# NPD: Thomas Organ Cry Baby



## TWRC (Apr 22, 2011)

I've never been a huge wah user; but when I do use them, I like to use them in conjunction with fuzz pedals which can cause some major headaches in the buffer and range department.

With my new group, I've been slowly incorporating the wah into my playing and have been using my Vox 847 that I have modded with true bypass, gain, mid and vocal mods. I haven't been too happy with the sound as the noise at certain points can be unbearable and the sweep range is very narrow when using fuzz (it works fine with just OD).

After explaining the situation to a friend of mine, he asked me if I was interested in buying his '76 Thomas Organ Wah from Chicago with a stack of dimes inductor. The great thing about this wah is that he had already installed the FoxRox buffer in it and wow, what a difference! I plugged it in and immediately got the wah range that I was looking for and without the squealing noises associated with my fuzz pedals - needless to say, I bought the pedal. The wah itself sounds a lot sweeter and more open than the Vox. The only thing that I didn't like about it in comparison was the fact that it didn't have as much bass as the Vox (more on that later).

So here's the skinny. The pedal isn't completely stock as my friend had turned it into true bypass added the buffer and a new ICAR pot. I also noticed something funny about the enclosure itself in comparison to my 847. The physical sweep range of the pot is less than the Vox just due to the treadle positioning. As the Thomas Organ sounded better overall, I swapped the guts into the Vox enclosure and was instantly pleased with the added range.


































Now, back to the bass question. I'm no good at reading schematics, so if anyone can help me here, that would be great! I know that I can swap the 470k resistor in Q1 with a smaller value to increase bass, but which resistor is it? Is it the one in the upper left corner in this diagram?


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## ElectricMojo (May 19, 2011)

Really nice. Congrats!


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## mhammer (Nov 30, 2007)

Start here: http://www.geofex.com/article_folders/wahpedl/wahped.htm


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## TWRC (Apr 22, 2011)

Holy crap! Thanks Mark. Some of that made sense to me and actually showed me that I was looking at the schematic in the wrong way. Looks like I had the right position for the resistor, but that was more blind luck than anything. 

I like the idea of having a trimpot there to further shape gain / bass so I might do that. The wah itself sounds amazing, but just lacking that extra oomph which I suspect was lost due to the true bypass mod.



mhammer said:


> Start here: http://www.geofex.com/article_folders/wahpedl/wahped.htm


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## mhammer (Nov 30, 2007)

I made myself a wah from largely scratch, using a Fasel-like inductor I bought from a local place for a $1, before they went under. It has the ferrite core/chassis, and is 900mh, with a tap around 760-800mh. Took me a little while to nail the right emitter-resistor value on the first transistor, but once I did it sounded great. Much more a "vocal" sound, like what what one normally hears from Jeff Beck, than a wacka-wacka porn-soundtrack sweep. You might think that an inductor that high would be way off, but a little bit of adjustment of the other component values, and you're in business.

I actually bought a couple of those $1 inductors, but haven't put the others to use yet. Steve Daniels at Small Bear sent me a wind-your-own inductor kit ( http://www.smallbearelec.com/servlet/Detail?no=368 ), which I have used, but have not yet managed to get anything more than 300mh out of. I've been gradually reducing the size of the magnet wire I use to wind the coil. At some point, I expect to "get in the zone". I'm just not there yet. It may be simply a matter of the winding method I'm using. I probably need a more stable and smoother winding jig than I currently use, which introduces a little more "scatter" than is appropriate.

The GEOFEX site has an incredible wealth of material for public consumption, an embarrassingly large amount of it written and/or drawn during boring meetings at his former employer. RG and I have been web-buddies since 1991. An all-round swell guy. We attempted to co-author a "Distortion Bible" about 5 years ago, but it faltered after a few back and forths. Perhaps we'll get back to it if I ever retire or semi-retire. He is presently the chief engineer for Visual Sound.


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## TWRC (Apr 22, 2011)

That's the thing I hate about wahs. Some of them are really thin and "porn"-like. I really like the vocal quality of the Colorsound wahs etc, but the pricetag isn't all that great.

