Cgs synth

>If you need extra VCA's *and* want to enrich your harmonic output,
>this may be the ticket. Of course, it may also force you to enrich
>your power supply requirements. Right now, I'm using a separate
>triple-output supply (+&-15 and +5vdc)for just the planned triple
>tube VCA. This would probably be better done with a separate 5 volt
>filament supply and a much larger dual-output supply for the synth's
>15 volt requirements. The present method will require me to isolate
>my tube VCA grounds from the rest of the synth modules to avoid
>ground potential hum. Hmmmmmmm....

Don't isolate your grounds - it can cause potential build up between
modules. What I do is make sure the metalwork of the PSU is grounded to the
mains ground, but ensure that the 0V line is isolated from ground. I then
put a 1k 2W to 5W resistor between the 0V line and the case ground. This
keeps the 0V line from jacking itself up, and prevents hum loops. Of course
you will need to make sure the PSU is not bolted to a common metal chassis
with the other supplies.

Ken
_______________________________________________________________________
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Good advice Ken! Thanks again. That's pretty much the scheme I
envisioned, but the 1K resistor is a good idea.

The 6064 tube does very well with the 15 volt plate supply. Would
the sheet beam tubes perform this well?

Chub-feeling less isolated

>The 6064 tube does very well with the 15 volt plate supply. Would
>the sheet beam tubes perform this well?

Now that I don't know - howver, if you were to add a decoupling capacitor in
the input lead to the beam modulators, you could run them from +15 to -15
(instead of +15 to GND) and that would give you 30 volts to play with
instead. The plate resisitors would need to be reduced too. I still don't
know if it would work. I've thought about if often enough, but haven't had
time to do anything yet.

Ken
_______________________________________________________________________
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

I still don't

> know if it would work. I've thought about if often enough, but

haven't had

> time to do anything yet.
>
> Ken

Well, I need to get parts for repairing a friend's Fender Twin
anyway. I'll pick up a 6AR8 and find out!

Chub