[sdiy] Vactrol'ed Moog Parametric - or stepped controls?

[JH.]

>A very good idea, but how well matched are vactrols?  Would there need
>to be a lot of calibration/trimming required?

That's a good question.

Needs a lot more simulations to find out.

My gut feeling is that there wouldn't be much trimming needed (unless you 
need precise labelling of the front panel controls), but we'd need at least 
3 different types of vactrols. It's certainly possible, but needs a lot of 
design work.

An different route to go would be going for ultimate precision, and forget 
about voltage control:
Using rotary switches instead of potentiometers:

You'd get quite a good frequency resolution, using 23-position rotary 
switches that are favored by High End Stereo Amp builders.
For Bandwidth, a 11-position switch is certainly enough. And another 
11-position switch for cut/boost.
The good thing about *this* is that you can even mix the switch and 
potentiometer approach:
Use potentiometers for Frequency and/or Cut/Boost, but a switch for 
bandwidth, if continuous sweeping is important for you.
Or use switches everywhere if precise recall of settings is important to 
you.
Gladly, the one control that is the most tricky to implement with 
potentiometers (the bandwidth), will suffer the least from a stepped 
control, IMO.

JH.