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that brings up an advantage for the LED/ LDR setup. you could keep trimming the shutter piece to make whatever taper you want. make the shutter piece screw in and out with a simple flat bracket so you can swap them quickly. make the shutter out of thin black plastic , like from office supply file dividers etc.

for a volume pedal, the big problem is the physical limitation of the standard rack gear/round gear setup.
pots don't go full silent until they are riding right into the internal stop. this puts a strain on the pot and is very hard to dial in perfectly. also, if the same pot is used for wah , the adjustment for optimal wah may or may not be full heel down. see note 'a' below.
passive volume pedals are 250k, 500k, 1 meg, actually for most setups 500k and 1 meg are optimal. this may or may not work well with your wah.

most people expect a volume pedal to go full silent because the ernie ball and morley pedals do that. the ernie ball does not strain the pot because the string takes up a tiny bit of the strain.

some notes:
a. you could use two pots on one gear facing each other as in the old crybaby stereo fuzz wah, this way each pot can be individually tuned for optimum setting. difficult but possible. again, the volume pedal side's internal stop issue remains.
*you could rig up some sort of switch to ground out the volume pot at near-silent, see video below.

b. if you make the volume pedal active and are trying to use the same pot for wah & vol, you can set it up for a wider ( lower value) range of pots. you can also tune the circ to sound or sweep differently.

c. the maestro boomerang is the best i have heard of the old style inductor wah/ volume combos. when set up right and the proper pot is used the volume function has a nice sweep and a very mild boost at toe down. BUt, it does not go full silent on heel down.

d. pot taper. people who use volume pedals regularly are usually VERY picky about taper. it is unlikely that a pot that has a good taper for wah will be a pleasing taper for volume.

e. a dual gang pot solves the dual value problem, but suffers the 'not silent at heel down' problem in most cases.

f. the one pot solution is tricky, the two pots facing each other solution is a mechanical challenge.

g. you could rig up an opto type circuit for the volume portion. part morley, part crybaby.

is it any wonder that there doesn't seem to be a really satisfying inductor type wah-volume on the market?

switch for grounding volume pedal circ out at heel down - primitive version:

boomerang , demonstrating the volume pedal lack of tonesucking.

or boost, i guess q3 is a boost?

c3 and c4 are not polarized on the weener schematic. in other wahs that use polarized caps in this location the + would be toward the trans, not the pot.

so, kothoma is correct on c3 and c4, not sure about the buffer.

looks beeeyootiful! love it.

good point. i recall seeing threads about the expandora a long time ago, but i have not seen a schematic.

not familar wth opto-fets either, they sound like they would be good to explore.

good points all around. agreed , it is  tricky to emulate the sonic character of an amp, especially if the player dynamics of the inspiration amp are to be somewhat similar to the pedal ( even trickier when the amp emulated has such a complex character). the aforementioned power amp breakup issue is also to be considered.

i haven't tried any of the runoffgroove AIABs, or any clones of commercail types, but i did my own exploration into this AIAB idea back in 05. 'decade'
it has a JFET feeding a Ge trans, a dumble-inspired tone stack and a 3rd FET tage. the trimmers on the FETs allowed tuning to emulate preamp and power amp distortion, the Ge gave a round tubey flavor ( and player dynamics) that FETs alone couldn't match IMO.

pretty simple. i humbly suggest this might be a good rough starting point for a 'wreck-ish type pedal as it has really sweet player dynamics and a tone stack in a good location, fairly low parts count.
don't worry about the custom 22k dualgang, that can be omitted and more normal ways to bias and bring in subtle diode distortion ( possibly left off also ) can be used. i only did the tricky dualgang to let the pedal go from a very clean boost to a distortion monster one a single knob. it worked!

[a few fun facts, along with some conjecture:]

thanks!
i haven't been keeping track of the front logos as much, but yes, that would be the era, sort of a wave logo.
it is interesting to watch how dunlop progressed after they bought the crybaby brand.
a few fun facts, along with some conjecture:

in '81, jim dunlop bought the company from whirlpool. whirlpool had acquired thomas organ in a stock purchase of warwick electronics ( owner of thomas organ ) in 1966. who knew that all those crybabies we used from the 60s and 70s were essentially whirlpool appliances?

for the first few years, the dunlop crybabies were built from leftover thomas parts, best of which were the 03 inductors. previously, the majority of crybabies had TDKs with a random smattering of 03 inductors. for this 80s period, every crybaby had an 03 inductor. even the PCB was the thomas part. the first real change was the logo plate on the front. initially, dunlop was smart, they left the supplier chain intact, evidence suggests that subcontractors of thomas became suppliers to dunlop.

changes showed up as the board was redesigned to use the terminal clip wiring harness. these boards say JD DUNLOP on them and possibly made by the same company that made the thomas boards.

