STOO-PID question........

[Bucksears]

Ok. Apparently I need to use shielded wire for some of my pedals. I have some, used it one time about 6 yrs ago, but haven't used it since.

How does one use shielded wire properly? Use the internal (center) wire for the connection, but connect the external braiding to ground? And what does connect 'one side' to ground mean? Expose and ground the braid on one end of the wire but not the other? If all of this is true, doesn't that lead to a lot of extra wires running around?

As always, thanks,
- Buck

[aron]

It's not stupid and you answered all your questions.

Usually you just shield the input wire and output wire (if necessary).

[Mark Hammer]

You would be surprised about how many commercial pedals do not use shielded cable inside.  Jeez, I'd venture to say at least 98% of them.  Of course, in a great many of these cases, the board may be custom designed to suit a custom chassis, using PCB-mount pots and/or jacks, so the possibilities for stray signals are greatly reduced.  The rest of us mere mortals may find ourselves in the tricky position of having to situate a pot or switch somewhere that is practically an embossed open invitation (complete with RSVP envelope) to hiss, noise, buzz and unwanted oscillation.  In such instances, shielding IS a good practice, though obviously it can be awkward to use shielded cable in such a small working space.

Certainly, if you ever have a high gain device, and the leads to and from pots or jacks get uncomfortably close, using shielded cable is a smart idea.  Of course, once a risky situation is identified, that does not mean that shielding is needed absolutely everywhere.  For instance, suppose you make the standard high gain fuzz/distortion pedal, and build it into a Hammond 1590B chassis (the little box used by MXR/Dunlop, Z-Vex, Keeley, and countless others).  Chances are pretty good the path from the jack to stompswitch will be something like a 1-2" piece of wire, situated away from the circuit itself.  No shielding really needed there.  Same goes for the output jack.  Now, were the circuit in a different box and the jacks located beside each other, or perhaps the wire from the jack had to run really close to the parts of the board where the output signal was running really close to the input signal, shielding would be VERY useful.  Similarly, if the output jack was right near the gain pot such that stray signal could find its way to become part of the input to the gain stage, once again shielding would be called for.  

Very often, shielding EVERYTHING is not necessarily required.  For instance, shielding the wires to the jacks may reduce the need to shield the leads to the pots or switches, and vice versa. Obviously, more insurance is more insurance, but often once you've shielded some critical elements, you've gone most of the distance.

As well, most pots and switches will be grounded to the chassis, in which case the braided shield doesn't HAVE to be soldered to the board.  You can simply connect the internal cable (inside the braid) to the board, and connect the braid to the pot in a way that makes a ground connection.  Given how clumsy it can be to find a ground connection on the PCB for a braided lead (without grounding out the leads of nearby components), this can be a lifesaver.  It is not "ideal", but again you'd be surprised to see how often this is used by commercial manufacturers in pedals/devices that are fairly noise-free.