Wah Pedals...

[isher1992]

I've been thinking about building a wah pedal after not touching one in years...

I'm looking at a few schematics around, and I know the unbuffered wahs tend to have a bit more bass content, so I thought about building on a Tonepad PCB.  Aside from some of the more typical wah mods (resistors and sweep cap and inductor), what about those tiny input and coupling caps?  Would increasing those to double or more (0.1uF input for example) help feed more bass through?

I was thinking of a 0.068uF sweep cap (like the GCB-100) with a 100K ICAR taper...

Here's the pdf for the Tonepad wah:  http://tonepad.com/getFile.asp?id=114

[roseblood11]

I know the unbuffered wahs tend to have a bit more bass content

That's what they said on da interwebs, right?

[PRR]

It's complicated.

For 37 cents you can just try it.

[Elijah-Baley]

This is an interesting web site: http://www.electrosmash.com/crybaby-gcb-95

This is the standard Cry Baby GCB-95 schematic:


For a more Fat/Gainy/Bass sound you can try to decrease the gain resistor. R4 in the schematic.

The sweep cap doesn't add bass, not exactly, but it moves the range of the sweep toward bass frequency. Ideal for bass guitar, indeed you named the GCB-100, the Bass Cry Baby.
You should make some test with the caps Cin1 and C1.

I have a Cry Baby GCB-95 with true bypass mod, and I still have to apply some mods. These are the mods I found, and I repeat: I didn't try them yet by myself.

Volume Pedal Mod: If you disconnect the ground of the C3 cap 4.7uF you get a volume pedal. Not perfectly, seems to be a loss of high when you low the volume, and the volume doesn't fade out completely. It gives a sort of swell effect.

Sweep Cap: Changing the value of the C2 cap you modify the range of the sweep. (Example: 0.01uF higher frequency as in the standard Cry Baby, 0.068uF is the bass guitar frequency). A DPDT switch or a rotary switch can give you more options.

Gain/Bass mod: Decreasing the R4 value you get more bass and volume, and a bit of more gain. A 500R pot could be a versatile solution.

Vocal Mod: You can change the value of the R7. 33k is the standard, 68k gives a more vocal sound. 100k is the value of the Clyde McCoy setting. A 33k resistor + 50k linear pot or a an only 100k linear pot can give you a adjustable range.

Midrange Mod: Increasing R2 you get more mids. Usually nobody goes over the 2.4k. You can try resistor between 1.5k (standard) and 2.4k. Or 1.5k + 2k Linear pot to have an adjustable setting.

Just for start you can test some part using socket pins on the board and tell us how much difference make those mods.

[Renegadrian]

I know you want to use the tonepad pcb, but I'd like to suggest you another very sweet wah, the morley one - I built it and posted a vero layout in my gallery. It's so easy to build! I loved its sound!!!

[thermionix]

I do believe this schematic from Electrosmash contains an error.  The 1k "Rin3" is in the wrong place, in an actual GCB-95 it's in series in the +9v rail and feeds all three transistors.  Not such a big deal, but could cause some real confusion if someone was looking to remove or bypass the input buffer.  It may be something that was changed by Dunlop at some time, I suppose the wah would work either way.

[PRR]

> The 1k "Rin3" is in the wrong place, in an actual GCB-95 it's in series in the +9v rail and feeds all three

If so (I believe you), we would expect >10uFd from there to ground.

Or not: letting the three stages leak to each other could do something, and could be interesting. But the cautious engineer doesn't like to hang three things on one nail.

[pinkjimiphoton]

the only real dif between the dunlop guitar and bass wahs is the bass has double the values on the input and output caps. so yes, you can mess with them to good effect, tho i don't think it makes a hill of beans difference in the tone of the wah. bigger caps allow more bass, more bass can cause instability and motorboating, so try not to get too carried away.

but yeah man, that's really about all there is to it if ya wanna do that.

my humble suggestion, if ya wanna use your wah before a fuzzface, say, is to wire in around a 50k pot (can be a trimmer) wired as a variable resistor in line with the output of the wah board before it hits the switch.
it's like a "passive buffer" (no such thing really lol, but..)... you can dial in the resistance until the wah and fuzz play nice together.
in my experience, it works better than all the so called "wah buffers" that people try.

i mounted the pot on the side of my crybaby's shell, along with a dpdt true bypass. that way i can put it before or after fuzz , stock or modded.

as for other mods, go to geofex.com and read the technology of the wah pedal. ya can't go wrong with that synopsis.

fwiw, i did the gain, mid and vocal mods and didn't bother nuking the buffers in mine and t/bing it.

also... lifting the ground on the electro won't really get ya a volume pedal. it's more like a broken tone pedal. it won't go all the way off, and it won't really wah, but it WILL get louder and brighter from heel to toe.

but not in a particularly good way imho.

i wanna suggest talking to joe gagan too, and investing the 20 bux or so in one of his "smooth" pots... he uses top notch military grade components, and a special gear where ya get almost 90% of the pot sweep instead of the usual 60 some percent. i use his pots in everything i build that has a treadle. the best i've found.

and no, i am not being paid for this endorsement of a fellow forumite

[thermionix]

> The 1k "Rin3" is in the wrong place, in an actual GCB-95 it's in series in the +9v rail and feeds all three

If so (I believe you), we would expect >10uFd from there to ground.

Or not: letting the three stages leak to each other could do something, and could be interesting. But the cautious engineer doesn't like to hang three things on one nail.

Yes, like this:



I have a GCB-95 here on hand and it's done this way, though maybe Dunlop made a change at some point, I don't know.

[PRR]

> it's done this way

Yeah, their 220uFd is my ">10uFd" only bigger.

[Elijah-Baley]

the only real dif between the dunlop guitar and bass wahs is the bass has double the values on the input and output caps [...]

I always thought the difference between the guitar and the bass version of the Cry baby was the sweep Cap: 0.01uF - 0.068uF.
But definitely you have to make some test with the input cap.