DIY Fixed Wah Effect?

[overdrive]

Outside of the timeless duct tape method of setting a wah pedal to a fixed position, is it feasible to simply put a wah PCB & necessary hardware into an enclosure using the potentiometer to manually set the sweep? As most standard wah pedals generally don't have them, is a level (volume) control a critical addition to the circuit?

[Mark Hammer]

Yes, and a number of manufacturers do just that.
Just for interest though, give the Small Bear "Wild Mouse" a looksee. Tremulous Bear

[overdrive]

Cool. How critical is a level control & can that be accomplished by simply adding a JFET or MOSFET booster circuit to the overall layout?

[Mark Hammer]

You can pretty much add a volume control to anything, since you'll always want a terminating resistance on the output. I haven't looked closely, but I suspect there is enough information in the Wild Mouse document to show how and where to do it. If the circuit is designed for unison output in bypass or effect mode, though, you'll have to mod it to make effective use of a volume control/preset.

[overdrive]

Most of the DIY schematics in reference to this sort of project seem to utilize an IC & a small transformer serving as the inductor. To me, the traditional Fasel/Halo inductor sounds more organic & I would like to source a RTS PCB with that capability or worst case scenario, modify an existing wah circuit PCB. Not particularly interested in creating an auto-wah or having that option.

[surfsup]

overdrive, have you put a fixed wah together yet? I am wanting to do the same thing and just stumbled on your post. I would like to also use an inductor to get a true sound.

[Gtr_tech]

Its super easy to do kids. Just buy a used crybaby for a few bucks and take the board/jacks/etc out of it and rehouse it in your choice of enclosures. The only thing you'll have to buy a 100k pot and mount that in your new enclosure to take the place of the gear driven one. Taper don't matter...you can use linear with good results. Actually Linear may actually work *better* for a fixed wah filter. I think thats what I used in the one I built 20 years ago....

[overdrive]

overdrive, have you put a fixed wah together yet? I am wanting to do the same thing and just stumbled on your post. I would like to also use an inductor to get a true sound.

Completed it a few months ago. I built the circuit on a perfboard with a halo inductor from Small Bear & a 1590 Hammond enclosure.

[pinkjimiphoton]

ever try the phunqgnosis pedal by tim escobedo? it does the fixed wah thing pretty good, and you have the option of a pretty good auto wah with the flick of a switch.

[Brad1]

Just to be kind of obstinate..."fixed wah" is kind of an oxymoron, isn't it? If it's "fixed", it's simply a filter. It doesn't "wah" without movement.

But, I digress. The term came from people playing through cocked wah pedals in a fixed position. I just always thought the term was kind of amusing...but musicians have an endearing habit of playing around with terminology, mixing things up (vibrato/tremolo) and calling things humorous names.

Having said that, this got me to thinking about any possible advantages of having a "fixed wah" pedal with a rotary switch (or programmable switching) for, say, 10 different settings, with a pot to fine tune them a bit? So, instead of trying to replicate the settings of the full sweep of the wah pot that just got bumped, you could get a lot closer to your target tone on, say, setting #7, with a bit of tweaking around it? if another tune demanded, say, a deeper sound not as bright, maybe quickly switching to setting #4 or #5 would work?

May be kind of cool to incorporate a "Mix" control, also, to output normal signal with nasal tone blended in, more filtered tone with normal blended in, or anything between or at the extreme?

Does anyone already make something like that (other than maybe just a programmable EQ or something)?

Brad1

[R.G.]

A wah pedal is a low-Q (that is, wide resonance) bandpass filter with some low pass mixed in.

You can do a really creditable job of making a resonant filter without an inductor. Since it is not swept, the "vocal quality" is not at issue. This can be done one of several ways that actually have been used for wahs: multiple-feedback and Twin-T filters come to mind. It can also be done other ways, including the supremely flexible and adaptable state variable filter, which is what is inside the Mutron envelope filter. There are many ways.

The state variable in particular lends itself to presets for center frequency, Q/resonance, and gain; it also gives you outputs of highpass, lowpass, bandpass, and notch filters all at the same time, as well as the controls not interacting. An SV built from a single LM13700 gives you voltage control of frequency through at least a 100:1 range, much more than you'd ever need for a filter like this. The trick would be limiting the range to what you want.

Multiple feedback filters use one opamp and one transistor per filter; examples include the Seamoon Funk Machine and the Dr. Q.

Twin Tee filters need one or two transistors per filter.

The entire design issue with this is to define what frequencies, how sharp the resonance, and so on.