Pre-Amp earthing concern

bizbad · 9th September 2011, 08:49 PM

I am building a pre-amp with an external wall transformer. It is a 16v ac transformer without the third terminal for earth ground. I have seen others with this configuration but never wondered about earthing. Is earthing necessary on the pre-amp and if so, how is it done?

sofaspud · 9th September 2011, 10:02 PM

No, you don't need an earth ground.

AndrewT · 10th September 2011, 10:50 AM

If the wall mounted power supply is rated "double insulated" and carries the two concentric squares symbol, then anything downstream that is powered by that ClassII supply is safe to use without additional PE to case earthing.

However, if that pre-amp has exposed conductive parts and it is connected to some other apparatus that does not meet the ClassII standard, then there remains a risk of electric shock if the other apparatus goes catastophically faulty.

bizbad · 11th September 2011, 02:38 PM

Thanks, I am good to go then.

9th September 2011, 08:49 PM	#1
bizbad diyAudio Member Join Date: May 2010	Pre-Amp earthing concern I am building a pre-amp with an external wall transformer. It is a 16v ac transformer without the third terminal for earth ground. I have seen others with this configuration but never wondered about earthing. Is earthing necessary on the pre-amp and if so, how is it done?

9th September 2011, 10:02 PM	#2
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio TX	No, you don't need an earth ground. __________________ It is error only, and not truth, that shrinks from enquiry. - Thomas Paine

10th September 2011, 10:50 AM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	If the wall mounted power supply is rated "double insulated" and carries the two concentric squares symbol, then anything downstream that is powered by that ClassII supply is safe to use without additional PE to case earthing. However, if that pre-amp has exposed conductive parts and it is connected to some other apparatus that does not meet the ClassII standard, then there remains a risk of electric shock if the other apparatus goes catastophically faulty. __________________ regards Andrew T.

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11th September 2011, 02:38 PM	#4
bizbad diyAudio Member Join Date: May 2010	Thanks, I am good to go then.

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