Wah Project Advice Needed

[Jdansti]

Finally, Craig Anderton had a little article in Guitar Player way back about using an optoisolator to replace a scratchy pot in a Clyde McCoy wah.  Once you have a single, easily replaceable pot electronically controlling another device, that opens up possibilities for tweaking taper, range, and such.

That reminds me that the other day I picked up a few LDRs out of some bins at an electronics surplus store. There were several different looking models just loose and unlabeled.  When I got home and played with them, some had higher resistance when exposed to light and others had lower resistance. So if you had one pot driving a light source, the uppy and downy LDRs would cause the filters to go in opposite directions.

[Ronan]

Regarding two pots sweeping in the same direction, but slightly offset, I imagine this almost sounding like two guitars playing the pitches and timing in unison, but the two wah sweeps not being in unison.

This thread has an example of 2 filters sweeping in unison, set at different frequencies, in parallel. I see you've been there but just thought I'd point it out, in the light of this thread.
http://www.diystompboxes.com/smfforum/index.php?topic=98304.0

A breadboard works well for these type of experiments, the most common filters used are MFB filters (multiple feedback filters) because they are cheap to build, and usually of a bandpass design in the case of the EHx Talking Pedal and the Colorsound Dipthonizer. Wah circuits are low pass with a resonant peak near the cutoff frequency as shown in RG Keen's Technology of the Wah. 2 wah circuits may well sound better than 2 MFBF circuits, I haven't heard of anyone trying it. There is lots of info out there, it is a wonderful avenue to explore IMO, and I find experimenting helps towards understanding that info. I believe it is a DIY area that still has a lot more room for more development.

Edit: http://geofex.com/Article_Folders/sing-wah/sing-wah.htm
http://www.geofex.com/article_folders/wahpedl/voicewah.htm

[Jdansti]

I had missed PJP's suggestion of dual pots sweeping against each other on the bass balls.  Great minds think alike! 

Thanks to the references on RGK's wah theory. I learned something.

Thanks also for the info on MFB filters and low pass filters. I'll have to research these.

[Jdansti]

I received the Bad Dog Wah today and it doesn't sound bad for an used but unused metal $25 wah. I can't believe the guy I bought it from on eBay didn't charge for the $11.36 shipping!

I did a side by side test with my mid-70s Thomas Organ wah. The BD wah didn't have the same range of sweep on the high end compared to the TO wah.

Here's the PCB and pot:





I was surprised to see the E50217-06 PCB in a Washburn product, but I guess they just bought Cry Baby boards and stuck them in the enclosure along with a cheap pot. Does anyone recognize the pot?

[Ronan]

Interesting inductor, looks like a toroidal one. You might get more high end sweep if you make sure the pot is getting close to max rotation at the toe down position. If you adjust the pot be careful that the pedal at full toe down position (and engaging the switch/hitting the rubber stops) is not trying to drive the pot past its max rotation point. Looks like its in excellent condition, looks nice.

[B Tremblay]

Ian, did you ever get a chance to try that modified Bassballs schematic that I sent to you, or even just the filters?  I felt that making them both a true twin-T really fills out the sound.

[Jdansti]

Thanks Ian. I'll play with the pot position to see if that makes a difference. One thing I don't like about the BD is when I bring the toe all of the way down, it makes a loud clack when it hits the switch actuator and presses it in a little.  It doesn't go so far as to activate the switch, but it's as annoying as hell.  You still have to really mash on it to activate the switch, so I don't know if I can adjust it to fix this problem.  My other wah doesn't do this. I haven't used any other wahs, so I don't know if this is normal. 

[Ronan]

Ian, did you ever get a chance to try that modified Bassballs schematic that I sent to you, or even just the filters?  I felt that making them both a true twin-T really fills out the sound.

No, unfortunately I didn't Brian, I printed the schem and had everything ready to modify the breadboard, and other things came up and distracted me. I still have the schem and breadboard, and need to try it out, I will let you know when I do. Interesting comment that it fills out the sound, as that is exactly what I am looking for.

John, there is supposed to be a small piece of felt stuck under the pedal that comes into contact with the switch, the felt takes away the clack sound. I'd guess your felt is missing, and that has made it more difficult to switch it, because the pedal now has to travel down further than it used to in order to activate the switch. Also the switch can be adjusted up and down in height using the mounting nuts to adjust the position where it is activated.

[Jdansti]

Thanks Ian. I've got some felt I can add. I'll check the treadle travel too and switch height too.

[joegagan]

I received the Bad Dog Wah today and it doesn't sound bad for an used but unused metal $25 wah. I can't believe the guy I bought it from on eBay didn't charge for the $11.36 shipping!

I did a side by side test with my mid-70s Thomas Organ wah. The BD wah didn't have the same range of sweep on the high end compared to the TO wah.

