Duovox Wah/Volume to Wah only conversion help needed.

[Nocaster Cat]

Hey everybody...first time poster, long time lurker.

I've got a Duovox Wah/Volume pedal that I'm trying to convert to wah only and I've hit a dead end, I'm having trouble defeating the volume feature. I have searched for schematics but came up empty handed and was hoping for some input. If there's any missing info I can fill in please let me know and thanks in advance.

[Nocaster Cat]

Preliminary schematic (missing two resistors) but it looks like the Duovox is pretty much the same as a Maestro Boomerang/Boomer wah/volume.

[slacker]

I think when the switch connected to the 5uF cap is closed it's in wah mode and when it's open it's in volume mode. So to make it into just a wah connect the 2 points marked "To Switch" together.

Welcome to the forum

[Nocaster Cat]

I think when the switch connected to the 5uF cap is closed it's in wah mode and when it's open it's in volume mode. So to make it into just a wah connect the 2 points marked "To Switch" together.

Welcome to the forum

Thanks for the welcome and the reply. Unfortunately I'm not 100% sure the Duovox follows the same switching scheme as the Maestro (whcih is where I snagged and relabled the schematic from) but I'll try starting there.

[Dan N]

Can we see a track side photo, please? I'm having problems matching the x-ray to your schematic.

I suspect a volume/wah has to make concessions trying to be two things instead of just one. O.K. volume and O.K. wah. Not great anything?

[joegagan]

the bg2 boomerangs i have repaired are terrible volume pedals. in volume mode, the tonesuck is palpable, even in the presence of buffers up or down the line.

as wahs, they are wonderful. just ask  p marossy.

[joegagan]

the similarities to the boomerang are evident. what is surprising is the 2.2 uf caps where a crybaby would have .22. how does this thing sound as a wah?

the switching arrangement is the same as the maestro.

there are numerous component value differences to a boomerang 2 but the baisc architecture is intact.

[joegagan]

update. the duovox board is identical to the dearmond 1800 wah board, which i have acquired since the last post on this thread. the missing resistors nocastercat referred to in his schem are bias resistors base to ground  Q1 is 100k Q2 is 820k. these are not present in the boomerang.

[ayayay!]

I'd assume that cap on the bottom is .015uF?

[Paul Marossy]

the bg2 boomerangs i have repaired are terrible volume pedals. in volume mode, the tonesuck is palpable, even in the presence of buffers up or down the line.

as wahs, they are wonderful. just ask  p marossy.

Yeah, not the best volume pedals those BG-2s. But I don't think there is such a thing as a good wah-volume pedal. Both types of circuits really want different things. It's a compromise at best. I do think they are the best sounding wah pedals, though, which I seem to be known for around here!  

update. the duovox board is identical to the dearmond 1800 wah board, which i have acquired since the last post on this thread.

Interesting. I've never even heard of the duovox wah before.  

[joegagan]

ayayayayayay, you are correct, would be .015. if you notice in the photo the sweep cap is green in the dearmond and  ceram in the duovox. my  dearmond had a .01.

paul, i have come to the same conclusion as you have- it is damn hard to get a  volume pedal dialed in as a standalone let alone making the pot adjust correctly for 2 purposes.
in my ever-growing fantasy list of pedals i would someday like to desing and produce i would make a  wah - volume that had two pots on one axle with a dpdt to actually fully switch between two pots. then, in my dream aron nelson comes in and tells me i could do the volume function digitally and i wake up covered in sweat...

interesting before and after on my dearmond. i found it pleasing but a little boring so one sunday this past may gus smalley advised me and we did a long distance mod session where he suggested things and i tried them. the following two vids are a before the mods and after the mods expose'
stock:

mod with the assist from gus smalley:

[joegagan]

[Paul Marossy]

paul, i have come to the same conclusion as you have- it is damn hard to get a  volume pedal dialed in as a standalone let alone making the pot adjust correctly for 2 purposes.
in my ever-growing fantasy list of pedals i would someday like to desing and produce i would make a  wah - volume that had two pots on one axle with a dpdt to actually fully switch between two pots. then, in my dream aron nelson comes in and tells me i could do the volume function digitally and i wake up covered in sweat...

