Wah wah pedal recommendation.

[Henry89789]

I am thinking about building a wah pedal and using a cry baby for a housing. I saw an old Grateful Dead you tube video (Sunshine Daydream, Venetta, 1972) where  Jerry Garcia was playing a Colorsound wah which sounded real good. does anyone know of a schematic for a colorsound wah, or a any other wah which sounds like that; or at least a schematic for a wah which sounds good, i.e., better than a cry baby.

[Transmogrifox]

Google is your friend:


Pretty much is a Crybaby with a few mods -- which really is most wahs.  Biggest thing I see here is it doesn't include the parallel resistor with the inductor (typical Dunlop is 33k).  This might indicate a particularly high-Q wah, or a relatively low-Q inductor in the original Colorsound wah.

This type of wah is going to rely a lot on the inductor used.   Your best bet is to do layout of the classic wah and start trying mods you find on the internet to get the sound you like.

Geofex site gives a good run-down of what does what:
http://www.geofex.com/article_folders/wahpedl/wahped.htm#basicmod

If you don't want to mess with an inductor then here's something you might be interested in trying:
Inductorless Classic Wah Emulator

One thing I didn't mention in the analysis that I have discovered later is that it would be a good idea to buffer the output because it doesn't go into a low-impedance source without losing resonance.  This means it doesn't play well in front of a classic fuzz (fuzz face-type circuit).  Output buffer would fix that situation.

[Henry89789]

Yes. Thank you. I did find that Phillip Bryant schematic all over the internet. But I was hoping that someone would tell me something more about it, which you have done, and I appreciate it. I suppose that is what you all would call a "verified" schematic? I will read the Geofex article. I have four cry baby wahs. Two of them are modified, one each, with red and yellow fasels. Another newer one is modified to make it true bypass, and another one is an unmodified very old model that does not even have an input for a 9v power adapter.  Which do you think is the best one to use to build the colorsound wah? Would you use the red or yellow fasel? How about the inductor on that old crybaby? Look at Jerry Garcia playing the Colorsound wah at 1:15:03 in this you tube video. The treadle on the colorsound seems to have a much greater sweep than a cry baby. How will that affect a colorsound circuit inside a crybaby housing? Oh, another thing; I have built a Klon buffer and a TL071 buffer; would either of those work for the output buffer that you suggested be used? Thanks for any additional info you can provide. 

[Henry89789]

Here are the pics of the old crybaby and the newer one. BTW: Here is another you tube video with Jerry Garcia playing the Colorsound wah at 13:56-13-59; He sure gets a beautiful tone out of it (Yes, I know: I'm no Jerry Garcia)

[slacker]

Don't forget there's also the Colorsound inductorless wah as discussed here http://www.diystompboxes.com/smfforum/index.php?topic=44348.0 these sound very different to Cry Baby style wahs. I've got no idea if Gerry might have ever played one though.

[PRR]

Don't forget that the Dead and their crew were very High-Tech in their day, making a lot of their own gear and modifying the rest. Jerry's pedals may have been far from "stock".

[Transmogrifox]

You can use any one of your Crybaby units to get the sound you want.  It's just a matter of removing a resistor, replacing one with a short, and changing the value of another.  Then there's also the question of the treadle -- you might need to advance it or move it back a notch -- might even need to replace the pot with a different taper or something.  If you want to do an exact conversion to the Colorsound then you will need to find out what pot taper they used and what range of the pot was actually turned by the treadle (my GCB95 crybaby uses the full range from almost nil up to 100k but I have heard of other wahs not using the full range of rotation).

The extended range is due to the nonexistent resistor in the emitter of the first transistor stage. 

Thinking back to RG's article in Geofex, he points out how the negative feedback is used to emulate a variable capacitor.  As the loop gain increases, the effective capacitance decreases, and so the wah filter resonant frequency goes higher.  If you increase the gain you increase the range.

The loop gain in a typical dunlop or vox wah is limited by a resistor in the emitter:
Look at R4 in this schematic.

When I mention the inductor making a difference I'm not talking about some "magic" between a red fasel or a yellow fasel or some run-of-the-mill telecom transformer.  If you want to match the Colorsound you may have to find out what inductor was used.  The main parameters of interest are
(1) What was its real inductance -- the schematic shows "500 mH", but who knows what they used during production.  Could have been anything between 400 and 600.
(2) "Q" factor of the inductor:  What is its series resistance, parallel capacitance and core losses?  They may have used a lower Q inductor and found they needed to remove R7 from this design.

#1 you can compensate by changing the value of the 10nF feedback capacitor.
#2 you can compensate by adding or removing resistance from your stock Crybaby inductor.

You may be able to get the same sound you're looking for just by messing with the equivalent of R7 and R4 in your existing Crybaby.

