[sdiy] Voltage controlled version of Moog Parametric EQ circuit?

[JH.]

Hi,

while asking around about filters to be included into my proposed "famous 
fixed filters" PCB,
another idea came up, which has caused a lot of resonance so far:
People want a Moog(TM) parametric EQ.
(Moog is the registered trademark of Moog Music. The Moog Parametric EQ was 
based on a - now expired - patent of Dr. Moog and Norlin. AFAIK)

But just cloning that circuit woud be boring, and would require very special 
potentiometers.

So why not design something that is even better than the original, while 
still preserving the original's behaviour?
This leads to the voltage controlled M-Para-EQ.

The PCB would contain the electronics for the EQ, including the voltage 
controlled frequency sweep.
Everybody has the choice to build it as a voltage controlled device, or just 
like a "simple" Moog-style parametric EQ.

Options for Frequency control:

(F1) Voltage controlled sweep, either of individual bands, and/or of all 
bands with one CV. Manaul control of frequencies with ordinary linear 
potentiometer.
(F2) Manual frequency setting with dual 100k reverse audio taper (-log) 
potentiometers
(F3) Manual frequency setting with dual 100k audio taper (log) 
potentiometers.EMS-HiFli style front panel labeling that allows for high 
frequencies to be on the ccw end of pot.
(F4) 23-position rotary switch (as used in High End Audio Amps) for precise 
setting and recall of frequency, but without continuous sweep.
(F5) 23-position rotary switch for precice manual frequency setting, plus 
voltage control for continuous sweep.

Options for Bandwidth control:

(B1) 6-position rotary switch. (You can use a 23-position as well, but that 
would be overkill, IMO.)
(B2) Build your own special pot from a dual 50k log and a single 500R lin 
pot, and some adventurous transplantation.

Options for Cut/Boost control:

(G1) Potentiometer (no special type required)
(G2) Rotary switch (11-position or 23-position)

Any combinations of F, B and G options are possible, by just connecting 
different front panel parts to the same PCB.

Interested?

JH.