Foxx Guitar Synth Wah

[digi2t]

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?

Hmmm, that all depends on your set up I guess. Since I run all my effects through a midi matrix router, it means that I can mix and match my effects chain and order any way I want. I've found that it's useful for me to have a volume on each effect for balancing when creating a particular chain. It really depends on whether your needs really require an external pot. If you're using a set order of pedals, then yes, an internal trimmer would be fine. Set it, and forget it. I would drill a hole in the cover plate though, so I could just use a trimmer driver to make an adjustment if necessary. 

Looking at the vero, you've got a spot just below the 15uF cap for the trimmer. You should be able to shoe-horn it in there.

[Ronan]

Now this is interesting, the Mutron III and the Neutron (RG's version) have one end of the sensitivity or gain pot unconnected. I think it is done like that so that the gain of the first stage is adjustable by the ratio of the 120K resistor and the variable resistance of the 1M gain pot. But the original schem of the Foxx synth wah on page one of this thread shows one end of the gain pot going to ground. Something to try.

[digi2t]

Now this is interesting, the Mutron III and the Neutron (RG's version) have one end of the sensitivity or gain pot unconnected. I think it is done like that so that the gain of the first stage is adjustable by the ratio of the 120K resistor and the variable resistance of the 1M gain pot. But the original schem of the Foxx synth wah on page one of this thread shows one end of the gain pot going to ground. Something to try.

Dude, that one completely blew by me  . I've got to look into that one as well.

There is also the difference of input caps between the two, 10uF versus 4.7uF. I did experiment here, and I found that to my ears, splitting the difference at 6.8uF was good for me. You might want to fool around with the values here as well. Season to taste  

Another place you might want to play with is the cap going into the detector, 1uF on my schematic. Between the Mutron and the Foxx diagrams, it varies between 2.2uF to 10uF. Personally, I had a bit of a hard time picking up the higher register with the 10uF. There wasn't much difference between the 1uF and 2.2uF, but I went with the 1uF, because I could just tweak the Sensitivity to zone in the detector. No biggy.

Cut the ground on the Sens. pot.... hmmm....Hang on....

OK, better with the ground off. Not that you'll ever go that low on the Gain, Sensitivity, whatever you prefer, but if you do, at least you don't lose your signal completely. Left mine disconneted, and tye-wrapped it to the harness.

One other thing I just discovered (still exploring this sucker  ), in the high range, in pedal mode, if you go into speed control mode, you get the LFO ticking coming through the audio. Only in high range. If you go to low range, it's inaudible. It reminds me a bit of the fuzz percussion on the Ludwig Phase II. It seems that I read Mark Hammer's info on using a seperate op amp for the LFO too late in the game  . Oh well, personally it doesn't really bother me because to date, I've found that I'm on the low range most of the time. Maybe for fun, I'll try an RC network on the V+ side of the chip, or I could just redraw the vero to use two dual opamps, instead of a quad here. We'll see.  

OK, tried the RC network, but no dice. Tock, tock, tock... Like I said, only in high range, and most prominant in low pass, less so in band pass, almost inaudible in high pass. In low range it's fine, in all filter ranges. Two seperate op amps should be de rigeur here, if one wishes completely tick-free operation.

*EDIT* - Been doing some reading, and came across a deticking strategy used in the Boss BF-2 flanger, again by a post by Mark Hammer, at the bottom of this thread; http://music-electronics-forum.com/t1073/ .  Man, that guy is golden! Anyway, looking at the BF-2 schematic, the strategy seems fairly easy to implement, so I'm going to try rigging this temporarily, and see if it does anything.

[Ronan]

Thanks for checking that out. I finished the PCB last night, but found some unexpected engineering challenges today with the wah shell, so I probably won't get it wired up and running until next weekend. But all is well and looking very good at this stage.

[digi2t]

Thanks for checking that out. I finished the PCB last night, but found some unexpected engineering challenges today with the wah shell, so I probably won't get it wired up and running until next weekend. But all is well and looking very good at this stage.