[Quackzed]

the last pic must be your old 'pre power jack' wah. thats the mojo 'stack of dimes' inductor' i'd leave that one alone. I know you'll hear that theres no mojo to these and that they made TONS of 'em but i'd leave it alone as far as modding. they ARE good sounding inductors. and worth a little $ ,not a lot but they are a collectible vintagey thing so i'd leave it alone and take care of it. i've got a few thomas organ wahs with the '03' stack of dimes inductor. i like 'em over the others, mellower maybee is the word... but i enjoy their history and so i take good care of 'em. 

[Henry89789]

Transmogrifox:  Thanks for your reply and the schematic links. I think I will take your advice and change the R7 and R4 in my newer Cry Baby. Do you have any suggestions as to what I should change them to? The Vox V847 schematics you linked to shows R4 as 510 ohms, and R7 as 33k; I suppose I should start by trying 510 ohms for R4, and 33k for R7. Other than those, what values would you try  in R7 and R4? How about the 10nf capacitor; What would you change that to?

Quackzed: Thanks for the reply. I will take your advice and leave that old 'stack of dimes' inductor Cry Baby alone. It is not true bypass, and it does sound good, but I can tell the difference in tone when it is switched off. But I understand that if I put a buffer in front of it, then there will be no 'tone suck.' Do I understand that right? Anyway I built a klon buffer and a TL071 buffer; so I will try those in front of it to see if it makes a difference.

slacker: If you go to the times that I put in my posts regarding the Grateful Dead videos, you can see what Jerry is playing. In the Sunshine Daydream video they actually zoom in on the wah. It is a black colorsound with a chrome treadle. In the Beat Club video, you can tell it is the same pedal.

[Transmogrifox]

First thing is match part values to Colorsound and then go from there.

That means R3 replaced with short circuit (wire) and R7 removed from the board.  Input resistor changes to 100k in Colorsound.

Listen to the sound of that and report back. 

[Quackzed]

i believe jerry used the colorsound wah/vol pedal, don't want to further  muddy the waters, but there are a few slight differences between the 2 schematics ,even when ignoring the vol switched side, note c5 etc... not sure if this is the correct shem, or if the wah/swell and vol + wah are in fact different, just figured i'd mention this in case for future reference. if you decide your build isn't quite where you want it, this might be helpful to compare to... looks like it's swiched to the wah side in the schem...

[Henry89789]

Transmogrifox:

I think that the mistake that I made (which resulted in the pedal not working) was that I changed the R4 and R7 on the crybaby board the way you said that R4 and R7 should be changed, but I think that the R4 and R7 that you are talking about are not the same as the ones on the Crybaby board. You said, "You may be able to get the same sound you're looking for just by messing with the equivalent of R7 and R4 in your existing Crybaby." I missed the significance of the word "equivalents" in your post. The R4 on the CB board is  22k, and the R7 is 470k; so I think that these are not the "equivalents" of the CB R4 and R7. So the question is:   What are the "equivalents" on the Crybaby board to the R4 and R7 on the Vox schematic you attached? Is the R4 on the Vox board actually the R9 on the CB board? And is the R7 on the Vox board actually the R5 (the only 33k resistor) on the CB board? 

[LightSoundGeometry]

http://www.electrosmash.com/crybaby-gcb-95

http://www.electrosmash.com/vox-v847-analysis

[Transmogrifox]

When I said "Equvalent" I was referring specifically to the schematic I linked for the VOX wah.  What I meant is that the resistors in the same position as R4 and R7 noted in a Vox schematic should be changed, with the implication that the Vox wah is very similar to the crybaby, BUT the resistors from a Vox wah will be numbered differently in your Crybaby. 

I was assuming you would take the time to figure out which resistors these are in your Crybaby.  Didn't even cross my mind that you might just replace "R4" and "R7" as if a Vox wah PCB numbering scheme translates 1:1 to a Crybaby.

[Henry89789]

Lightsoundgeometery: Thanks for the links. The numbers on Crybaby circuit analysis don't correspond to the numbers on the Rev. G circuit board in my Crybaby, although they do correspond to the numbers on the Vox 847 circuit analysis. But I think I got it figured out now.

[Henry89789]

I decided to just buy a Colorsound wah; Found a relatively good deal on Wah-swell Colorsound on  E-bay. I thought you guys would like to see it ...; ;;http://i1126.photobucket.com/albums/l603/henry7895/20160902_175827.jpghttp://i1126.photobucket.com/albums/l603/henry7895/20160902_175847.jpg[/img].

The housing looks pretty cheaply constructed; the bottom has to be pried off, but the inside and the cam look in very good condition. It sounds pretty good, but it seems to work in a reverse way from the Crybaby; it wahs and gets the gain with the treadle going up, instead of going down. Is that the way the Colorsound wah-swell is supposed to work? Or has someone messed with it along the way? Also if I were going to rig it up with a battery snap adapter would this use a center negative power supply like the crybaby (and all the other pedals I've ever seen)?