[sdiy] Low Pass Gate passing DC - forgedabouydit

[mark verbos]

The Buchla 230 envelope follower is NOT a vactrol circuit. It is more or 
less just a full wave rectifier. There are extra controls to make the 
decay time and the pulse output section.

check it out here. http://home.swipnet.se/cfmd/synths/companies/buchla/

mark

Peter Grenader wrote:

>Hark, the possiblity of yet another string on this already  over-cooked
>subject (me being the primary chef involved):
>
>But i thought you guys would like to know that if you try and gate a contant
>DC level through a Buchla low pass gate circuit, it just cocks it's ear at
>you like a dog and does nothing.
>
>I was hoping to replicate (foolish me) that famous (in my world anyway) Mort
>Subotnick percussive slap used on Until Spring and Sky of CS.  He did it
>using a control track which was fed through a Buchla Envelope Follower
>(which i believe is vactrol based) which was not only trigger the envelope,
>but creating the frequency transcient as well.  The EF was set  to a very
>fast decay which was going through a voltage processor and processed to
>barely make a tiny upward  frequency spike to the sounding oscillator right
>at the beginning of the attack.
>
>No use arguing how he did it, I dropped him a note a couple of days ago and
>this is straight from the butterfly's mouth, so to speak.
>
>Why i  suspect the B Env Follower to be vactrol based is if you listen to
>those trancients he created, they are very breathy.  I assumed this was due
>to a vactrol's slow response awakening to the control track bleep. It
>created a timing thing that gave you barely a hint of the transcient.
>
>So, since I don't have a Buchla Envelope follower, I figured I could get the
>same result if I used a trigger as the control signal in my Low Pass Gate
>clones,  gating a pot-variable constant DC level.  By gating a constant
>level, I figured I'd be able to adjust it until I would hit the timbral
>sweet spot
>
>But ooooooh-nooooooo, this circuit deosn't respond to contant DC levels at
>it's input (makes sense since-in the intrument for which is was designed
>there was no way of getting that DC to the gate signal input anyway).
>
>If anyone knows if the Buchla Ebnvelope Follwer used a vactrol, I'd be much
>oblidged.
>
>let me know and thanks,
>
>Peter
>
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