Is the Aria shell comparable to a Crybaby? If so, I found that the best pots for app's like this is PEC. He's a shot of my Mr. Multi clone, with a PEC pot (1M also);



Fits perfect, and is military grade. They also come with a long shaft (2" I believe) so you can cut it to length. They're a bit pricey though, at 9$ Can. a pop, but good for life though. You can order them from ABRA electronics. http://www.abra-electronics.com/categories/Potentiometers/P2W-Series%252d-2-Watt-Linear-Taper%252d-Long-Shaft/

[Ronan]

OK, that PEC pot is a good idea, I'm a bit new on wah setups, well, lots of things actually pedal-related. Abra has a large minimum foreign order, but there is one on ebay, looks good.

The Aria looks very close to the Crybaby, but I think it might be made in China and they fitted a steel L-bracket to mount the original 24mm Alpha pot, and didn't use the big lugs cast into the housing for a standard larger pot. This arrangement is a bit rough as the rack and pinion is operating a long way from the pot, causing undue stress on the bush inside the pot. Also it left me no room to mount a SPDT switch where I wanted to. I wanted to mount the new 24mm Alpha pot I bought in the large lugs, or cut the lugs out and use the angle bracket but move it closer to the rack to make room for the SPDT switch. The solution I found in my stash was in the form of a small lamp holder, which has a bezel that screws into the front of it so you can change the color of the bezel if you want. This lamp holder is like a bushing that has an internal thread and an external thread. It just happens the inside diameter and thread of the lamp housing fit the thread of the new 24mm Alpha pot I intended to use, and the outside diameter allowed the pot to fit nicely in the lugs, and the extra length allowed me to be actually able to mount the pot also, as the original threaded shaft was too short to get a nut onto it. Here's a close up shot of the arrangement.

With that sorted, and all the holes drilled, you can see I ended up with some sort of symmetry, and here's a pic from above. As you can see I went for minimal options at this stage, pedal/env, BP/LP, sens and res pots, and send and return jacks. The caps are bent over at one end of the PCB since there is not enough vertical clearance inside the housing unless I grind off some cast bosses that were used to mount the original wah PCB. I can do that at work if required, I'll just see how it goes. Now the new apprentice at work needs some soldering and wiring skills so the pedal is going to work to hopefully be completed under my watchful eye. It will be a good learning experience for him, plus he expressed an interest in all things music and especially in wiring up a pedal. Hmmm.

[digi2t]

It just happens the inside diameter and thread of the lamp housing fit the thread of the new 24mm Alpha pot I intended to use, and the outside diameter allowed the pot to fit nicely in the lugs, and the extra length allowed me to be actually able to mount the pot also, as the original threaded shaft was too short to get a nut onto it.

Wow, that looks good. I've run into that problem before, but this is the first time that I've seen those bushings. Thanks for the heads up Ian! Going to hit my hardware store today, and maybe get a few to keep handy. The lay of the land looks very nice. Great work to date. Just one tiny thing though, I've found that it's better to mount the in/out LED on the side, just below the heel. It's much more visible there, especially if the pedal is an a heel down position, and you're looking at it from an angle. At the top, below the toe, it'll tend to disappear from view at times.

As for the the PEC pot, if ever you see anything you might need on this side of the pond, PM me. We can take a look at it, and if it's financially advantageous, I don't mind picking it up for you here, and posting it to you. You can just Paypal me instead. Sometimes, the cost, shipping, and/or conditions domestically are much better. ABRA for instance, has a store about 10 minutes from where my girlfriend works  .

Again though, NICE catch on that bushing! Killer man.

[Ronan]

I got the envelope section running and tuned the caps. I Really like it! The filter works well, will try to do a sound clip later.

[digi2t]

Great news!!!

Looking forward to soundbytes. Maybe a video?   I'm happy it works.

P.S. Let me know what you settle on for caps. Just out of curiousity. Thanks.

[Ronan]

Sound clip, be warned its 6 mins long, 6 meg, 128 kb/s mp3, just noodling. If it gets boring, try 3:00 manual pedal with dirt, 4:20 manual pedal clean, 5:15 envelope clean. I used a marshall guvnor clone in the send/return for dirt. I'm using 6n8 ceramic caps in the filters, and I think the whole clip is with Low Pass selected. On this unit here, band pass will cut some bottom end and give some more top end, read "treble boost". Because I went with simple options, it turned out more complex. I left out the LFO, but then had to knock up a different voltage feed to the pedal pot to get it to work right, which it does well now. I can post that circuit later if anyone is curious.

sound clip

[digi2t]

EXCELLENT!!! Really nice. Sounds just like mine. Really helps validate the custom vactrol build as well.

