Archive of the former Yahoo!Groups mailing list: MOTM

Has anybody bothered to tweak their 410 so that the filter
frequencies are all the same when the FREQ pots are all set to the
same value?

I've noticed that if I pump a 1000 Hz sine wave into my 410s and then
adjust the FREQ knobs so that each filter output is at its loudest,
the FREQ knob settings vary between 3.0 and 5.0. That's quite a range
and makes it rather difficult to correlate a FREQ knob setting to a
Hz value when trying to dial up formants for speech synthesis.

Since the filter resistors are inside the Vactrol they can't be
changed. Changing C6-C8 is unlikely a solution since caps are not
available in a wide variety of values with 1% tolerances. It looks
like the best solution is to tweak the Vactrol LED current through
R54, R57, R60.

I was wondering if anybody has already done this on their 410, or has
another solution. Or am I just being a nutcase?