Wiardgroup

I wanted to post a note about the "Lowpass Gate" and its usage
throughout electronic music, for the purpose of clarifying why some of
us have obsessed about them....

From the 200 Series Brochures, circa 1970s:

"The Model 292[Quad Voltage-Controlled Lopass Gate], with the
capability of simulating the spectral and amplitude changes that
accompany a receding sound source, is one of several Electric Music
Box modules that can deal with spatial localization and movement."

There were three opreation modes for these devices - filter, vca and
dual.  Obviously, when in dual mode, the lopass gate operates as both
- a filter(6db/oct) and a VCA.

This dual mode is the sound of Mort Subotnick's electronic
realizations of the 70's.  It has a characteristically "woody" chirp
to its transient character.  It is this mode that most of us who used
the old Buchlas miss, hence the quest for "LowPass Gates".

The issue with the recent versions of this circuit is that most of the
versions of the the LP gate is that they are too slow.  When hit with
a short transient, they tend to ring excessively, making the "uber
marimba" patch made famous by Subotnick all but impossible without
slapping a VCA after the gate to shorten the sound.  The old Buchla
had only a 1v ptp audio signals, so the vactrol didn't have as far to
go to open all the way up, compared to the 10v ptp audio signals found
on Wiard and many other systems, so it was very quick.  As a matter of
fact, even the new 200e has very slow lopass gates, needing a second
gate in VCA mode to shorten the ring.  This is not typical of the 70's
200 series 292 gates.

Then in comes the Borg2, and we have a perfect 10v ptp lopass gate -
even better than the original (which are 1v ptp and had a "dual
linear" - as opposed to logarithmic cv curve).  

I also love to use the original Borg Filter for multichannel panning
with the JAG, because it rolls off the distant channels (just like the
227 quad locator of the Buchla 200 system), while opening up to full
bandwidth where the sound is nearer.

So, that's the lowdown on this LowPass Gate business....

gary