Ha ha, you have weird dreams! I agree, at best it's a compromise. Your idea of two independent pots is interesting. Then you run into problems with the travel available, but it could be an improvement having a passive volume pedal and a wah in one. But honestly, I never ever use the volume part of the BG-1s. I prefer the DOD FX-17 for a volume pedal (I NEVER use the wah section) - it has no pot to wear out.  

[joegagan]

i had a fx17, i recall it compared quite well to bypassed signal . is this true with yours , paul?-

i used it live before my serious pedal modding days, but i did take it apart to see how it worked and replace a switch in the mid 90s. the capacitor strip printed on mylar or whatever the clear sheet is is pretty brilliant. or is it a dark/light LED setup, i forget.

[joegagan]

if anyone is curious what changes caused the latter , 'modded ' dearmond sound fuller and better ( opinion ), here are the  shop notes written just after the mod session.
here is how i set about a mod:

1.  look up schem on internet. grab pencil and a clean sheet of paper and hand draw it. i feel this lets me think through the circuit and grok it really well before  putting solder to parts.
2. i keep notes on paper on the schematic as to the modding process but as the ear testing and parts swapping gets hot and heavy i get less careful about writing down every single component tested. some of the changes must be dbl checked before committing to notes, the accuracy as to final values is consistent,accurate.

i recommend doing this for any mod so that you create a long term library of shop notes. i have found it very easy to do by a quick types descrip( similar to a doctor makring up your medical chart very quickly) in gmail, it autosaves every 44 seconds or less , saved forever in the ether almost as soon as it is typed.

ok, back to your regularly scheduled publication of the mod notes , dearmond 1880 mod called 'mystery wah' above.

mod notes:

the hotpotz1 with 33k limiting resistor had a very annoying glitch in the sweep, like a click where it suddenly went full treble. did not matter  whether the limiting resitor was in or out, or changed  to a different R. i think the taper of the o hot potz1 when run backwards as  just way too abrupt, and no amount of messing with the 47k voice resistor across the inductor, or mispairing the 2.2 uf caps across the pot, you can smooth it a tiny bit  but not near enough. the only thing i didn't try was altering the 1k resistor off base Q1, but i am pretty sure that would not work either based on past experiments.

mods: (6 .6 2011)

went back to a 25 k audio pot with no limiting r. ebay had some mil spec NOS '70s CTS made pots 25k audio, with a clickswitch installed ( no prob in this app), i had a few laying around. the sweep is now very gradual and workable.

changed the 810 R to ground off base Q2 to 1 meg.

installed a 100k trimpot in place of 47k r across ind. ended up around 39k sounding good.

installed a 25ktrim  + 8.6K R in place of the 33k to ground off emitter Q2. sounds better at around 15-20k.


the q cap is now .02 total as i added a second .01 ceramic in parallel to the existing .01.


played around with more cap to ground at inductor. for some reason in this circ, did not notice any improvement  , went all the to 10 uf but went back to stock, no improvement.

my usual treble bleed across input R , .0022 silver mica - adds high end sweetness, makes the harmonics more lively across the freq range. makes the whole wah range wider as the treble at toe down is  increased. this works especially well with the wide foot travel of the dearmond case - if the treble is too much, you just don't press down that far, very expressive, very easy.

[Paul Marossy]

i had a fx17, i recall it compared quite well to bypassed signal . is this true with yours , paul?-

i used it live before my serious pedal modding days, but i did take it apart to see how it worked and replace a switch in the mid 90s. the capacitor strip printed on mylar or whatever the clear sheet is is pretty brilliant. or is it a dark/light LED setup, i forget.

Yeah, it's pretty transparent as a volume pedal. I also think the whole design is ingenious. It's not an LDR thing, it's something completely different. Uses an OTA an stuff. There's a schematic of it at my website.