lifting the earth

Jaap · 23rd November 2009, 09:11 AM

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 · 23rd November 2009, 09:14 AM

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

Jaap · 23rd November 2009, 10:23 AM

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

athos56 · 23rd November 2009, 02:05 PM

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

tomchr · 23rd November 2009, 07:03 PM

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

23rd November 2009, 09:11 AM	#1
Jaap diyAudio Member Join Date: Dec 2002 Location: Netherlands	lifting the earth 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 ?

23rd November 2009, 09:14 AM	#2
Miles Prower diyAudio Member Join Date: May 2005 Location: USA Blog Entries: 6	Helps break ground loops to get PS noise out of the signal path. __________________ There are no foxes in atheistholes www.dolphin-hsl.com

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23rd November 2009, 10:23 AM	#3
Jaap diyAudio Member Join Date: Dec 2002 Location: Netherlands	Thanks, I suppose tyhe value of that resistor is not critical. 100R ?

23rd November 2009, 02:05 PM	#4
athos56 diyAudio Member Join Date: May 2006 Location: Yakima, Washington	Dosn't seem to, I throw in any small value I have laying around.

23rd November 2009, 07:03 PM	#5
tomchr diyAudio Member Join Date: Feb 2009 Location: Greater Seattle Area	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