Wider sweep for Crybaby wah

[MohiZ]

Hi again! I'm sorry if this is a boring topic but I couldn't find what I was looking for by searching.

So I just got a CryBaby wah, but I think its sweep range is too shallow. I know it's not about the circuit, because I was playing with a CryBaby clone inside a Bespeco Weeper wah casing. The difference is that the Bespeco wah pot actually moved from 0 to 120k (the full range of the pot), but the Crybaby's range is only from 0 to around 80 kilo-ohms (the full value being about 110k), limiting the bass portion of the sweep. It sounds MUCH better with the full sweep range available. Unfortunately the Bespeco's mechanism was a piece of ****, and the pot was scratchy and bad. I can't use that. That's why I got the Crybaby.

Does anyone have an idea to increase the range of the Crybaby, mechanically? Are there gears that have less teeth, allowing for the pot to be turned more with the treadle movement? How much effect does a larger wah pot have? Is the wah pot acting like a voltage divider in the circuit? Or is the only thing that matters the resistance between ground and the center lug?

Thanks for reading.

[Dai H.]

something typically done seems to be cutting the rubber bumpers down a bit (and carefully adjusting the footswitch height so the wah isn't accidentally switched off--there may be a degree of personal preference involved here--some might like it relatively more difficult to actuate while others may like it easier)

[GibsonGM]

Jimi took at least 1 of his off, so the story goes.  I have 1 of the front bumpers off, it lets you compress the treadle just that little bit more, enough to get into the highs as much as I want...

[MohiZ]

Oh yeah! That was easier than I thought. I just removed the bumpers (all of them), and now I have access to the full rotation of the pot. However, I now noticed that the pot is actually only 80k. Does a higher value pot facilitate a wider sweep? If so, why? It's not like you get more volume by replacing a volume pot with one of a higher value, for instance. Well, maybe a little but not that much anyway.

[Dai H.]

not sure but the taper definitely seems to matter(having had the experience of using around five different pots). Tweaking the first transistor also helps to get the wah effect in the low freq. end, and 100k rather than 33k for the R paralleled to the inductor sounds "wider" to my ear. Also, forgot to mention the felt thing(bumper?) on the top part of the wah(treadle) glued to the underside of it right above the footswitch (actuator?). Removing (or thinning somehow, replacing with something thinner) can also help free some movement, though of course we're not talking huge amounts here but it can still make a bit of difference. If it's removed entirely however, you might not like the "clank" when the treadle hits the switch actuator so may want to have something.

[MikeH]

You could also change the sweep cap.  I used a 7 position rotary on mine; It's basically the same as the sweep cap select on a 535 wah.

[skiraly017]

Buy a Dearmond wah or volume pedal, gut and insert wah circuit of choice. The Dearmond's have a huge range and the volume pedals can be had pretty cheap.

[Thomas3D]

http://www.wah-wah.co.uk/diy.html
look at the Sweep Range section

Change the sweep by swapping the 0.01µF cap between the emitter of Q2 and the inductor. A smaller value will make the wah sweep more trebly and vice-versa. If you're converting to or from a bass wah, this is the one to change. Try 0.068µF for a bass wah.

as suggested earlier in the thread do the sweep range mod with different sweep capacitors on a rotary switch, this way you have a more versitile wah that you can change on the fly. highly recommend this mod.

[MohiZ]

Thanks, although I've already read about most of those mods. The sweep cap doesn't widen the sweep, and actually I'd like to have a wider sweep accessible with the pedal, instead of just, you know, turning the knob when I want to access different ranges. I removed the bumpers on both sides of the treadle (I don't mind the clang  ) and that actually made enough difference to be able to utilize the full range of the pot, which is great! Just have to set the switch height just right so it doesn't get pushed by accident. It's all about compromises.

I've been tweaking the values of different components for hours and it's starting to sound pretty good now. I came to the conclusion as well that a 100k Q resistor makes it sound very vocal. I had a pot wired instead of the resistor and after setting it just right I measured it and it was almost exactly 100k. I'm still going to try to figure out if I can somehow get an even wider range.. maybe by trying different transistors or sumptin.

[R.G.]

Technology of the wah pedal.

The range depends on how much you can change the apparent capacitance of the resonant circuit. Even then, the frequency changes as the square root of the capacitance change, so you have to have ever-higher changes in capacitance to make the sweep bigger. It's already at the point of diminishing returns, so there are not going to be huge changes.

You have to ditch the inductor/cap wah and go to something like state variable to get around the square-law problem. A state variable can give you full audio sweep.

[MohiZ]

Thanks, R.G.! I've read your article on the technology of the wah pedal, and it was very good. I guess I'll have to look into other types of wah circuits then.

[matt239]

Old thread, but, in case anyone is wondering the same thing; Joe Gagan has made a gear with different teeth..

Also the idea of the DeArmond shell, then experiment with some different wah pots.

At that point, you will have reached the limits of the circuit, as R.G. said.

A Colorsound inductorless style circuit isn't too hard to build.
I think they sound great!

P. S. :  Also, plugging an un-buffered wah into a low impedance input, such as an old school fuzz, can limit the sweep.
Might have a lesser effect with some pedals with a mediocre input impedance..
An output buffer on your wah, solves this.

[Transmogrifox]

Something RG didn't point out in the technology of the wah article is that the loop gain changes the sweep range.

While it's true that the square law pushes you up against diminishing returns there is a little bit you can get out of it.

For example, I think the GCB-95 is too wide of a sweep and I prefer the Vox V847 better.  The difference?  Emitter resistor in the Vox is 510 ohms (or something like that) and the GCB-95 is 390 ohms.  GCB-95 sweeps wider. 

My GCB-95 also has a 100k pot and the mechanical assembly sweeps the full range.  What model do you have?

The pot value WILL make some difference in the sweep range although the amount is more subtle than the emitter resistor.

The difference is, a simulation with the Vox can sweep the lower range to about 550 Hz and the GCB-95 can sweep the lower range down to about 420 Hz, and a modified circuit can get down to 350 Hz.

Once you push the limits much further than that then you come up against circuit stability problems, but you CAN milk more range out of a wah if you want.

My personal experience is increasing range decreases the wah usability.  I prefer the shorter range of the Vox all shifted lower so most of the travel is focused on the 500 Hz to 1 kHz range where the vocal "wah" comes out.  If you want to increase control over where "wah" breaks, then limit the range.  If you want more of a synth filter sweep, increase the range.  If that is not enough then do as RG suggested and use a state variable filter or something.

If the DeArmond was a good sound, then replace the Crybaby pot with > 100k and mod the circuit to match DeArmond.  I think this pretty much tells you the sound OP wanted is attainable.  This mentioned for posterity...probably lots of others read even old posts

[matt239]

Good points. Thank you. 😊