Foxx Guitar Synth Wah

[Mark Hammer]

The loop may not be working well for you because  of what isn't in front of Z2-2.  Seems pretty sparse to me.  You probably want an RC network in there.  Alternatively, take a look at the Colorsound Vocalizer and the EHX Talking pedal.  Note that they feed the input to a clean gain stage and a diode clipping op-amp stage, with their respective outputs fed to the outside lugs of a panpot.  That permits for continuous variation of how much harmonic emphasis you want to add.
http://www.freeinfosociety.com/media/pdf/4101.pdf

[digi2t]

The loop may not be working well for you because  of what isn't in front of Z2-2.  Seems pretty sparse to me.  You probably want an RC network in there.  Alternatively, take a look at the Colorsound Vocalizer and the EHX Talking pedal.  Note that they feed the input to a clean gain stage and a diode clipping op-amp stage, with their respective outputs fed to the outside lugs of a panpot.  That permits for continuous variation of how much harmonic emphasis you want to add.
http://www.freeinfosociety.com/media/pdf/4101.pdf

Hi Mark,

First off, best wishes to you and your family this holiday season. All the very best.

My first time around with the loop wasn't so great, because I wasn't injecting the return into the right spot. As you mentioned earlier, I should have simply interupted the path where the 4.7K resistor is, this worked much better. Rather, I simply copy/pasted the circuit from the Meat-sphere, and incorrectly returned to the inverting input of the op-amp. I really would like to stick to the loop idea, leaving the pedal open for "outside influences".

As for an RC network, I don't have any experience in the concept, so I guess I'm going to have to get up to speed on that as well. If you have the time to give me some of your wisdom, I'd appreciate it. In the meantime, I'm hitting the net on this one. More to learn.... yyyaaaaaaaaa  

As for the vero, I found a bunch of errors, due to the fact that I managed to find a bum pinout diagram of the TL074. That sucker lead me completely astray, . Thanks to Ian for initially pointing out the tip of the iceberg. Owe you one brother.

I adjusted the vero to the correct pinouts, tweaked some switch numbers, plus added some other stuff that was missing (filter cap, and pot). Posting it for verification purposes only. I'm going to trace it again tomorrow.... very carefully (it's personal now!). I also updated the schematic to add the filter cap.





Off to bed now...

[digi2t]

OK, one tiny error with R21, but it's corrected now. All the pinouts line up, as does the rest of the circuit. I'm comfortable enough now to go to vero.

I made sure to throw out that damn stupid pinout abortion that I printed the other day  . That taught me to verify, verify, verify.

Mark, if you'd like me to try something funky here (well... not TOO funky) with the loop, let me know. I don't mind being the guinea pig  . Going to read up on RC networks today.

[Mark Hammer]

One of the better uses of such a loop is filtering a synthesized octave-down.  Because those tend to be finicky with respect to triggering, and also tend to provide a rather non-dynamic signal, it is usually best to extract an envelope before feeding one.  Of course, because they generally produce square-wave outputs, they provide a nice harmonically rich signal for filtering.  Sticking something like a Blue=Box, or similar, in the loop is a natural combinations, liked pie and ice cream.

[digi2t]

Just wondering out loud here...

Would a VTL5C3/2 work here? Use the center (common) pin of the LDR side to connect to pins 7 and 8 of the IC. Then one leg to 9 (one LDR), and the other to 13 (the other LDR)?

Hmmm, I have some. Time to try it while it's still on the breadboard 

[Ronan]

I went over the latest vero revision, just a minor error, D1 and D2 appear to have the band at the wrong end. All else looks fine.

On the shematic, C10 on the MAX1044 shows reverse polarity, and the option for T2/VR2 shows a short circuit from 9V to ground.

I think you got it pretty well nailed now Dino

[digi2t]

I went over the latest vero revision, just a minor error, D1 and D2 appear to have the band at the wrong end. All else looks fine.

On the shematic, C10 on the MAX1044 shows reverse polarity, and the option for T2/VR2 shows a short circuit from 9V to ground.

I think you got it pretty well nailed now Dino

D1 and D2 fixed. C10 was backwards on both, corrected. T2 corrected as well.

I don't know why this sucker has been so problematic. To much X-mas cheer maybe  .

Please... don't drink and draw.

Thank you sir.

[digi2t]

Just wondering out loud here...

Would a VTL5C3/2 work here? Use the center (common) pin of the LDR side to connect to pins 7 and 8 of the IC. Then one leg to 9 (one LDR), and the other to 13 (the other LDR)?

Hmmm, I have some. Time to try it while it's still on the breadboard 

OK... I went, I tried, I got my ass kicked. It doesn't work. Guess I'll try doing the custom Vactrol job.

[digi2t]

Here's a video of the custom Vactrol results. the build report for the Vactrol are here; http://www.diystompboxes.com/smfforum/index.php?topic=95269.0

This baby will be going into the build, rather than the twin VTL's. It sounds better, and is cheaper than the VTL's. The dynamics are much better, especially in BP, and LP mode. I was never completely happy with the LP mode, thinking it a bit muddy for my liking. Much cleaner now.

