Lowaht Wah circuit for Toe Jam...

[Earthscum]

So, this is the circuit I made for my "Toe Jam Wah" 1590A wah pedal.



I basically started with the goal of making the most power efficient LDR-based wah circuit I could. The biggest concern was the LED, which just happened  to be not much of a concern at all. I tried a bunch of LED's at 47k (9V supply), and found the bright white ones from Tayda worked great! Most of them start to get a noticeable dimming out around 75-100k, but not enough to affect the action of the circuit.

The transistor should bias dead-nuts at 4.5V with a 9V supply, and about 6.1V with a A23 (12V) battery. The A23 is rated for about 35mAH... this circuit should give you a ton of playing time, even on the tiny batteries. That's where the name comes from... Low Wattage T-filter Wah = Lowaht   

[Joecool85]

I may be building a wah later...

[drhulsey]

Very Cool!
You might be able to increase your travel by increasing the distance between the top
of the treadle and the pivot point. That raises the treadle somewhat.
You would gain more room inside without the battery (obviously!) and by putting the
supports for the treadle outside the box (might simplify fabrication, as well).
Although, I'm not sure it would keep the aesthetic look you have created
Thanks for sharing!

[Govmnt_Lacky]

I am kind of a noob when it comes to LDRs and how they perform in a Wah circuit 

Could someone please give me a short explanation on how... with this particular circuit.... the LDR is used to make the wah... WAH?

Are you just varying the resistance to the LED to make it brighter/dimmer?

Thanks for the pity knowledge 

[Earthscum]

With this style of Wah, the LED and LDR are facing each-other, and a mechanism is used to block the light. When the light gets blocked, the LDR goes to high resistance, dropping the frequency corner lower. When the block is removed, the LDR gets light and goes to low resistance, making the frequency sweep higher.

Next one I do, I'm tapping everything instead of using nuts... I lost a good CC of space from those things. The sweep is actually not too bad... I can increase the effect pretty easily by just swapping out the 100k LED resistor to about 75k. Basically, the mechanical sweep is nearly perfect... I don't have nearly the amount of dead area at the bottom or top that I see with most wahs (especially my modded FX-17). Even with the apparent short treadle travel, it feels so much more controllable than my FX17, my buddy's Morley Power-Wah, or my drummer's crybaby. Definitely a perfect "sock" pedal, lol... I can control it with my big toe. Last night was the first time I tried it with shoes on... I felt like I was squashing a bug, or stepping on equipment I wasn't supposed to, lol.

[joegagan]

wow i went and looked at the build pics. very impressive indeed

aren't those batteries like 10 dollars each? i have a flashlight here that i refuse to put a battery in after i tried to buy one.

[Earthscum]

wow i went and looked at the build pics. very impressive indeed

aren't those batteries like 10 dollars each? i have a flashlight here that i refuse to put a battery in after i tried to buy one.

thank you, and those batteries were about $4 for a pair at the grocerie store... Duracell even. I had to buy one for the door bell and had a second one floating around. I came across Tubelectron's 1590 with the battery and knew what I wanted to do with my first case. I was kinda irked that I had to buy 2, but now I'm totally happy about it, lol.

[drhulsey]

... Next one I do, I'm tapping everything instead of using nuts...

There should be sufficient thickness to tap and get some stability. It will be interesting to see how it stands up to wear and tear.

I felt like I was squashing a bug, or stepping on equipment I wasn't supposed to...

It would take some getting used to. I really would like to do an entire pedal board with 1590A  pedals, all hooked up to a multichannel looper. I could eliminate the Switch on the wah pedal, altogether. Since I would have 1/4" jacks for in and out of the looper, I could use my idea for 3.5mm plugs/jacks in the pedals themselves. That would really open up some room!

[Earthscum]

I was surprised at how good it feels. With socks on, you can literally use your big toe. With shoes, you just ignore how small it is and find your spot, and it is basically (lock to lock) similar to the break-over point on a crybaby's sweep, as best as I can explain it.

---

I actually jumped on to mention some notes.

You can tune the tone at the top end of the sweep by adjusting the 1uF emitter cap. Ideal for bass, IMHO, should be 1.5uF, but I don't have one to test for sure. I tried a 1uF and .47u paralleled. 2.2 just had the wrong tone and I wanted to stab it in the face with a soldering iron.

Basically it seems to give it more 'Q' as it sweeps up. Higher value caps (4.7uF, 10uF tested) make the Q about the same throughout the range, while smaller (.68u,  .47u, .33u, .22u, .1u tested) make the Q bunch up at the top of the sweep. Guitar may respond better to the .68u.

Another note. For guitar, I found that changing the feedback cap on the collector side to 680p sounds more pleasing, and if you want a deeper tone for bass, change the cap on the base side to 1.5n or 2.2n.

These mods should work good together, i.e. .68u emitter cap and the 680p cap, or the 1.5u and 1.5nF.

If you want to increase the effect even more, you can try increasing the 1M input, or decreasing the 100k to ground a bit. This drops the output volume, but makes the effect more apparent. Decreasing the 1M much lower starts to bring in the distortion (at 9V). At the 12V supply it may have a bit more wiggle room. I played a teeter-totter game for awhile between distortion coloring quacks and clean, big sweeps until I got the right component combination.

These are all things I found while tuning the circuit, but I figure a nice, reliable middle ground is the best starting place for others.

[azrael]

What I'm most interested in is how you modified a 1590A into a wah rocker, and how you are implementing a wah pot. 

[ItZaLLgOOd]

If you look in the first post there is a link.

[azrael]

Um, I know that....It's just pictures, though. Doesn't show how he laid it out inside the box, or how he decided to cut the box, and what he use to make the rocker mechanism...

I only don't like that the rocker is used to physically block light, this means that it won't be all that useful onstage.

[Earthscum]

Um, I know that....It's just pictures, though. Doesn't show how he laid it out inside the box, or how he decided to cut the box, and what he use to make the rocker mechanism...

I only don't like that the rocker is used to physically block light, this means that it won't be all that useful onstage.

Here's the details to look for in the pictures:

the rocker is just 1/8in aluminum. I tapped the top so the machine screw would cinch down without a nut. It just goes through a hole in the plate, which is bolted to the box. This is where I wish I would've tapped instead of using nuts. It would give me an extra quarter inch of board space.

If you look close you can see that I have a pin that runs from the heel of the treadle plate through a hole in the top. This pin runs against a piece of felt on the unside of the box and has pressure against it from the board, where a notch is cut in and also covered with felt.

The pin moves a flapper inside that blocks the light. The LED is wrapped in an aluminum tube to help direct the light, avoiding contamination from reflected light inside the box.

As you can now see,  I am well aware of the problems with LED/LDR based wahs, and took care of a couple issues. I can shine a spotlight anywhere on this thing and it won't make the slightest glitch. Solid, lol.

Oh yeah... Believe it or not, I cut this case by hand with a hacksaw. It was the only thing that was thin enough. That sixteenth of aqn inch really hurt me on space, that's the reason for the aluminum spacer on the bottom plate. It is 1/8 inch.

[azrael]

um, wow, i think i'm gonna need a bit more documentation than that to figure out how to build my own, sounds like quite a bit of clever engineering! 

[Joecool85]

um, wow, i think i'm gonna need a bit more documentation than that to figure out how to build my own, sounds like quite a bit of clever engineering! 

That's what I was thinking.  Regardless, I'm still thoroughly impressed.

[giappui]

have you tried to use a 100k pot to adjust the  led brightness?