• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Question regarding 3rd wire grounding and safety

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Bitrex

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Joined 2009
#1
I'm wondering, when one connects the 3rd wire ground to the chassis of an amplifier to prevent the chassis going hot in case of a fault, doesn't this negate the safety benefit of floating the secondary of the primary transformer from the line side? Since the chassis is grounded at the IEC connector on the primary side, and probably through the input/output jacks on the secondary side, I would assume that it is now possible to be shocked just by touching the amplifier B+ or B- supplies and some grounded object, instead of having to touch both sides of the secondary transformer that's completely floating. Is this correct?
 
#2
If I understand the question, yes. Although the HV secondary in the power transformer is center tapped or bridged from ground anyway. So the safety ground is not needed to get shocked while touching the B+ and the chassis.
 
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