Shielded wire grounded at one end

[Johnrcurry]

I've seen drawings that show a shielded wire from the input jack and/or the volume control to the preamp tube, with one end of the shield grounded and the other end insulated. Sometimes I see the shield grounded at the input/pot end. Sometimes I see the shield grounded at the tube socket end. Is one way better than the other, or does it not matter?

Thanks

[raiken]

A shield grounded at only one end is called a "telescoping shield". It is used to prevent ground loops and noise, because there can be no current flowing through the shield, so it acts only a screen against interference. It is usually grounded at the source end, or the lowest impedance side.

RA

[Johnrcurry]

Thanks. Does that mean ground the input jack end for an input jack, and the pot end for a volume pot?

John

[R.G.]

Thanks. Does that mean ground the input jack end for an input jack, and the pot end for a volume pot?

The rule of thumb for shields is to ground the quiet end. Usually this is the lowest signal end.

[Johnrcurry]

Thanks.

[Wilder Amplification]

When you do up a shield this way, the shield is not part of the circuit and is essentially acting as an extension of the chassis.

I typically ground the "input" end of the shielded cable and I always go directly to the chassis via a solder lug.