Solid State Guitar Amp Forum | DIY Guitar Amplifiers

I have a couple of basic questions regarding the use of shielded cable within an amp. Here goes.

1) Which end of the shield should be grounded? I know this is a generic question but I'm struggling with it. I know I should only ground one end of the shield to avoid ground loops, but which end? Lets say I'm running a shielded wire from my preamp board to a volume pot. Should the shield be grounded at the pot or at the board?

2) How many leads for a mono 1/4" audio jack? Since the barrel of the 1/4" plug is ground, can I just connect the shield and use a single conductor inside for the signal (tip)? Or, would it be better to run two-conductor shielded wire from the jack to the preamp board with the ground and signal on shielded conductors with yet another connection to ground for the shield itself?

Thanks for any advice.

-Matt

Anyone?

Quote from: armstrom on September 08, 2008, 10:37:34 AM


1) Which end of the shield should be grounded? I know this is a generic question but I'm struggling with it. I know I should only ground one end of the shield to avoid ground loops, but which end? Lets say I'm running a shielded wire from my preamp board to a volume pot. Should the shield be grounded at the pot or at the board?

I tend to ground at the board, but it doesn't make any real difference. I'd go with whatever you find convenient.

Quote
2) How many leads for a mono 1/4" audio jack? Since the barrel of the 1/4" plug is ground, can I just connect the shield and use a single conductor inside for the signal (tip)? Or, would it be better to run two-conductor shielded wire from the jack to the preamp board with the ground and signal on shielded conductors with yet another connection to ground for the shield itself?

Just connect the screen to the barrel and the core to the tip. That'll work just fine. Try to ensure that the jack is isolated from the chassis to avoid ground looks though. The plastic sockets are best for this.

Rgds

Martin

Shield may grounded wherever it is easiest for you , keep leads as short as possible, watch lead dress, and try not to cross supply lines with signal lines if possible. AS far as 1/4 input jacks go I use 2 conductor shielded and unshielded , in most cases it is rather unimportant.

                                       Rock On

And this:  if you are running a wire and just want it shielded, then ground one end somewhere.  But if the shield is also a ground connedction then both ends are connected.  An example of that is the guitar cord.  the shield is ALSO the ground return.  SO if you have a remote pot such as your example of a pot wired down to a preamp board, and there are the hot and wiper wires, if the shield serves as the ground for the pot too, then both ends are connected.  If the pot is just grounded to the panel, then one end is enough.