[Wah] How to make the sweep range longer?

[minimal]

My wah pedal is a diy based on a tonepad wah project(http://www.tonepad.com/project.asp?id=29). I've already added a sweep range mod but simply moving the sweep range doesn't satisfy me. I once owned a Dunlop JH-1 and it had a pretty long sweep. The one i own now is more like a GCB-95. In what way can I make it much longer?

[zjokka]

A lot i think, depends on getting he pot set right. So that it moves in the right region of the taper, because a wah never uses the complete taper but rather the middle part. Tricky but rewarding job.

What kind of wah pot are you using? Maybe a 200K pot would help..

zj

[minimal]

I'm using a 100k linear pot.

[jonathan perez]

what do you mean by "longer?" do you mean that you want the range to go lower? what mods did you do? what are the values of your resistors, transistors, and capacitors?

[minimal]

I have sweep caps ranging from 0.01uF to 0.1uF. The rest is just like in the project from the link. The thing is that when I switch to a bigger sweep cap the tone with the heel up is very dull. And with a smaller sweep cap the tone in the heel down position is not muddy enough. What I would like to have is a bright tone in the heel up position and a muddy tone in the heel down position. That's what I meant writing longer sweep range(maybe I should've used the term wider).

[$uperpuma]

move your foot slower ...teehee

[Paul Marossy]

Try removing all of the rubber bumpers and adjust your footswitch accordingly.

[jonathan perez]

^^^^^ that should do alot, actually.

if that doesnt work, try a 470ohm resistor in place of the 510 ohm. that should give you more bass. a .015-.022 should give you a pretty large sweep, but youll get more treble with .015 and below.

[minimal]

And how would a different inductor affect this? Would lower/higher inductance do any better?

[Paul Marossy]

And how would a different inductor affect this? Would lower/higher inductance do any better?

It won't increase the sweep range. That's what you're after, right? The only way to do that is to make the pot go thru more of its possible rotation, hence my comment to remove the rubber stops.

[jonathan perez]

an inductor with, say 600mH will sound fatter, versus a 500mH.

a stock crybaby/vox inductor/dunlop fasel has a resistance of like 18 and below, right?

where as a reproduction halo is around 30.

[John Lyons]

Like paul said and zjokka  before him, the sweep or pot travel is small in most wahs. There is some of the pot travel at the begining and end that does not get used. To get more of a sweep you need to change the way the wah rocker pedal works. It's a mechanical issue.
If you remove the rubber bumpers under the rocker pedal you get a greater travel distance and a greater pot rotation.
ANother way to alter the rotation and how much treble verses muted sound you get is to adjust the gear on the pot and the rack which spins that gear. For maximum treble you want to adjust the rack and gear somthat when the pedal is fully pressed down the gear makes the pot turn all the way to it max rotation. It's takes some adjusting but you can do a lot by just doing that.
Wahs are mechanical beasts. Setting one up the way you like is not only electrical.

John

[R.G.]

The sweep range of an inductor wah depends on how much gain the first transistor has. The emitter cap of the second transistor is multiplied by the gain of the first transistor. More gain, more capacitive multiplication, and more range. The wah pot can't possibly make the range wider - all it does is select points inside the maximums set by the gain. Using less of the pot sweep restricts you further, of course, but the more first stage gain, the wider the range.

There is a point of diminishing returns, of course. The frequency of the LC circuit varies as the square root of the product of L and C. So with a fixed inductor, the frequency range varies as the square root of the multiplied C. Doubling the gain makes the effective max C twice as big, but gives you only 1.414 times the frequency. Quadrupling the gain gives you only twice the frequency sweep range. And large gains can introduce other problems as well.

See "The Technology of Wah Pedals" at GEO.

[$uperpuma]

I love the "The Technology Of..." Articles... I have learned a lot from them and sometimes I have to revisit them, to try to  wrap my head around more of the information that went over my head the last time... We appreciate it, RG.

[Paul Marossy]

To get more of a sweep you need to change the way the wah rocker pedal works. It's a mechanical issue.

That's the simplest way to attack it. That's one other reason that I like the Maestro Boomerang - it's got a lot of sweep due to how much the treadle can go up/down. Anyhow, in the CryBaby, removing those rubber bumpers can give you up to 5/16" or so more travel, and hence increased sweep range. Doesn't sound like a lot, but it can be noticeable if the pot is adjusted accordingly.

I love the "The Technology Of..." Articles... I have learned a lot from them and sometimes I have to revisit them, to try to  wrap my head around more of the information that went over my head the last time... We appreciate it, RG.

Yeah, same here. 

[John Lyons]

Well... My point was that if the pot isn't traveling the whole range of rotation then you aren't getting the whole range of the effect.
More pot travel = more range, no? You can of course alter the range of sound electronically but it may just be a matter of adjusting the pot, rack or rocker travel distance (removing bumpers etc).

John

[R.G.]

And your point is correct. There is an existing range that the electronics already provide. The pot can adjust the output sound from the bottom to the top of that available electronic range. If your pot does not rotate its full mechanical (and presumably electrical also) rotation, then you are not using as much of the electronic range as you might. In that case, increasing the pot travel will use more of the available electronic range. If, for instance, the pot only rotates 1/3 of its total resistance as a result of the mechanical limitations of the rocker and rack, then of course you are getting less than the full electronic range. In this case, diddling with the mechanics to let the pot rotate more will make more of the existing electronic range usable.

I was pointing out that there is an electronic limitation on the absolute width of the range regardless of how much of it is being used by the pot. If that electronic range is too small, no mechanical adjustment will help. In that case you can make the potentially available electronic range bigger or smaller. The pot's travel then selects a portion of that available electronic range up to but never larger than the available electronic range.

[Paul Marossy]

The pot's travel then selects a portion of that available electronic range up to but never larger than the available electronic range.

Yeah, and if you go larger, then you lose the wah effect or even your signal. This has happened to me with the Boomerang circuit.