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DIY Stompboxes => Building your own stompbox => Topic started by: Sauerkret on November 11, 2009, 07:38:44 AM

Title: parametric EQ and a wah
Post by: Sauerkret on November 11, 2009, 07:38:44 AM
This is a schematic of a parametric EQ.
I would like to us it as a bandpass filter (wah)

The filtering section is basically a Craig Anderton super tone control wah.
(http://img201.imageshack.us/img201/7786/andertonsupertonecontrozr1.gif)
Would I need to modify this circuit? Could I remove the mid control (green box) because I'll use the dual pot to sweep through the mids. And how would I wire this up?

(http://i236.photobucket.com/albums/ff26/sauerkret/Untitled-2.jpg)

Kind regards, Eric
Title: Re: parametric EQ and a wah
Post by: Sauerkret on November 12, 2009, 03:41:05 AM
Bump
Title: Re: parametric EQ and a wah
Post by: fuzzo on November 12, 2009, 08:16:24 AM
The mid control seems to be the boost/cut control. But you can keep just the bandpass filter made by the three AOPs and sending your input signal into the first. The dunlop Q zone ( is made in the same way) . Look at its schematic , that's very close.

Title: Re: parametric EQ and a wah
Post by: Ben N on November 12, 2009, 12:00:59 PM
You could make the mid pot a trimmer.
Title: Re: parametric EQ and a wah
Post by: Sauerkret on November 13, 2009, 04:11:00 AM
another thing that i am curiouse about is why there is a Dual  potentiometer instead of a regular single pot.
is this crucial to the filtering? and why would that be so?

thanks, Eric.
Title: Re: parametric EQ and a wah
Post by: Shepherd on November 13, 2009, 03:50:44 PM
Anderton addresses the idea of turning the Super Tone Control into a Wah pedal in his book.  If you don't own the book already, it might be worth picking up.  In any event you need to find a treadle that will accommodate a dual ganged potentiometer.
Title: Re: parametric EQ and a wah
Post by: puretube on November 13, 2009, 06:47:05 PM
Quote from: Sauerkret on November 13, 2009, 04:11:00 AM
another thing that i am curiouse about is why there is a Dual  potentiometer instead of a regular single pot.
is this crucial to the filtering? and why would that be so?

thanks, Eric.


State Variable Filter*: no need for dual pot - you can use dual-vactrol or 2 OTAs, too...
(or 2 PWM-ed CMOS switches, see "MXR")




*search...
Title: Re: parametric EQ and a wah
Post by: fuzzo on November 13, 2009, 07:05:24 PM
Thanks for the specific works that I didn't know.

with that word google gave me a lot of things ;D
Title: Re: parametric EQ and a wah
Post by: puretube on November 13, 2009, 07:22:03 PM
Quote from: fuzzo on November 13, 2009, 07:05:24 PM
Thanks for the specific works that I didn't know.

with that word google gave me a lot of things ;D

Yep: the most interesting thing in the first schemo of the >1.5 million google-returns is: Rf1=Rf2 ...  :icon_wink: