lifting the earth

[Jaap]

I have sometimes seen that people use a small resistor or a diode between earth of the amplifier and the chassis.
What is the purpose of this ?

 

[Miles Prower]

Helps break ground loops to get PS noise out of the signal path.

 

[Jaap]

Thanks, I suppose tyhe value of that resistor is not critical. 100R ?

 

[athos56]

Dosn't seem to, I throw in any small value I have laying around.

 

[tomchr]

When taking a Parasound A23 apart, I noticed that their ground lift switch implements the ground lift by capacitively coupling signal ground to chassis ground through the parallel combination of 100 nF and (I think) 10 uF. The goal here is to create a high impedance between the two grounds so no current flows. You want some impedance there to avoid HF instability and/or EMI issues, hence, the use of a capacitor.

~Tom