[sdiy] vactrol panning (across 4 outputs?)

[Karl Ekdahl]

Well you have a totally different issue if you're working with two CVs (x/y) then if you're just using one. With two CVs it's as simple as using a 2-quadrant multiplier to get the total cv (cv = x * y) and then another 2-quadrant multiplier for the actual sound (out = in * cv). If you only have one CV you need to make an interpolating scanner which is another story.

Karl

--- Den sön 2011-01-16 skrev alfred.pear at gmail.com <alfred.pear at gmail.com>:

> Från: alfred.pear at gmail.com <alfred.pear at gmail.com>
> Ämne: Re: [sdiy] vactrol panning (across 4 outputs?)
> Till: "Karl Ekdahl" <elektrodwarf at yahoo.se>
> Kopia: synth-diy at dropmix.xs4all.nl
> Datum: söndag 16 januari 2011 23:44
> Hey Karl-
> 
> Nice box - a little bit out of my price range, especially
> since I need two.
> 
> I was actually using a joystick with an LED attached under
> the
> chassis, that would shine onto partitioned photocells - but
> alas, no
> CV, which is really what would be ideal.
> 
> Can you say anything about scaling the CV across several
> VCAs or is
> that top secret?
> 
> -AP
> 
> On Sun, Jan 16, 2011 at 10:45 AM, Karl Ekdahl <elektrodwarf at yahoo.se>
> wrote:
> > I realize that this might not at all be interesting
> and it *is* shameless self-promotion, but nevertheless...
> >
> > http://www.knasmusic.com/products/quadmassager/quadmassager.php
> >
> > Karl
> >
> > --- Den sön 2011-01-16 skrev alfred.pear at gmail.com
> <alfred.pear at gmail.com>:
> >
> >> Från: alfred.pear at gmail.com
> <alfred.pear at gmail.com>
> >> Ämne: Re: [sdiy] vactrol panning (across 4
> outputs?)
> >> Till: "Tom Wiltshire" <tom at electricdruid.net>
> >> Kopia: synth-diy at dropmix.xs4all.nl
> >> Datum: söndag 16 januari 2011 15:08
> >> Tom -
> >>
> >> I was under the impression that a scanner shifted
> from
> >> inputs, rather
> >> than sent a single input to multiple outputs - so
> I'm
> >> apologize for my
> >> lack of clarity...
> >>
> >> The goal is a circuit that will take one inputs
> and "pan"
> >> it across
> >> four outputs, one by one, with a single voltage,
> preferably
> >> in a
> >> compact design similar to the simple panning
> implementation
> >> (sorry
> >> Aaron).....
> >>
> >> I was hoping there might be a way to put a current
> mirror
> >> inside the
> >> current mirror...but I don't really know..
> >>
> >> -M
> >>
> >>
> >> On Sun, Jan 16, 2011 at 8:24 AM, Tom Wiltshire
> <tom at electricdruid.net>
> >> wrote:
> >> > Sorry Alfred, I'm not quite clear what you're
> trying
> >> to do.
> >> >
> >> > Do you want the two extra channels to be
> copies of the
> >> existing two channels, or are you aiming to build
> a
> >> 'quadraphonic' version of the circuit?
> >> > Or do you have a 'four channel scanner'
> circuit in
> >> mind, where the output can be 'panned' from output
> 1 to
> >> output 2 to output 3 to output 4 under the control
> of a CV?
> >> >
> >> > The circuit itself looks to be a pair of
> "optical"
> >> VCAs, as used in many famous compressor designs
> (very simple
> >> audio path, so low noise, and the slow LDR
> response gives a
> >> natural sound). The vactrol's LEDs are driven with
> a current
> >> mirror, which provides the panning action (one
> goes up
> >> whilst the other goes down).
> >> >
> >> > Thanks,
> >> > Tom
> >> >
> >> >
> >> > On 16 Jan 2011, at 05:00, alfred.pear at gmail.com
> >> wrote:
> >> >
> >> >> hi synthesists -
> >> >>
> >> >> i'm sure many of you are familiar with
> this very
> >> elegant two-channel
> >> >> panning circuit, using two vactrols
> (based on a
> >> buchla design,
> >> >> apparently):
> >> >> http://www.simple-answer.com/vac-panner.jpg
> >> >>
> >> >> i feel like there must be a way to nest
> and scale
> >> several transistors
> >> >> in there to make this circuit response
> across four
> >> channels of
> >> >> output....but i'm not a very skilled
> designer..
> >> >>
> >> >> any suggestions?
> >> >>
> >> >> sincerely,
> >> >> a. p.
> >> >>
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