Here's the PCB and pot:





I was surprised to see the E50217-06 PCB in a Washburn product, but I guess they just bought Cry Baby boards and stuck them in the enclosure along with a cheap pot. Does anyone recognize the pot?

this is not a dunlop board, or a print of a dunlop board.. they did steal the basic gcb95 layout and used the crybaby name illegally. it is very easy for these companies to crank out their own layout and board.

[Jdansti]

@Joe:
Does your BD have the same board?

How about the pot? Crap?

[joegagan]

mine looked exactly the same, the parts are all scattered now but i recall it was the same. inductor sounds ok. pot was crap.
this washburn was a good deal for the shell. the bottom plate is twice as thick as the crybaby bottom plate, but made out of the weirdest metal you've ever seen.
still,
for the $$, anyone looking to do a wah project you can't beat a 25, 30 or even 40 dollar used dunlop, especially if it has the hotpotz2, those pots alone sell for no less than 25 on ebay new, and since they hardly wear out you are in like eating bacon in a hottub.

[joegagan]

while i'm on the topic, don't forget, a stock GCB95 is a great sounding wah just like they make em ( dunno bout the chinese made ones tho).

in this video, i compare a modded crybaby to a bonestock 2004 dunlop CB

[Jdansti]

Thanks Joe. Very nice!

[garcho]

I wonder what two wahs would sound like working in reverse of each other. When one goes up, the other goes down at the same time and vice-versa.

Not to toot my horn, but here's a link to a thread I started (not a thread yet, only one post  ) that's about a pedal I'm making for the Turkey contest that's two op amp style bandpass filters controlled by LDR LFOs, in parallel or series. Putting the filters and LFOs in parallel and close to sync and really slow makes for some great phasery sounds. Putting them in reverse (although not locked with a timer. ...yet) of each other at the same frequency almost cancels out the LFO modulation, but adjusting each to a different band sounded really cool, especially in parallel. Cheap, no inductor, no expression pedal enclosure, for better/worse. The vowel sounds are great. Lots of yoy and aye. Easy to breadboard too. And only 200 calories! Anyway, I messed around using it in series with a Morley wah, and then lots of compression, and it was also cool, but I wish I could've had the Morley parallel with the other filters, for a total of 3 in parallel. 3 filters in series act almost like a weird VCA with LFO modulation. Made me think cascading 4 or 8 filters in parallel with LFOs could make for some real goofy faux phaser stuff. Anyone know of that type of thing? I'll try throwing one together in the next few weeks on the ol' breadboard.

[AudioEcstasy]

I would just buy a crybaby and gut it. YOu'll get the die-cast enclosure and it can't be expensive second-hand

[pinkjimiphoton]

fwiw, the pyle and the rogue are both about the same. neither is very studly, and the switch position kinda sucks. i've used both shells, the one with the volume slider on the front is the better of the two.

[Jdansti]

The Bad Dog is pretty sturdy, it just needs some adjustment.  I still like my 1977 Cry Baby, though. It's still kicking after 35 years!  Here're the old Cry Baby guts:





The Pot

[joegagan]

beautiful guts. nice photo work
that pot is very likely original, centralab (134), 33rd week of 77. in my travels, i have found that only around 10% to 30 % of the 70s thomas wahs had SOD inductors. one of the stompbox book articles mentioned that TDK had undercut the price of the SODs by quite a bit, but that they sometimes could not keep up with demand. i have a theory that thomas would only use the SODs during the times they couldn't get the TDKs.

i also wonder if thomas requested that tdk stop using the 'japan' stamp on the inductors ( public perception of japanese electronics wasn't as good then), the japan stanp shows up on earlier (72-74 ish ) but not later.

the wire wrap post method of wiring is fun to look at. take a look at this ATD WV1, which is the maker brand of the boomerang. the wiring on this is so elegant and clean, i love it. the wire wrap was so well done, no soldering needed! also an early use of power supply input - '75.

[Jdansti]

Thanks Joe. Yeah, it took me awhile to get that shot of the markings on the pot. I was using my iPhone camera. I had to block the reflection of the inside of the enclosure with some masking tape in order to see the numbers.

Nice wire wrap on the ATD.  I don't know if TO soldered the posts on mine or if I did it many years ago.

I haven't decided what I'm going to do with the Bad Dog, but I'm thinking about adding a CV jack that would open the circuit to the pot when a jack is inserted and allow me to use external control. I've been doing some research on gyros and accelerometers. I might make a very small control box that would attach to the guitar and let you control the wah by tilting the neck up and down. I thought this was a new idea until I did a search on the forum and found someone else talking about it.

Another idea for external control is to use a small through hole pressure transducer. I would wear the controller and have a small tube that goes from the transducer to a mouthpiece, maybe something similar but much smaller than a sax mouthpiece so I wouldn't have to hold it with my hands. Blow gently and the wah tone goes up.

I've got a couple of other controller ideas brewing.