One note though, the 25K trimmer for tuning the range, had to be changed to a 500K. This Vactrol is running around 116K for the LED, whereas the twin Vactrols were down around 19K. You can use a 250K as well, but I didn't have any, so a 500K was pressed into duty. I retained the 270 Ohm resistor as the backup to ground.

Thanks to Ian for pointing me towards the LDR's. They were meant for the Talking Pedal, but work beautifully here as well. The LED is a 5mm clear bright white, available at Mammoth Electronics.

Thanks also to R.G. for his recommendation of black gelcoat tint, mixed with the 5 minute epoxy, to cap the ends of the tube after everything is set. Sheer brilliance. 

[digi2t]

I've reworked the drawings to accomodate anyone who wishes to roll their own Vactrol like mine. The nice part with the custom Vactrol is that it takes up less room on the vero, thus reducing the footprint. The vero should fit both ways into a Crybaby now. I've also included an updated schematic, that reflects the vero.





This is the layout I'll be using to verify the build.

If anyone is going with the dual VTL5C3 build, please let me know how it works out, so I may stamp a verified on it.

[pinkjimiphoton]

gonna be a while bro, but eventually i wanna build it!

great job all around, keep it up, and happy new years my brother!!

[digi2t]

Thanks bro. Here's a pic of the board just about populated. I'm missing the 220K resistors, they're in the mail  



The off board wiring is gonna be real spagetti  .

[digi2t]

Yeeee Haaaw, it works!!!

I discovered two small errors, which I corrected on the vero and the schematic, and are reflected above. They tuckered out my troubleshooting hamster today, but perseverance prevailed. I've marked them as verified as well. I'll be uploading the updated versions to the gallery as well.

Video will be posted tomorrow.

[joegagan]

this thread is awesome. my first time delving into it. dino , you are a legend in the making.

[digi2t]

this thread is awesome. my first time delving into it. dino , you are a legend in the making.

Thanks Joe! I'm very honored by your praise, since there are a bunch of you "pedal Jedi's" that I look up to, you among them. Thanks for throwing another shovel of coal into my fire.

Well, as promised, pics and and a vid.

I was lucky to come across this behemoth, the EXR Projector. It was marketed back in the 80's as a sort of "aural enhancer". In reality, was a fancy volume pedal, really crap weak wah ,slash paper weight. The latter, being it's best trait. But, casing wise, this thing is hoooooge, dwarfing a Crybaby. Also, it's SOLID cast aluminium, I mean heavy. No... I mean cave-somebodies-skull-in heavy. Keep this baby next to the night table, in case of a home invasion. You can subdue the perp, and in a pinch, this baby will take a bullet or two. Anywho, for a real "switch n' knob" monster like this project... perfect! I was lucky enough to find two, here is an unmolested one, next to a Crybaby, for size reference.



I proceeded to gut the casing, but since the switches, and pedal were PCB mounted, I decided to keep the parts of the boards that I would require to use for the Muttroxx. The real bonus was that there was a fourth switch, hidden inside. Since the original pedal ran on 120vac, the hidden switch served to switch the tranny over to 220vac if required. Lucky again, I could flip the switch around, drill a hole in the casing, and viola!, I have my UP/DOWN switch. There is also a segmented LED section, which on the original served as an output level meter. I used this as well, blacking out alternating LED's, and now it's a filter selection indicator. 3 green LED's for the pass filters, and the last 2 yellow for the flanging. From left to right; Pedal/Envelope selector switch, Resonance pot, Hi/Lo range toggle, Output volume, Bypass switch.



On the right  side, the Wah/Speed selector switch, and the Filter selector rotary switch.



On the left side, the Envelope sensitivity pot, and the Up/Down selector switch (this was the hidden one inside). I actually had to use a counter-boring bit, to take down the thickness of the casing for the pot. I was way above the threads here. Like I said before, this thing is "built like Russian tank Comrade"!



On the front, power jack, and effects loop jacks.



Now the guts. Like I said before, I recycled the boards from the original. Mouser and Digikey still stock the exact type of switches and slider pots as well. Even the little chrome tops for the switches! Here are the part numbers, in case anyone decides to take on this adventure;

Slider pot - Mouser P/N = 312-9201F-1M
Pushbutton switches - Digikey P/N = 401-1226-ND
Chrome switch caps - Digikey P/N = EG1099-ND (These come in colors as well)  

I swapped out all the switches for new 4PDT's, and the pot had to be replaced, since the original was 10K, and this calls for a 1M. I stripped the two boards of all components, cut all the traces that may have conflicted, and chopped out a section of the main board, for access to my new board.



This is a wiring monster. Not for the faint of heart. My Mr. Multi build was good training for this sucker. Good fat harness in here brother! Unfortunately, the harness is hiding the custom vactrol I made for this project. Info on the custom vactrol construction is here; http://www.diystompboxes.com/smfforum/index.php?topic=95269.0 . The off-board wiring is taken from the schematic, since my vero layout is already pretty heavy. What I recommend before starting, is to highlight all the lines on the schematic that represents wiring. It will be easier to progress through it when you get to that point.



