Yes... what Peter said.

Regards,
Kevin

--- In Doepfer_a100@yahoogroups.com , "(i think you can figure that
out)" <petergrenader@h...> wrote:

> This post might be a tad long. I am responding to two
> comments regarding vactrols:
>
> A) Has Dieter ever fooled around with vactrols
>
> Answer: TRUE (yes)
>
> B) Vactrols are sonically unexciting.
>
> Answer: FALSE (no!!!!!)
>
> I come from a point of confidence on both these as I have
> discussed this with Dieter and as well I designed the circuit
> modifications for the Cynthia Buchla Low Pass Gate module in
> order to improve the response with non-Buchla voltage
> configurations. I also have about a billion hours clocked on
> Buchla synthesizers.
>
> Item A explained:
>
> Yes, the Doepfer folks have looked into using vactrols. Dieter
> has even experimented with making his own. This in itself ain't
> all that hard, as a vactrol is nothing but an led and a photo
> resistor positioned so the light path is pointing to the business
> end of the photo resistor, and the whole mess potted into a
> plastic enclosure so that ambient light does not effect the
> resistor. Usually this results in this 'thing' that has two led

leads

> sticking out of one end, and the resistor leads out the other.
>
> How a vactrol works is the brighter the light, the lower the
> resistance of the photo resistor. There are few different types,
> each having it's pwn characteristics: delcay time, on/off
> resistance values, dual or single (some are confiugured as
> pre-wired voltage dividers consisting of two photo sensitive
> resistors in series).
>
> So there's that.
>
> B explained:
>
> OK, I understand that this comment was an opinion and therefor,
> completely acceptable. But given that everyone is due their own
> opinion, here is mine:
>
> Vactrols are friggin' wonderful in synthesis applications.
>
> Will they give you the snap response of a non-vactrol circuit
> equivelent NO. Are they the best thing to have in a VCA which
> (most engineers wil tell you) have to be fast to be good NO.
>
> In analogy: Is the Wasp filter a good design NO. It's a horrbile
> design by engineering standards, it's a mistake - but that
> mistake sounds good.
>
> Such is the case with Vacs as well, although they were
> intentionally introduced by Don for the purpose of noise

isolation.

> Remember, the Buchla signal level is just about line level. In
> order for it to be heard, it has to be turned up like made and this
> is where noise can cause you grief.
>
> Someone also mentioned they were in a Buch to keep the
> control voltages isolated form the singal path, this is 99.9% true
> in all cases accept (to my knowledge) the envelope detector in
> which the control voltage generated from the external signal is
> not isolated from the signal path electircally.
>
> Remember, not only is the Buchla signals and controls
> separated by two distinct patch cord systems, they run off of
> completely different supply systems and different voltages in
> some cases. While the signal paths is fed with 15 volts, some
> of the control modules are powered off of 24.
>
> Let take the 292 Low Pass gate as an example. It is, by nature
> and due to the vactrols, slower than shit. Most design engineers
> would tell you that this makes for a very bad VCA design which
> are supposed to be fast to be efficient. Due to the vactrol's
> naturally slow decay time (35 MS), and the fact that the main
> mode of operation of a 292 is a low pass filter, vactrols afford a
> unique ringing of the low frequency spectra of a signal which
> provides the percussive phrases with a lot of life. I will post a
> link by day's end of a comparison of the same signal gated by a
> standard VCA and by a lowpass gate - you'll know what I am
> talking about in a second.
>
> Why is the decay so long in a vactrol It's the light. Turn an

led

> on. Watch it snap to attention. No turn it off. Ah-HA - it fades

out

> even if the signal going into it cuts instantly.
>
> So no, in my opinion, the while use of vactrols in analog
> synthesizers provides a marketably different result than
> functionally identical circuits not using them, they are no worse,
> just different and in some cases, that makes for a pleasent
> results.
>
> VIVA LA DIFFERENCE!
>
> Look for a posting with a link to sonic exmaples of the 292 in
> action soon.
>
> best,
>
> Peter
>
>
>
>
>
>
> --- In Doepfer_a100@yahoogroups.com , "klamb000"
> <lamb@c...> wrote:
> > Actually, I think it was said that the Buchla designs weren't as
> > sonically pleasing as other designs.
> >
> > And I also wonder if any vactrol modules are planned for next
> year.
> >
> > Regards,
> > Kevin
> >
> > --- In Doepfer_a100@yahoogroups.com , "ethanzer0"
> <ethanzer0@y...>
> > wrote:
> > > A while back there was some discussion
> > > on vactrol based modules. I believe
> > > the thoughts were that vactrols in the
> > > audio path are not that sonically exciting.
> > > Looking at buchla schematics I find that
> > > vactrols are used quite often to isolate
> > > the control path from the audio path
> > > (optoisolator ) I understand the ultra-smooth
> > > response of vactrols make a modules response
> > > to CV something special. I wonder if the
> > > design folks over at doepfer have considered
> > > this
> > >
> > > Ethan