[OT, but important] GND lift how to do and the dangerous

Ralf Mardorf ralf.mardorf at alice-dsl.net
Sun Jan 9 19:06:50 UTC 2011


Hi :)

on another thread ground lift was a topic. IMO we should use ground lift
if needed, but also be aware that it needs care to be safe when using a
ground lift.

At the moment I don't have time for research, I did a quick search on
German and found this interesting thread that might be mistaken:

http://www.hifi-forum.de/viewthread-29-11350.html

To keep the translation short, here it's said that 50V~ and 120V= are
dangerous.

On the physikerboard.de I've got the nick Legastheniker and I quoted a
book about VDE:

http://www.physikerboard.de/ptopic,3766.html#3766

The book said that ex 60V= and ex 25V~ are dangerous.

1.

For shielding GND lift is insane, it will reduce ground loop, but
increase anything that has to do with shielding, as digital electric
smog. Sending and receiving electric smog depends to the shielding, not
only to one of both.

2.

GND lift for power supplies is another issue, while ground loop will
reduced or eliminated it, this could be dangerous.

It would be nice if we could talk about this OT, because it would be
nice, if nobody of us will be killed, just because we are mistaken
regarding to ground lift methods.

Again, IIRC the Brauner VM1 power supply does use a capacitor only,
anyway this might not be a good solution.

Any hints are welcome!

Regarding to digital noise by electric smog, IMO we should think about
better shielding. Again, perhaps the method to connect unbalanced
instrument outputs to balanced (single sided shielded) mixer inputs
might be one solution. FWIW, the DI box of my Peavy KB-300 doesn't
eliminate noise. Galvanic isolation isn't a guaranty to eliminate noise,
just safe regarding to other issues.

Before using a ground lift I would check if everything is connected to
the same power feed etc., sometimes it helps to turn the power supply
plugs in the sockets, perhaps because at least in Germany neutral is
connected to ground.

Ralf




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