Here is a shot of the secondary board, which the pot, and some of the switches and LED's are mounted on.



And a close up of the pot workings. Pretty simple, just a silicone tube, in an eye hook, and the slider actuator fits snuggly into it.



Now the meat and taters. The different filter selections, along with the Hi/Lo selector give you a great range of filtering. In it's essence, this is a Mutron III ripoff, with a wah or LFO speed selection added. That's why I renamed it the Muttroxx; Half Mutron, half Foxx. A mutt! The added trimmer for balancing the Up mode against the down mode works quite well, once set up. The Envelope sensitivity can be tweaked to give you just the right WAHP (or PHAW   in down mode). Basically, one could really tweak this to get along with just about any input.

Once again, I have to thank Mark Hammer here for the effects loop idea. You can plug in your fav dirt pedal, or get crazy with a delay, whatever your heart desires. So, without further ado, the customary video. Unfortunately, I don't have the camera charisma (or chops!) of say, a pinkjimiphoton, but hey...what's a guy to do.   Gives a general overview of what the clone sounds like.

By far, one of my most complex builds, but very satisfying when things come together. I'd never fork out 1300$ for original, but I would recommend building one, if you've got a hankering for an auto-wah.  
Another step in preparation for the Ludwig Phase II clone build. I'm hoping to use the second EXR for the Ludwig.
Many thanks again to the forum, and all who helped out with info and encouragement. Rock on brothers!

Cheers,
Dino

*EDIT* - Just had to add a mod here. In Envelope mode, I was getting a high pitch whine, that I managed to trace down to the LFO section bleeding into the audio path. I then found that I would only hear it if the Pedal Mode switch was in the Speed control setting. In Wah setting, it would disappear. Looking at the diagram, I realized that the pot was going to ground in Wah mode, so it would kill the LFO whine. In this case, the Pedal/Envelope switch has to be a 3PDT (with a ground and +9 going to this switch, you can still power LED's if desired). Use the spare pole on the switch to ground pole 2 on the pot when in Envelope mode. This will kill the LFO completely, no matter what the pedal position, and eliminate any possibility of noise from the LFO section. I had already modded the original circuit by cutting the +9v to the LFO, to get rid of the ticking. Unfortunately, it wasn't until I packaged the deal that this problem popped up. Anyway, problem solved. I've updated the schematic accordingly.

Time to rest my hampster.... again  

[DiscoFreq]

I have one of those EXR's too, but I think I still have to test it (didn't have a 220v to 110v converter when it arrived a few years ago). You're right, it's VERY heavy

[digi2t]

I have one of those EXR's too, but I think I still have to test it (didn't have a 220v to 110v converter when it arrived a few years ago). You're right, it's VERY heavy

Yeah... if this pedal was a ship, then it's the USS Missouri 

[Ronan]

Excellent job there Dino! Wonderful bit of engineering gone into that "battleship".
I have a build under way today. It's going into an Aria wah shell, with a simplified user panel (read less bells and whistles), but it will have the mandatory send and return jacks for using a dirt pedal in ENV mode

here's a pic

If the jumpers on the PCB and the home-grown Vactrol look familiar, its because Dino graciously gave me a nice pre-prepared vero PCB! Thanks mate, looking forward to seeing how this turns out.

[digi2t]

Excellent job there Dino! Wonderful bit of engineering gone into that "battleship".
I have a build under way today. It's going into an Aria wah shell, with a simplified user panel (read less bells and whistles), but it will have the mandatory send and return jacks for using a dirt pedal in ENV mode

here's a pic

If the jumpers on the PCB and the home-grown Vactrol look familiar, its because Dino graciously gave me a nice pre-prepared vero PCB! Thanks mate, looking forward to seeing how this turns out.

Your very welcome friend! One good deed ALWAYS deserves another 

BTW, I noticed that you don't have the latest version of the schematic there. I've updated it since, and explained why in my edit, at the end of the build report above. Basically have to add another wire, and a switch type change, but very important to the operation. The problem didn't manifest itself on the bread board, but once you pack everything together, it bleeds into the audio. I'm very surprised that the original didn't deal with the LFO noise. Then again, maybe that's why they never made a big splash.

You may want to test that vactrol, to be sure that it's working properly. When I was making it, once I put it together, for some reason the LED failed. Luckily, the epoxy was still soft enough for me to open it up, and change it. I tested it again before I sent it to you, but if you could validate it's operation, it'll remove a little black cloud hanging over my head. It's funny, I never had a problem with mine. Guess I laid my hand on a weak LED at the time.

I've been fiddling with the trimmers mine, and I think I've got it just about to my liking. Once I'm satisfied, I'll take some readings, and pass them on to you.

[Ronan]

No worries, the vactrol is tested and working. I forgot to refresh the browser, hence the older schematic. I'm thinking of going without the LFO, so will be using the Pedal (without speed) and Envelope modes. Got a few holes to drill today...better get moving on it

Edit: a quick question, do we really need a volume pot on the outside or would an internal trimpot suffice?