Wah pedal help?

[nick12391]

I've thrown together this circuit on the breadboard. The signal comes through beautifully,  but the wah effect is barely noticeable. I might even be imagining it. I've checked all my components and connections. And I've changed the pot to a 200k and a 1.5M with no noticeable change. Any ideas what the problem could be? Does anyone have voltage test points I could check against?
Thanks!

http://www.geofex.com/article_folders/wahpedl/wahped.htm

[nick12391]

Here are some points I checked:

Battery: 8.5V

Q1
C: 5.2V
B: .68V
E: .065V

Q2
C: 8.1V
B: 4.0V
E: 3.5V

[GibsonGM]

What're you using for an inductor, Nick?
How about transistors, which ones?

This works, I've also done it on BB, with a real wah inductor.  My first inclination would be to think there's a wiring error, our most common problem! So double check EVERYTHING.... is the .22u cap on Q2? The base voltage is calling out to me as high - something seems wrong in that region...double check ALL connections to it.   Maybe that's yer trouble....

[nick12391]

What're you using for an inductor, Nick?
How about transistors, which ones?

This works, I've also done it on BB, with a real wah inductor.  My first inclination would be to think there's a wiring error, our most common problem! So double check EVERYTHING.... is the .22u cap on Q2? The base voltage is calling out to me as high - something seems wrong in that region...double check ALL connections to it.   Maybe that's yer trouble....

Thanks for the response! I'm using five 104j inductors strung in series, since that was all I had. My transistors are brand new 2N3904's. I've double and triple checked all the connections; the base of Q2 is connected to the .22u cap and a 470k resistor.

[GibsonGM]

I'd get an actual wah inductor, that's where most of my suspicion is.  I mean, are they really inductors, or CHOKES?    Since you have signal, it's a reasonable bet....you can also audio probe the signal path just to assure yourself that amplification is happening with the transistors, while you wait for an inductor! 

[nick12391]

I'd get an actual wah inductor, that's where most of my suspicion is.  I mean, are they really inductors, or CHOKES?    Since you have signal, it's a reasonable bet....you can also audio probe the signal path just to assure yourself that amplification is happening with the transistors, while you wait for an inductor! 

Thanks I'll try that. Out of curiosity, how is a wah inductor different from a regular inductor?

[GibsonGM]

I don't think it is, other than perhaps the DC resistance...the way it's constructed could affect that.   What I'm not that sure about is what you actually have...if they were RF chokes, they'd have a different core material.   If you are sure of what you have, then perhaps they SHOULD work with a wah - I really don't know if there's some magical reason why not, but they are the 1 thing you substituted - that's why I'm focused on them.

Inductors have some weird properties about them, LOL.

Edit: I think different types of inductors may have a different Q to them....

If it were me, I'd go thru the transistor stages and be sure they're amplifying...and any wiring error at all could result in your problem!

[PRR]

> I'm using five 104j inductors strung in series

Good inductance. The DCR may be 700 Ohms, too high to get strong resonance, which echoes your observed sound.

But as always: wiring error!
____________

> are they really inductors, or CHOKES?

Same thing. Like scallions and western onions. "Inductor" is general, "choke" is a circuit function.

[nick12391]

Thanks, guys. I'll quadruple check my connections and check the DCR on my inductor. I ordered a fasel so when that gets here I'll toss it in and see if that fixes it. I'll let you know what happens.

[GibsonGM]

Ah, so no core differences between choke & inductor?  I never did get that sorted out!

DCR was my guess, if all else is wired and working...

[nick12391]

Hi guys, so it turns out I had a 330 ohm resistor where I should have had a 33k  . Swapped it out and it works great. I added the fasel and it sounds even better! Thanks for the help!

[GibsonGM]

Hi guys, so it turns out I had a 330 ohm resistor where I should have had a 33k  . Swapped it out and it works great. I added the fasel and it sounds even better! Thanks for the help!

That's usually the problem, Nick!  Human error...we all do it. Glad it works, enjoy the wah and the forum!