[sdiy] Buchla Lowpass Gate Switch

[Peter Grenader]

Did you use an on-off-on switch?  This is the type that rests in the center
so that no connection is made to either pole.  This is all you need to do.
With neither of those connections made (or with the switch removed
altogether) you're in fact in combination mode. If you don't use a switch
with a center position however, you can't get there.

A little more about Mark's LPG:

He chose the rev C  lowpass gate for this rendering.  It sounds terrific,
and while all of the Buchla Lowpass gates leak a little, the rev C does so a
bit more (about 3mv with the vactrol fully closed).   This is not a fault
with the circuit outside of the fact it was designed to pass  line level
amplitudes.  When you get into the modern day uber-levels of 5 plus volts
they tend to bleed a bit. I have a modification that improves this (gets it
down to about .3  mv while boosting the output a dB or so)  but it requires
the rev B LPG circuit.

That being said, its not really a problem unless you're gating signals with
high harmonic content (like an FM'd signal) in dead silence

hope this helps,

- P

Peng wrote:

Hi,
 
 I recently finished the Lopass Gate using Mark Verbos pcb. Works good. I
put in a 2 position toggle to switch between lowpass/gate. I'd like to have
a "both" position but can't figure out how to do it ( experiencing a brain
freeze or something!). I have some SPDT center off and DPDT center off.
  I had an idea to replace the -7.5V that goes to 1M resistor on pcb with
+7.5V, then put  
-7.5V to middle lug of toggle. That way, if it's in the center (off)
position, I'd get the both response ? Just a guess.
  I searched this out in the archives first (of course) but didn't find
anything, though there are references made. As a side note: On the search
page of SDIY I typed in " Buchla Gate" - no results. Next tried "Buchla" -
many results. One read "Buchla 292 Lowpass Gate" - this should have come up
on first search. Next "Buchla Lowpass" - nothing. Lastly "Buchla 292" - got
results. Seems you need to get the words in order, or just try to get the
first word. Maybe I'm missing something ? If not, then it's a good thing to
keep in mind when searching ( or posting for that matter ).
 
Thanks,
P.


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