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

[Carsten Tönsmann]

Hi Juergen,

this sounds very interesting and I would like to build this thing (but only 
if there are no rare electronic parts in use :-)). I made some good 
experiences with the quite simple Formant paramatric equalizer / resonance 
filter module and I also thought about a voltage control.

Looking forward to it!

- Carsten

----- Original Message ----- 
From: "JH." <jhaible at debitel.net>
To: <synth-diy at dropmix.xs4all.nl>; "analog heaven" <analogue at hyperreal.org>; 
"MOTM List" <motm at yahoogroups.com>
Sent: Friday, November 30, 2007 8:20 AM
Subject: [sdiy] Voltage controlled version of Moog Parametric EQ circuit?


> 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.
>
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