PLAN B analog blog

The trimpot of the Model 11 offsets the faceplate frequency pot  and
provides a means of 'centering'  the freq's pot effect on the filter's
center frequency.  If you notice the Freq pot is heavy on the upper
end of the pot's travel then you should consider doing this:

It's best to do this while the VCF has some resonance to it so that you can distinctly hear all the partials.  

To adjust:

Monitor the 12dB output and turn the freq pot fully CCW (all the way
closed)

Using a pot tweeker, turn the M11's trimpot fully CW (you'll hear it
open), and then back it down.  You'll notice the frequency start to
close up anf then it'll reach sort of an elbow where it closes down
rather quickly.  In short, this trimpot does not have liner response.
Adjust the trimpot so it's right at the elbow where the filter
frequency is fully closed.  

The trimpot is somewhat sensitive.  Just take your time until you feel
the you've centered the faceplate's freq pot's effect on the center
frequency of the filter. This trimpot will not cause any damage to the
circuit whether it's in adjustment or not.

Make sure you've got some resonance dialed in or you will not hear the
effect of the faceplate pot movement on the input signal's lower partials.

This is easy to do, don't sweat it at all.

- P