[sdiy] vactrol transfer function

[megaohm]

VTL5C3 is the most commonly used. Probably attributable to all the old
Buchla schematics out there.
  To find out which vactrol type is best for any given application you
will need to buy a couple of each and experiment. I find the data
sheet to be almost useless in this regard.

p.


On Fri, Dec 31, 2010 at 3:44 PM, David G. Dixon
<dixon at interchange.ubc.ca> wrote:
>> I haven't analyzed it closely, but I don't think that a low pass would
>> quite get you there. With many Vactrols, the turn-on time is shorter than
>> the turn-off time. Maybe a slew with different rise and fall time
>> constants?
>
> Yes, I had a look at the Perkin Elmer vactrol application sheet (VT500)
> which Danjel van Tijn kindly sent me, and it's fairly obvious what the
> "special character" of the vactrol is.  I think that a slew circuit with a
> couple of diodes and different resistors would do the job nicely.
>
> Here are the stated response times (on-time to 63% of final R_on, or
> off-time to 100k) for a collection of common vactrols:
>
>                on-time off-time
> VTL5C1  2.5 ms   35 ms
> VTL5C2  3.5 ms  500 ms
> VTL5C3  2.5 ms   35 ms
> VTL5C4  6.0 ms  1.5 s
>
> Based on this, am I correct in assuming that the VTL5C2 is the most useful
> for synth purposes?  Off-times for VTL5C1 and VTL5C3 seem kinda short, and
> the off-time for VTL5C4 seems kinda long.
>
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