted pair for guitar

[Pushtone]

I was showing my YingYang pedal (Combination EFX loop and amp footswitch) to a guitar tech for a major touring band.
http://www3.telus.net/david65/pedal-pics/YingYang-SM.JPG

He told me its a bad idea to use twisted pair cable for unbalanced guitar. Only coax cable should be used he insisted, although he didn't say why. The YingYang pedal uses two channel (2 pair) balanced mic snake cable. The same type of cable found in microphone snakes. One pair is for the guitar signal, the other for the amps footswitch jack that controls reverb on/off and channel switching.

Can anyone confirm this and tell me why only coax cable should be used for guitar? Needless to say he didn't like my pedal very much.

[Eric H]

I was showing my YingYang pedal (Combination EFX loop and amp footswitch) to a guitar tech for a major touring band.
http://www3.telus.net/david65/pedal-pics/YingYang-SM.JPG

He told me its a bad idea to use twisted pair cable for unbalanced guitar. Only coax cable should be used he insisted, although he didn't say why. The YingYang pedal uses two channel (2 pair) balanced mic snake cable. The same type of cable found in microphone snakes. One pair is for the guitar signal, the other for the amps footswitch jack that controls reverb on/off and channel switching.

Can anyone confirm this and tell me why only coax cable should be used for guitar? Needless to say he didn't like my pedal very much.

Twisted-pair mic cable --is-- coaxial, because of the shield that surrounds the main conductors (which shoud be grounded). He probably didn't like the last foot of cable on those two connectors that is unshielded. You should re-work that part of your design so the entire path is shielded.



-Eric

[Hal]

balanced relies on opposite phase to cancel interferance.  Shielding doesn't.

[niftydog]

Crosstalk can be an issue, especially when using 1 twisted pair to run two dissimilar signals such as an audio signal and a switching signal.

Although, coax is sometimes overkill. Every Boss pedal I've ever seen just uses hook up wire for the whole thing!

[Eric H]

balanced relies on opposite phase to cancel interferance.  Shielding doesn't.

This is clearly not a balanced application.

[George Giblet]

> Every Boss pedal I've ever seen just uses hook up wire for the whole thing!

It depends what type of interference you are trying to get rid of.  Boss pedals use a metal enclosure so the whole enclosure forms a shield around the circuit and prevents  external interference getting in.    If what is inside the box is noisey, or you don't want some parts of the circuit coupling to other parts,  then using coax inside can prevents this.


Running twisted pair for a guitar doesn't achieve anything (in fact it's probably detrimental).

With certain pickups you can run differential preamps *inside the guitar* with good results but once the signal hits the unbalanced volume control and output socket you are better off with coax.

[DDD]

Microphone cable actually is not coaxial. Coaxial means that both central conductor and shielding braid have the same axis line. Twisred pair conductors have no straight axis :-)
I use shielded microphone twisted pair for my guitar. It's a result of numerous experiments and experience.
Please note: the cable should be arranged as following:
- first conductor (usually red one) is to be soldered to the central contact of a plug
- second conductor (usually white)  is to be soldered to the "ground" contact of a plug
- braid should be soldered to the "ground" contact of a plug ONLY AT ONE SIDE of the cable.
Such an arrangement means that both internal conductors of the cable are "signal conductors", and braid is only "shielding conductor". So signal current and possible interference currents are separated, thus providing less noise\interference.