It would be cool to post your circuit as well, since maybe someone would want build a stripped down version as well. I could upload it into the gallery as well, into my Muttroxx folder.

More knowledge = more power 

Really nice Ian. Have fun with it buddy!

[Ronan]

I'm just wondering if it wouldn't be easier just to put the five LFO parts in, but I can't work out what the output of the LFO opamp would be in WAH mode. I'm only using about 1.5V across the 1M wah pot. Dino, would you be able to measure the voltage at pin 1 of the LFO opamp, with the pedal in WAH mode?

[digi2t]

I'm just wondering if it wouldn't be easier just to put the five LFO parts in, but I can't work out what the output of the LFO opamp would be in WAH mode. I'm only using about 1.5V across the 1M wah pot. Dino, would you be able to measure the voltage at pin 1 of the LFO opamp, with the pedal in WAH mode?

In wah mode, I'm getting a steady 8.47vdc to ground at pin 1. My power supply voltage is 9.14vdc.

[digi2t]

I decided to add a 330K tapering resistor across the pot poles on the schematic. Like the Mr.Multi, it helps center the taper of the sweep in wah mode. Otherwise, it's too bunched up at one end. You can also use a 500K trimmer as well, for a bit more adjustment flexibility.

I've uploaded the updated schematic to the gallery, under "Dino's Stuff".

[Ronan]

I'll give that 330K resistor a go Dino, I didn't get any pedal stuff done today except for a brief blast through this one, I am really appreciating the difference between pedal sweep and envelope-driven sweep, they are more different than I would have thought, I still need to play this pedal more to learn it. I really like the seeming slow attack in env mode when not pushing the envelope very hard, like a bowed effect, you can hear that in the last few seconds of that clip I did. The other discovery was hitting a chord in pedal (wah) mode with the filter closed and slowly opening it up (with dirt running for sustain of course). This filter starts off deeper than my amp can go (read a low rumble) and then opens up into a chord or whatever I just played, very nice, I don't have anything else that can do that.

[digi2t]

This filter starts off deeper than my amp can go (read a low rumble) and then opens up into a chord or whatever I just played, very nice, I don't have anything else that can do that.

Oh yeah, it can get pretty low, all depending where you set your range. Don't forget, this is a direct cop of the Mutron III circuit, which has been used on everything from guitar, bass, keyboards, and anything in between. It's very tunable to play nice with other instruments, high or low. 

[Tony Bach]

Dear Sirs,
I have my friends Foxx Gtr Synth that does not work.  There were a few wires unhooked.  We are not sure where the one battery ground goes.  We have one battery + connected to the middle upper terminal of the on/off and the negative goes ?  We have the other battery negative connected to the middle lower terminal of the on/off and the positive goes the the pin 2 of the circuit board with the orange wire.  There were a couple of wire loose off of the circuit board.  Does anyone know the color code/pinout of the circuit board.  PLEASE HELP.  Peace and God bless.

[digi2t]

Dear Sirs,
I have my friends Foxx Gtr Synth that does not work.  There were a few wires unhooked.  We are not sure where the one battery ground goes.  We have one battery + connected to the middle upper terminal of the on/off and the negative goes ?  We have the other battery negative connected to the middle lower terminal of the on/off and the positive goes the the pin 2 of the circuit board with the orange wire.  There were a couple of wire loose off of the circuit board.  Does anyone know the color code/pinout of the circuit board.  PLEASE HELP.  Peace and God bless.

The best I can do is to email you a pdf service manual. Please PM me your email address. It's not the greatest though, the layout image doesn't show the wiring, so the schematic is the only way to go.

If you're not comfortable with this type of circuit tracing, I recommend that you leave it to someone with some experience. Worse case senario, I don't mind doing it for you, but I will ask that you cover the shipping back and forth. That's it. Again, PM me if need be.

Cheers,
Dino

[pinkjimiphoton]

dino,
looky here!!

http://www.ebay.com/itm/1970s-Foxx-Guitar-Synthesizer-I-Studio-Model-9-Project-Broken-Vintage-Pedal-/280986112462?pt=Guitar_Accessories&hash=item416c13d1ce

[digi2t]

Hmmm, veeeery intereeesting. Put it in my watch list, and see where it goes. If it stays low, maybe, but I doubt it will. I did download the pics though. Got a great look at the dual LDR setup, all exposed.

Thanks bro!