Joe Hart's Wacky Wah Adventure

[joegagan]

that quick jump is possibly being caused by the log taper of the hotpotzII, same would be the case with other common wah pots.

play around with rasing the 1.5 k resistor, this is rumored to smooth the transistion. lots of good clues in gus'post above as well.

[Joe Hart]

I soldered a pot to where the 33K "Vocal" resistor was and my wah is being a "reverse volume pedal" again! Even when I set the pot to about 33-45K -- it makes no difference. What component could be messed up to make it a "reverse volume pedal"? I know if the 4.7uf cap is out of the circuit it will be a volume pedal and not a wah, but mine's volume-ing in reverse! Is that normal?
-Joe Hart

[Joe Hart]

play around with rasing the 1.5 k resistor, this is rumored to smooth the transistion.

I did that and it helped a little. I think it more just added a bit of mids and therefore makes it seem like it's a smoother transition (like EQ-ing something can make it "jump out" of a mix or "fall back" in the mix). I didn't find that it actually changed the perceived taper.

But I still have a bunch of things to try (once I get it wah-ing again!).
-Joe Hart

[Gus]

About the 1.5K #36 in the wha patent.  page 4 column four top right

The wha patent has a lot of information.

All the wha modders need to do is read that patent and R.G.s write-up and do experiments.

[Joe Hart]

Thank you, Gus. I checked out the info you posted and some of it is a bit over my head, but I'm working on it! Thank you for the help!

And I can't forget to thank you, Joe Gagan!

-Joe Hart

[Joe Hart]

I got my wah working again... again! 

I checked all of the connections and let me tell you, the solder pads on the Dunlop PCB are FLIMSY! I modded a couple Vox wahs and didn't have any issues. Right now, I have four jumper wires under the board because of solder pads that lifted! And I've only changed six components so far. Argh!

Anyway, it's sounding pretty decent although I sometimes have to kick the pedal a time or two to get it to wah! I mean kind of bumping it on the side of the pedal to get the wah working. There's sound and everything, but it just doesn't really wah, then I give it a couple of kicks and suddenly it works. I'm wondering (due to some snooping around with the components) if the cap that looks like a big rolled up silver sheet of plastic is faulty? It is a "reclaimed" cap and about 40 years old, but it sounds great. Can these develop shorts of some sort that would make them "futzy"? If I tap on it, there's a "microphonic type noise" that comes out of the amp. But, of course, I can't isolate this one component from the board (short of desoldering it, adding longer leads and having it hang out the side of the pedal).

I've done enough damage to the PCB so far, and I am a bit hesitant to desolder a cap that may be fine (and sounds great) just to try another cap and then end up with the one that's in it now back in it.

Ideas of this microphonic issue I'm experiencing?
-Joe Hart

[Govmnt_Lacky]

Good to hear you got some positive results Joe! 

Have you considered just etching a new board and transplanting/replacing components so you don't have to deal with "flimsy solder pads?"


Good Luck 

[Brymus]

Yeah I would pin point which parts are gonna be auditioned and use sockets.

[Joe Hart]

Have you considered just etching a new board and transplanting/replacing components so you don't have to deal with "flimsy solder pads?"

I did, but most of the parts are staying where they are, and the wah has PCB mounted in and out jacks and power jack, and all the offboard wiring is with a harness thing, so etching a new board seemed like more trouble than it was worth... notice I wrote "seemed." Of course, now I'm not so sure! But, at this point, I've replaced most of what I wanted to anyway, so...
-Joe Hart

[Joe Hart]

Yeah I would pin point which parts are gonna be auditioned and use sockets.

I've never had a lot of luck with sockets! Maybe I'm using the wrong ones, but I solder them in, then with all the "in and outs" with the components, there ends up with too much stress on the solder joint (no matter how careful I am) and it ends up lifting the pad or some sort of problem like that. And I have the socket flush with the PCB and soldered in pretty good (or so I think). And if the part is a resistor, I usually just solder in a pot, then read the value I end up with, then solder in the correct resistor, so it's the same amount of soldering if I was to use a socket and the final resistor value. But, again, maybe I end up using the wrong sockets. Or maybe it's just me!
-Joe Hart

[Joe Hart]

I tried the "vocal" mod and found something fairly interesting. I replaced the 33K resistor with a pot and beneath about 20K, the wah didn't work so well (which makes sense because the "vocal" mod says to increase that resistor to double or even triple the value), but above about 20K I found NO DIFFERENCE at all. I even tried 1M and it still sounded fine. I've never heard of this. I know some older pedals had as high as 100K in this spot, but many people find this too high. I pretty much found that it's either too low and the wah sounds pretty weak, or it's high enough that the pedal sounds good again. In other words, I noticed no difference between 33K and 68K and 100K and even higher. So I just stuck a 100K (which actually reads about 112K) in there. Maybe it's just me? But I wanted to report my finding.
-Joe Hart

