Hey everyone,
this is my first post on this forum so I just want to say hello. I've made a couple of DIY amps from AX84.com and would like to turn some attention towards stompboxes now.
I see that there is a bunch of reading I have to do, but I have a question regarding my Dunlop Crybaby GCB-95: The wah tends to work quite well in the treble range, but then transitions quickly into a muffled bass range. Really, this limits me to using the treble only. After having read the big article at GEOFEX about the Technology of Wah Pedals, one suggestion for a wah pedal only working in the treble range is that the inductor would be open. Does this sound like it would be my problem? Really, it is something that has been prevelant as long as I can remember, and I never stopped to think that anything would be wrong with it.
I'll continue to look and I plan to open the pedal up over the weekend to take a look see, and I will continue to look throughout this board and at other sites, but if anyone has any suggestions I would like to hear them.
Thanks again,
Jude
p.s. Happy St. Paddy's Day to any Irish out there!
It sounds like you're describing the typical muddiness in the foot up (back) position. You could try upping the value of the 1k5 resistor for more midrange. Try these sites also:
http://homepage.ntlworld.com/s.castledine/greenfuz/wah.html
http://www.runoffgroove.com/wahmods.html
http://www.happybob.com/marc/pot_adjustment_procedure.htm
http://www.realmccoycustom.com/ADJUSTMENTHELP.htm
Hi. The inductor is definately connected if you get the moving filter effect (ie a wah).
The Crybaby has strong treble compared to the JH-1. To convert to the JH-1 circuit only involves adding 2 extra capacitors. It's a worthwhile change in my opinion. The relevant schematics are on the web.
The other mod that I'd do is add an output buffer so that the wah will work with a fuzzface and other effects with low input impedance.
Welcome Jude. :D
I don't have any advice, but just wanted to say hi anyway.
Take care,
-Peter
Thanks all for the advice and the welcome. I'll open the pedal up soon and will let you know how I get on.
- Jude
Your problem is largely down to the gain of the circuit. Dunlops have high gain MPSA18 transistors and a 390ohm emitter resistor on Q1. '60s/'70s Vox and Crybaby wahs have lower gain transistors and a 470ohm emitter resistor on Q1, so they have much less bass and a more balanced sweep range.
Try swapping the 390ohm resistor for a 510 or 560. The Vox reissue has MPSA18s and a 510ohm resistor on Q1.
Stuart
The output buffer, in case you're interested.
(http://members.optusnet.com.au/~jethro.dog/mypic120.jpg)
cheers
Quote from: StuartYour problem is largely down to the gain of the circuit. Dunlops have high gain MPSA18 transistors and a 390ohm emitter resistor on Q1. '60s/'70s Vox and Crybaby wahs have lower gain transistors and a 470ohm emitter resistor on Q1, so they have much less bass and a more balanced sweep range.
Try swapping the 390ohm resistor for a 510 or 560. The Vox reissue has MPSA18s and a 510ohm resistor on Q1. Stuart
I never thought of that, simple. I've always thought of that resistor to
increase bass and gain, never to lower it. My suggestion wouldn't have addressed the mudiness, and the increased the midrange probably would have made the sweep range even more lopsided, right? After the gain and base issues are sorted, then the 1k5 between the base of Q1 and the inductor would be adjusted to taste if needed.
Stuart, if the MPSA18's are replaced with 2n3904's or similar low gain, how much adjustments to the values will be required? Any low gain canidates for recommendation? Thanks for the tips.
Fret:
Doug Hammond came up with a fatness mod to the Crybaby. Oddly enough, it uses 3904's. You might want to have a look...
Quote from: DavidFret:
Doug Hammond came up with a fatness mod to the Crybaby. Oddly enough, it uses 3904's. You might want to have a look...
Yeah, my dunlop wah came with 2n3904's in it.
I would suggest playing around with R & C values and tuning the filter and gains to your liking, based on R.G.'s article. There is a lot of "bang for the buck" in that area. A lot of people immediately assume they need new inductors or something to get the sound they want. You would be surprised how much you can improve the tone of a dunlop wah with some simple re-tuning of the filter.
Doug
Doug:
Since you're here, perhaps you'd answer a question:
If I build a wah from scratch using your circuit, how well do you think it would work with one of the Radio Shack transformers as the inductor?
Or should I just bite the bullet and find a Fasel?
Quote from: DavidDoug:
Since you're here, perhaps you'd answer a question:
If I build a wah from scratch using your circuit, how well do you think it would work with one of the Radio Shack transformers as the inductor?
Or should I just bite the bullet and find a Fasel?
I have no idea... :D
I have never built a wah from scratch, just modded the one I already had.
Doug
Buy the Fasel. That's about as close as you're going to get to the original, coveted inductors used in the vintage wahs. I also have heard that the ones Stuart Castledine makes are nice (I think that is one cat who makes some inductors to vintage specs - I know there are a few out there who make them - Teese is another, I believe)
I'll second what Doug said. Just changing a few resistors and caps can really change the sound and improve it quite a bit (or at least make it more to your liking).
Well now! Thanks everyone for your suggestions.
It would seem that the first answer I got, from Fret Wire, pretty much nailed it on the head. The Dunlop GCB-95 does sound, to me, to be muddy in the back position.
I say this now because I went to Guitar Center this evening with my own wah to compare it to new versions they have on hand. The newer GCB-95 sounded pretty much the same as the one I have: muddy in the back position, too trebly in the forward. I compared then with a Dunlop Jimi Hendrix, and that sounded much "fatter": more definition in the bass and no ice-pick-in-the-ear highs.
Oh well, at least I know my pedal isn't broken; I just don't like it so much anymore.
I will try some of those mods you each have suggested, though, one of these days.
Thanks again,
Jude