Tube modular vs. safety

Martin Czech martin.czech at
Thu Nov 25 09:59:35 CET 1999

:::I remember a ditzy secretary/receptionist when I was
:::working in an earlier life as an investment analyst
:::(in the 60s) who would idly suck on the end of the 
:::phono plugs in the antique switchboard, get a 50v 
:::boot thru her fillings, burst into tears, and get the 
:::rest of the day off.

Hahahaha ...

That's the reason why strings etc. of  guitars tied to signal
ground which is in turn tied to protective earth. This way the
guitar can never be a shocking experience, no matter what happens
to the input triode grid/resistor/wires. I check this from time
to time, could be a nasty surprise.

I often notice, that floating chassis, or floating gnds of supplys
(versus protective earth) have an undesireable "feature"
If you touch them very softly, you can feel the capacitive hum in
your finger tip, this goes away if you get more grip, because
I think this shortens the chassis capacitance to the hot wire.

Is it just me, or did you notice this too?
Not harmfull, but unpleasant. Some lamps I have do this.

I wouldn`t like a metal synth chassis to have this, so better
protective ground the chassis, and maybe wire a resistor (1k or so)
from signal ground to protective earth.


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