next set of changes were the worst era of crybabies in history. dunlop enacted cost cutting that nearly ruined the reputation of the venerable crybaby forever. features included: crappy caps, horrible inductor ( small black cylinder , 3/8" diameter,  half inch tall), crappy plastic frame jacks, etc etc.  this era saw the first dunlop branded hotpotz1 clarostat pot. supposedly rated for one million cycles ( a joke ), the cost cutting also included a short shaft and bushing, later changed to a longer shaft and bushing in around '92. it should be noted that dunlop stayed with the same basic pot supplier that thomas had used, clarostat had bought the potentiometer division of allen bradley. dunlop retained the same pot taper of the long standing crybaby specification. there was also a brief period where they used a bourns-made cermet (i think) pot. these are a small blue square body and have horrible durability.

slightly later, this era saw the introduction of the 1/8" power supply jack, while the earlier version of this crappy board did not have the power jack. the enclosure now had new longer reinforced areas where a future power jack would be added.

also during this era, dunlop dabbled in inductor suppliers. for a while they even used the same inductor as morley, and the board design was changed to accommodate the super wide pin spacing of it, while including multi-pinouts for various inductors. board quality at this point was at a low as well. thin boards with thin traces and small pads, a shift from the quality of the thomas style boards.

the one-piece 'rev E' board with the now famous layout came in the early 90s, and signalled the long road back to wah quality. better inductors were used, leading to the n30 version of the small toroid, which possibly was a result of the dunlop agreement to build the budda wahs since the budda company ( reportedly ) preferred the n30 magnet material. these n30 inductors show up in non-budda dunlop wahs, and i suspect that it is possible that all inductors of the mid 90s may have been made with this material , while some are not marked as such. just a theory. also during this early REV E period , the board quality was spotty, it seems they were experimenting with various suppliers.

the decision in REV E  to add a buffer and leave the wah non-tru-bypass is interesting. is this telling me that all the components and complexity of a third transistor stage is cheaper than the added cost of a dpdt vs a spdt and one added wire? i guess so. they may have actually liked the buffer as a way to add consistency to the sound of the wah , allowing looser tolerances in parts while still getting a 'passable' wah tone. the buffer does 'level the playing field' so to speak.

don't forget, dunlop also made the vox wahs for 25  years or so, ending around 5 to 7 years ago. dunlop-made vox wahs retained the old 2 trans, non-buffered circuit for much longer, eventually giving way to using the same 3trans board of the gcb95.

rev f, g, and h all were small refinements to the rev E formula. mid 90s saw the introduction of the hotpotz2, a very durable wah pot for the first time in history. same taper as hotpotz1, but usually a slightly lower overall value , avg 96k vs a little over 100k for the hotpotz1. hotpotz2 has plastic element, and several vintage wah experts have reported liking the actual sound of the old carbon trace hotpotz1 better. for a while, mid-90s, hotpotz1 and 2 seem to have been used concurrently. hotpotz2s have been made in 20k , 100k, 250k ( for volume pedals) and 470k.

Rev I is the first major layout change for the dunlop wah PCB. the inductor is turned 90 degrees from the previous iterations. i have a theory that this was done to make the fasel look more 'centered' rather than sideways in the fasel versions.

of course, the many offshoots ( as far back as mid 90s) , gcb95Q, dimebag, mister crybaby super, and other versions had very complicated boards not similar to the basic gcb95 style wah. however, even some of the recent signature wahs have the gcb95 as their core.

update, i looked in my junk box, i found clear jacks as late as rev g , 94. dunlop seems to have dabbled in asian low cost board production at this point, with parts and board quality at a low that was later rectified.

this is around 91-93. clear jacks, small toroid ( later became n30 , etc). very early in the rev e board period.

probably a good sounding inductor. most likely 600 mh plus or minus 15%, 14 to 18 ohm.

this era dunlop wahs are actually quite good sounding, stock. hotpotz1 pot with glued on gear, probably.

i dig the deep sound of that clip octa!

did a little boomerang makeoveri call 'rusty mustard". on its way to canada as we speak!

jeff, super looking wah!

how about a gutshot of the wah, since you have one of the few red devil inductors outside of my custom builds. my new version looks like this:

i have several theories about what makes a real analog inductor wah sound and feel so special.

the simple analog path is one,

the taper of the pot and how it charges and discharges the cap to ground off the inductor are another ( time factor for charge/ discharge as it relates to how the pot loads it).

pots are not all mfgr'd the same. since the pot in a wah is a divider,  the R going to either side at any point may be more or less of the sum total , lots of little variables.

the distortion in the circ is a real key to the character. very easy to manipulate in bipolar trans analog, a little trickier to simulate or modulate gracefully in more complex arrangements.

thanks guys.

ya, i need to resurrect that concept and put the dual wah into one shell. i haven't figured out the best actuation tho. would like to retain the ability to use one or the other independent as well.

i would like to try one of the EH wahs, it seems pretty cool. i always like new technology applied to pedals. someone told me the actuator inside is the same technology as the thing inside an ipad that detects position.