fixed-wha (dunlop Q zone)

[fuzzo]

Hi guys,

I want to build a pedal similar to the dunlop Q zone in a dead boss enclosure (DS2). So I need a wha shematic without inductor (useless for this little project). Actually, the wha circuit must have two controls (wha and Q or resonnance). So I find two schématics :

classic morley wha

http://www.morleypedals.com/pwa-iies.pdf

but it has just one control (the lrd can be change to a Pot). How add a Q control ?

Simple VCF

http://www.geocities.com/tpe123/folkurban/fuzz/simplevcf.gif

But I've a doubt, this filter can produce a Wha sound ? The design is very close to the morley but I'm not sure.

What schematic I can use ?

-How add a Q control in the morley's design ? put a 500K pot instead of 470K R in the feedback loop (It'll change the gain of AOP) ?
-I can add the resonnance pot in the morley ?


thanks

[ZiggyZipgun]

I used to have a Dunlop Q-Zone; great pedal, handy to have, though really only good for one song, or at the most, two.

A quick visit to DiscoFreq's site turned up this:

-->Keep in mind this was drawn from the looking at the pedal, and has not been built or tested, but I'm sure this would be a better starting point for making something along these lines.

[Thomas3D]

http://www.aronnelson.com/gallery/main.php/v/Cab42s-layouts/cil_wah.gif.html


this may be another way to go, has note at the bottom of layout for a q mod...

[fuzzo]

I did the colorsound inductorless but the sound wasn't like a want , beside there's a kind of volume lost.

Yeah , I know the Q zone schematic but I prefere doing something more personal than copy it. Anyway, this wha won't be alone, I'll add another circuit with it.

I did  research fonction yesterday evening, and a lot people have did the Morley, so I think it's a good start but the VCF seems to be cool too, but I don't know if it can produce a whawha sound or it's just a "synth filter". (It's very close to the Morley design (expect the Freq pot.))

[fuzzo]

Any ideas about the schématics posted in the first post 

[earthtonesaudio]

R1 in the Morley could be used like a "resonance" pot, but it will also increase the gain, and raise the frequency range.  There are some other possible places for a "resonance" like control, but with some limitations. 

The VCF should produce the same "type" of sound as both the Morley and the Colorsound inductorless wah.  These are all modified "twin T" circuits, which produce a slightly different sound than the "state variable" filter type used in the Q-Zone.  Some people think the "twin T" filters sound more synth-like, whatever that means.  Read this: http://www.geofex.com/Article_Folders/EQs/paramet.htm for more info on the twin T, and other filter types.

Bottom line, if you want the sound of the Q-Zone, you should use the same filter topology.  I believe state-variable filters are used in the Mutron and its clones, and the MXR envelope filter.

[fuzzo]

Ok thanks for your explanation.

How works the CV ? it's the controlled voltage I guess but we can plug any controller ? 

[earthtonesaudio]

The voltage in produces a small current through the 100k resistor, which turns the LED on slightly, which makes its resistance lower.  Change the resistance: change the filter frequency.

[fuzzo]

Ok thanks, I'll think I'll do this one. But I can connect a LRD or an expression pedal into the CV ?