Building Wah Pedal from volume pedal

Hemmel · July 02, 2013, 02:25:37 PM

Hi guys !!

My brother gave me his old passive volume pedal. It's simply input/output jacks, grounded to a metal plate, and a B100K pot in the middle. It's a bit stiff (mechanically) to my taste but I'd like transform to a wah pedal.
I found the Colorsound Inductor-less Wah here http://www.beavisaudio.com/Projects/ColorsoundWah/index.htm (the first schem). There's a volume pot at the end that I do not want to put in my pedal. Could I simply remove this pot and go straight to output ? Would I need to change the last resistor's value (the 47K) ?

I'm going to breadboard the circuit first to try and tweak it but I wanted your feedback first... Thanks !

GGBB · July 02, 2013, 02:53:47 PM

Yes, you can leave it out, and if you do, you can change the 47K to 33K, but that probably won't matter much. However, you may want to use a trimpot for the volume control rather than omit it entirely since it will allow you to adjust the output level to match the input.

Hemmel · July 02, 2013, 02:55:40 PM

That's a super good idea and I have an A100K trim pot lying around somewhere... Thanks GGBB !

I also noticed there's a covered-up space for a jack on the pedal casing. I'll drill through the plastic to set the DC jack in its place.

Hemmel · July 03, 2013, 08:54:56 AM

Well....
Breadboarded the circuit and it's not working. Even with volume pot at 100%, when effect is applied I get a 25% volume cut and the wah pot does nothing.

Kinda frustrating...

mistahead · July 03, 2013, 09:05:05 PM

Beavis is awesome, but check some alternative schematics/layouts - there are heaps for this effect out there and it is verified in many of them.

I can't recall entirely but I remember this being a fiddly "Twin T" filter and Geofex Tech of Wah page is VERY useful.

Just leave the VR for volume off entirely (remember if you're going to replace it with a trim to make it a voltage div. to gnd) for testing.

deadastronaut · July 04, 2013, 05:28:23 AM

check out the morley classic wah...

http://www.morleypedals.com/downloads.html

very simple but great wah circuit...better than the colorsound inductorless, which distorts too easily imo...been there..

Hemmel · July 04, 2013, 11:00:42 AM

(My 100th post ! Yay!)

I'll check out the Geofex page, thanks for the tip, mistahead. I tried replacing the volume pot with a trimpot, and also tried removing that pot altogether. Always had the same output, although at different volumes. Wah pot changes nothing.

Thanks Rob, however the classic wah from Morley uses a LDR, I'd like to find one which uses a B100k pot (because the old casing I have has a setup with a B100K pot already installed). Perhaps I could replace that LDR with the B100k ? I could then remove the lower section (where L4 and L5 are)

joegagan · July 04, 2013, 12:40:13 PM

looking at the classic wah from morley, yes , you would replace the LDR setup with apot wired just like the colorsound you linked to in beavis' page.

the series 33k in beavis diagram may or may not be helpful, experiement with that. i did not read his text, but i suspect the 33k is to tailor the response of the pot in some way.

Hemmel · July 04, 2013, 01:34:11 PM

Joe, I think you're talking about R8 ? The one just above the wah pot ? (Because there's another 33k, R7)
I'll try to remove it and/or change its value to see if it has any effect on the wah pot...

JebemMajke · July 13, 2013, 09:07:30 AM

Hello, I;ve just made pcb in eagle for this wah. It's based on this schem

which I've found on Russian pedal building forum. It's going to be truebypass as well.

I'm going to use mini dpdt momentary switch so that the pedal is engaged only when i put my foot on it. And i would like to use it as volume pedal as well. So can someone explain how to wire Wah/Volume switch. Dpdt if possible.

JebemMajke · July 13, 2013, 10:29:31 AM

I think i figured it out. Please do feel free to correct me.
http://i1249.photobucket.com/albums/hh505/JebemMajke/WahVolswitch_zps8e9e7b5a.png

Hemmel · July 29, 2013, 03:17:32 PM

Ok so I'm back on this project. I'd like to have your feedback on my first attempt at creating a stripboard layout.

EDIT : Image updated with corrections.

Schematic can be found here. Notice that I changed the setup according to what was said in previous posts of this thread (i.e. swapping LDR for a wah pot).

I put everything down on paper first, then copied it on DIYLC. It seems like there's a huge waste of space, especially right above the IC. I don't have a good eye for these things.

The layout hasn't been tested yet.

Thoughts ?

Hemmel · July 29, 2013, 03:43:26 PM

Well I just noticed I could move R7 to the upper-left of C7, thus freeing column "O". I could then move the jumper on "P" as well as output and wah connections, one column to the left.
16x12 instead of 17x12.

EDIT : There's also a cut that shouldn't be there. The one next to R5. Why did I put it there ??

EDIT #2 : New image (corrected) on previous post.

deadastronaut · July 29, 2013, 04:39:55 PM

@marc

looks ok at a quick glance,

tip: use the ''transparency ''alpha' in diylc, it just makes it easier to see cuts under components etc.

and use the ''cut'' red square with dot thingy for cuts...

Hemmel · July 29, 2013, 05:22:12 PM

Quote from: deadastronaut on July 29, 2013, 04:39:55 PM
tip: use the ''transparency ''alpha' in diylc, it just makes it easier to see cuts under components etc.

and use the ''cut'' red square with dot thingy for cuts...

Thanks Rob. I was surprised that even if the icon for cuts looks like the red square, it's not what was shown on the layout

I'll need to look through the software a bit more.

The iron is heating up, I'm testing this layout right away.

Hemmel · July 30, 2013, 10:05:32 AM

Quote from: Hemmel on July 29, 2013, 05:22:12 PM
The iron is heating up, I'm testing this layout right away.

Well, no 1.2M resistors, no 5pF caps, I'm also out of 6.8nF... so testing of the layout will have to wait for the weekend.

deadastronaut · July 30, 2013, 10:19:18 AM

1M/10pf/4.7n will do..

or socket them for now..

Hemmel · July 30, 2013, 10:39:34 AM

Quote from: deadastronaut on July 30, 2013, 10:19:18 AM
1M/10pf/4.7n will do..

Yeah probably. I'm just a bit worried because I changed a few values on other effects and the end result didn't sound right...

Quote from: deadastronaut on July 30, 2013, 10:19:18 AM
or socket them for now..

That's a good idea !

BTW, right before the wah pot (or the LDR on the original schematic) there are 2 caps, 6.8nF and 2.2nF. What if I changed these to 2x 4.7nF ?

deadastronaut · July 31, 2013, 08:07:19 AM

i think that will make the sweep too even...

socket those too...then you'll be able to experiment with the sweep.

Hemmel · August 07, 2013, 08:29:35 PM

I'm building this right now and I'm kind of hesitant on the pot lugs.
Pretty sure lug 1 goes to ground.
But 2 and 3 ... how do I short them ? 1-2, 3 or 1, 2-3 ??
Any quick thoughts before I solder ?

EDIT : OK so I tried what I thought was good. 1 to ground, and short 2-3 together. Now the wah sound is there. Success !
Well, kind of...

There's a sort of "kiss" sound when I step fully on the pedal. It's really weird. The only 2 I changed were C6 is 0.002 (instead of 0.0022) and C4 is a socketed 33pF (still waiting for my 10pF to get in from Tayda)
Do you really think that 23pF difference could cause this ?

News:

Building Wah Pedal from volume pedal