[joegagan]

hmm joe, i don't know what to make of your resistor changes and the results. i usually stay with 33k in that position.

i am breadboarding gus' circuit mentioned on the previous page, will let you know how that turns out. i really like his approach to letting each transistor bias independantly. hope to get back to it tonight.

meantime, check out where my wah adventure led me if you have 50 seconds.

http://www.youtube.com/watch?v=MzcI3m_rU-c

[Joe Hart]

meantime, check out where my wah adventure led me if you have 50 seconds.

http://www.youtube.com/watch?v=MzcI3m_rU-c

Okay. What do I need to mess with to get mine to sound that thick and disgusting!! :-)
-Joe Hart

[Gus]

Joe Gagan

Emitter followers can become unstable(google"emitter follower stability", this can be overlooked)look at page 4 of the patent, column 4 lines 22 and 23.  You might want to add a resistor between the EF collector and +9VDC, as seen in some wha schematics.  This is written about in the patent IIRC.  It will be easier to see with an oscilloscope at the emitter of the EF.  If you add something like a 1K you can adjust the EF emitter with one of the EF bias string resistors if needed.

The higher input resistance of the EF should allow the use of tapering resistor(s) on the wha pot/volume control.  Try the highest hfe you have(>500) something like a MPSA18 for the EF

The wha schematic is drawn up as a starting point.  As I have posted in the past it was inspired by threads and posts here from people like Paul M with their posts about the Colorsound inductor wha and boomerang wha.  The series input resistor value should be adjusted to taste.

You can adjust the first stage operating points with the * marked resistor(think distortion). You also have the damping resistor across the inductor and the 1.5K resistor to the first stage and the sweep cap value and type(ceramic might be fun X7R, Z5U type etc).

[joegagan]

Okay. What do I need to mess with to get mine to sound that thick and disgusting!! :-)
-Joe Hart

first, put two wahs in series and wah them at the same time-boosted by a fuzzy boost ( brontoboost set to stun on the clip). make the second wah in line a dynamic low voiced wah. this is done by increasing the Q cap to " large". to hear the  pain inducing earbleed treble, FF to:50 on this one        http://www.youtube.com/watch?v=hmHhGoF0Xfg  ( do not listen to this)

gus, thanks, i will read up on emitter follower stability. looking forward to hearing the results of your approach. i am starting with the schem as drawn so i have an idea the baseline. i also have a few key voicing areas in mind i want to tweak once i get the basic circuit working well.
just got a little busy this week, need to get back to the breadboard.
thank you for the schematic and the advice!

[Gus]

Joe G.

Do you have the dc resistance and inductance of the different inductors?  I simmed the circuit in LT spice and don't have any fasels etc to measure to model the inductor better.

If you add a 1K in the Q2 collector leg change the "top" EF bias string resistor from a 100K to a 120K.

[joegagan]

thanks gus,

here is a thread at the pedalworx forum where we did an evaluation/measuring of dozens of inductors.


george likes 40-50 ohm and very close to the magic 500 Mh, i agree but there are bizarre exceptions.
i have morley spec'd inductor 500mh, the factory morley schem lists the impedence at 12ohm ( four test units all measure within 4% of 12ohm), i really like the sound of one of them ( other three not so good?).

there is another commonly found inductor from the 90s that usually measures in the 650 Mh range(58 ohms or so) that i also like the sound of a lot.

thread: ( join up if you like the looks of it!)
http://forum.pedalworx.com/forum/viewtopic.php?f=4&t=2

[joegagan]

If you add a 1K in the Q2 collector leg change the "top" EF bias string resistor from a 100K to a 120K.

yes, i am aware of that , you taught me that a while back.

[Joe Hart]

put two wahs in series and wah them at the same time

I've been messing around with this idea and I like it! I'm starting to think that I'm trying to make my Cry Baby something it's not and this may be the source of my slight disappointment with it so far. I mean, there are some cool sounds coming out, but I want it to sound much more like Joe Gagan's clips of his Super Puke. So this leads me to wonder if there's a way to put two wah circuits in one shell and be able to run one or the other or both at the same time and control them (here's the catch) with the same treadle? Any ideas how I could do this, short of welding for another rack and pinion and pot and everything?
-Joe Hart

[SISKO]

http://geofex.com/Article_Folders/wahpedl/wahped.htm#twowahs