I had every intention on playing around with the inductor on my Vox, but never got around to it due to having to compensate other component values has you stated - so I just stuck with it. However, a wind your own Halo inductor kit sounds like a pretty fun project!

A Distortion Bible sounds interesting but sounds like a major undertaking. Then again, I suppose most pedals are variants of other designs.


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## mhammer (Nov 30, 2007)

It would have likely included sections on the psychoacoustics and evolutionary influences on the perception of distortion (he's the engineer, I'm the psychologist), the different categories of distortion, a comprehensive whole-of-signal-path approach to distortion, what is produced where and how, some circuit analysis and examples to play with, and a walk through the various "families" of distortion circuits. At least that was the original plan. Were we to ever get back to it, I suspect it would need to have a chapter on deliberate production of distortion by digital devices, and maybe some of the unintentional stuff too. I figure we were looking at a couple of hundred pages, copious illustrations included. The goal was to simply make people smarter and more strategic in their use of distortion.


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## LydianGuitars (Apr 18, 2013)

If you want to increase bass, I'd look at changing where the pot engages on the shaft first. Its the easiest way to change the wah's voicing.


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## TWRC (Apr 22, 2011)

Yes, I have set the pot up to start sweeping from it's lowest point. It's still missing that low end bass - at least the resistor swap is reversable.


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## mhammer (Nov 30, 2007)

LydianGuitars said:


> If you want to increase bass, I'd look at changing where the pot engages on the shaft first. Its the easiest way to change the wah's voicing.


Works up to a point. You want to avoid having the gear engaging the pot too close to the extreme ends of rotation, or else you risk breaking the pot. As long as one leaves a margin of safety, though, it is the way to go and probably one of the easiest pedal mods around.


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## fraser (Feb 24, 2007)

TWRC said:


> That's the thing I hate about wahs. Some of them are really thin and "porn"-like. I really like the vocal quality of the Colorsound wahs etc, but the pricetag isn't all that great.
> 
> I had every intention on playing around with the inductor on my Vox, but never got around to it due to having to compensate other component values has you stated - so I just stuck with it. However, a wind your own Halo inductor kit sounds like a pretty fun project!
> 
> A Distortion Bible sounds interesting but sounds like a major undertaking. Then again, I suppose most pedals are variants of other designs.


i recently took one of my dunlop crybaby's and swapped the transistors and a few resistors-
matching it to the old clyde mccoy specs.
it originally had some high gain trannies- mpsa18
i used a bc109(hfe 283)
and a 2n2222a(hfe 220)

teese said that replacing the .22 cap off the wiper of the pot to .33 would mimic the icar taper, so i did that.
i replaced the other .22 and .01 caps with some better quality ones while i was at it.
the difference is astonishing.
instant hendrix 'up from the skies'.
cost maybe $5 in parts, and it was a lot of fun hearing the differences each component change made.
had my head buried in that thing for like 3 days lol.


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## TWRC (Apr 22, 2011)

I made a couple of resistor swaps last night that I need to spend more time with - but so far I'm loving it!

I swapped the resistor parallel to the inductor from a 33k to a 68k (vocal mod) and the wah sounded a lot fuller to me. I also did the gain mod and swapped the 68k input resistor with a 47k which made a very subtle difference in volume. From that point, I tried swapping the gain resistor from a 470r to a 330r as most people seem to suggest, but it just made the wah sound muddy to me. I then tried a 400r resistor and got the bass that I wanted, but again the pedal sounded really muddy in the heel position, so I put the 470r back in.

I was hoping to add a bit more gain and bass to the wah with that resistor and because I was using the stock 470r, I decided to lower the value of the input resistor just to see what would happen. I ended up using a 33k and BAM, the wah had that certain growl that I was looking for. 

The tone reminded me of this (and I couldn't be happier):

[video=youtube;qSIS0o7vtPE]http://www.youtube.com/watch?v=qSIS0o7vtPE[/video]


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## fraser (Feb 24, 2007)

fun isnt it?
i went with the full 100k at the inductor (from 33k)
i tried 68k- but when i tried the 100k i loved it.
the 1.5k between the input and the .01 cap affects the mids- i went 2.2k there
my wah actually had a 390r- i swapped that for a 470r.
i have another stock gcb-95 here.
thinking of going all maestro boomerang on that one lol.


