New Wiard Module: Borg "Assimilator" Filters

[Harry Bissell]

Its really SCARY when you consult in your sleep...

I once asked my (former) employer if they wanted me to do a consultation with
a fellow (but recently deceased) engineer...

That night... we met. I didn't see his face, just the back of his head sitting
at his desk...
He said "If you want to limit the (fault) current just put a Fvcking RESISTOR
in series
and you can make the current any fvcking thing you want...."

POP!  I woke up.  Went in late the next day and explained I needed the extra
sleep because of the meeting... and delivered the results. It worked of course
!!!

Then I asked them (employer)... "Now WHERE do we send his check to ???

H^)  harry (7 of 10)

Grant Richter wrote:

> Hi All,
>
> I might as well kick off the flood of new products
> with the announcement of the Borg (Buchla-Korg) "Assimilator" filter
> module.
> This is the Vactrol design of the Buchla 292 low-pass gate
> with pannable mode response, regeneration and exponential
> control voltage response. It has low, band and high pass response
> continuously pannable in each section, with resonance up
> to self oscillation available through out the entire pan.
>
> The design came about because I had a dream where
> Don Buchla was explaining to me at a party that the
> 292 WAS a Korg MS-20 filter (That is a Sallen-Key).
>
> The Vactrols also have slew rate limited control voltage
> response that gives everything a very acoustic tone
> character and that HUGE Buchla 200 sound.
> I have prototyped 9 different filter designs so far using
> Vactrols and have built state variables, four pole low
> and high pass, Sallen-Keys and comb filters.
>
> I have also built VCOs and VCAs with them,
> but the VCOs don't calibrate too well and the
> VCAs are "soft" sounding. But the filters are bitchin.
>
> There are three features that are nice with the Vactrols.
>
> 1. The control path is optically isolated from the audio path.
> That means it is impossible to get control voltage feed through.
>
> 2. The control path is slew rate limited. The Vactrols will
> slew about three decades in five milliseconds. This produces
> a noticeable, but fortunately pleasing, artifact in the processed sound.
> It rounds the envelope attacks and gives an acoustic character
> to notes, while still percussive, their more marimba like than metalophone.
>
> 3. The LDR is just a resistor and so does not contribute any
> additional noise. Built with discrete FETs and the LM837
> op-amp the designs are quiet enough to use in line
> with a guitar or microphone. It has become apparent to
> me that fewer parts = less noise and I have been concentrating
> on designs that have the fewest possible number of parts in
> the audio path.
>
> Grant Richter
> http://www.wiard.com