AW: To earth, or not to earth...

[Ingo Debus]

Martin Czech wrote:
> Only if signal ground is connected to chasis ground.
> This is not always needed.

I believe you're right, but...

>   And class I means: Chassis
> ground to supply earth, i.e. all conductive parts that can be touched
> by the user, even potis, if there are metal.

No doubt a metal 1/4" plug can be touched by the user. Even the plug's
tip at the other end of the cable can be touched. Surely the tip cannot
be connected to PE. I'm a bit confused...

> > If there is such a regulation, what about laboratory power supplies?
> > They always have earthfree outputs.
> They are for "expert use" only.

I've never seen anything like "expert use only" printed on a power
supply. The Yamaha DX7II has no connection between signal groung and PE,
too.

> > If there is not, why do so many manufacturers implement this connection?
> You mean class II. See above.

No, I mean class I. A connection between signal ground and PE is only
possible in class I devices, since class II doesn't have PE.

Ingo