[sdiy] Tubes in Synths [ was : Harry's Nightmare! ]

[Ingo Debus]

harry wrote:
> 
> We are talking REALLY tiny... the glass would stop it cold. Now if
> you were to chew on one of them... you'd cut yourself...
> 
> H^) harry
> 
> John L Marshall wrote:
> 
> > I check five reference books, there was no mention any radioactive additive
> > in zero tubes. The amount added to neons is not enough to be concerned
> > about. Worry about all the fat in the brautwurst. The fat tastes sooo good.
> > Doesn't your 0C3 look really cool?

Harry and John (and Doug too, who replied privately), thanks for
clarifying. I was a bit worried because this amp is from the fifties or
sixties, when people weren't so worried about radiation as they are
today. As I bought it about 10 years ago, I thought it was a tube
rectifier and it sure would go bad soon because of the bright glow.

Next question is, why did they use this tube? Looking at the schematic
(it's attached to the side of the amp chassis), it is used to drop the
405 volts to 300 volts for the power tubes' grids. The 0C3 is in series
with the power supply, not like a shunt regulator in parallel with the
load. Why didn't they use just a resistor divider?
>From there the 121 volts supply for the preamp stages is derived,
through a 10k resistor.

Ingo