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## TWRC (Apr 22, 2011)

It's totally fun. I'm having a lot more fun with this wah than any other one I've ever used.

So you swapped a 390r for a 470r? Just curious as to what your reasoning behind that was?


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## fraser (Feb 24, 2007)

TWRC said:


> It's totally fun. I'm having a lot more fun with this wah than any other one I've ever used.
> 
> So you swapped a 390r for a 470r? Just curious as to what your reasoning behind that was?


well, this newer crybaby used very high gain trannies-
the assumption is that many of the resistor changes are to compensate for that-
even if that assumption is incorrect,
my goal was to get as close to the sound of the old clyde mccoy as possible.
so in addition to the low gain trannies, i was matching the original values-
i only deviated in that 1.5k resistor as it sounded better with 2.2 to my ears.
essentially i traded off bass for an increase in mids.
to be honest i never played around with that emitter resistor,
i simply put the 470r as it was the stock value-


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## TWRC (Apr 22, 2011)

That makes sense to me. I'm actually quite happy with the mids on this wah. They just sit right for me and I can see it being pretty usefull in certain solo passages.

The stock 5117 trannies (which I believe are just Thomas Organ 2N2925's) are considered low gain, so maybe you're onto something here. Basically the sound that I have in my head is a Clyde with a bit more quack and bass.

I think what I might play around with tonight is bumping the input resistor from 33k to a 56k and lower the gain resistor to maybe 330r or 400r. I'll report the results later on.


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## TWRC (Apr 22, 2011)

Tonight I swapped out the input resistor that was originally at 68k to 33k and then up to 56k. 68k didn't feel like enough as when I would engage the pedal, there was a slight drop in volume that I would suspect was due to the true bypass mod. The growl that I encountered with the 33k resistor was great, but at certain toe down movements, there was some slight distortion as this swap definitely gave the wah quite a bit of boost. I eventually settled on the 56k (could have gone 47k as well as I didn't notice a huge difference between the two) because it seem to provide unity when engaged and had no distortion or artifacts when engaged. 

Due to the input resistor being raised to 56k, I was able to lower the gain resistor from 470r to 330r without the wah getting muddy as it did the night before. The wah actually gained the amount of bass that I was hoping for with a slight bump in volume. With my fuzz pedals plugged in, I noticed a lot more "wah" emphasis than I did previously. The heel down parts were nice and thick and the toe down parts were a little more mellow, but still had that bite.

I must say that I'm happy with these resistor values now - so much that I actually couldn't stop playing the darn thing. The true test will be tomorrow when I can dime my rig and play it the way I intend to play it.


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## fraser (Feb 24, 2007)

> The true test will be tomorrow when I can dime my rig and play it the way I intend to play it.


at the beginning of this thread you said you never was a huge wah user-
im the same.
but now im using it all the time.
my set up is only a pair of 5 watt amps,
18 inches of speaker between them.
a wah and a fuzzface-
but check this out.
lately the woman im living with has gotten into the habit
of handing me my guitar and telling me to play-
at 3 am.
every knob dimed and suddenly im the captain of a spaceship.
a fucking spaceship.


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## TWRC (Apr 22, 2011)

I tried the wah this morning and I think I'm done with the mods. I buttoned it up and put it on my pedalboard. 

I'm not a huge wah user at all, but then again the wah tone that I always had in my head was never a reality until I picked this one up. I guess I was always after a more vintage sound rather than the darker modern type of sound.

You're a lucky man! HAHA


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## TWRC (Apr 22, 2011)

I was at my local electronics shop this afternoon for something totally unrelated and picked up a 100K trimpot to mess around with in place of the inductor resistor. Before I soldered it in, I labeled it with some marks for 33K, 51K (which apparently some guys swear by over at TDPRI) and 68K. After playing around with the wah, it turns out that I actually prefer the "Q" at around 47K. The wah overall sounds a bit warmer, and doesn't have as much quack and bite at the top end. 

Needless to say, I wish I had installed this trimpot sooner as it would have saved me a bit of time in the soldering department earlier.


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