[sdiy] Buchla Lowpass Gate Switch

[Peter Grenader]

Mark-

I used a straight double on-off-on on my rev B's and I've got combo in the
center. I'll be happy to post an mp3 to illustrate this!

Have a look as the schematic- the top half of the switch puts 15K across the
output of the second vactrol element, killing the filter.  The Rev C does
the same thing, but does so with only 10k. The bottom half of the rev B
switch increases the cap value, (.0047), just as C does. The additional
third switch element in the rev C adds 15k to the input signal's amplifier,
increasing it's gain.  Granted, the rev B doesn't do this, but this addition
does not effect the mode switching, it just ups to output of amplify-only
operation. This is why I didn't see that an on-on-on was required and as it
turns out, it seems to work fine without one.

- P



> it actually doesn't save anything because the switch the rev B used is a
> On-On-On switch, which is even more rare and pricey than the 3PDT one!
> The reason i modded the rev C was because of price. I wanted a cheap and
> simple solution. Also the wiring is easier than using multiple pole
> switches. Fewer wires, smaller switches that can be closer together,
> easier to get, cost less. Seems like an obvious choice to me, but I
> guess not for everyone...
> 
> mark