Wah Inductor Question

[Joe Hart]

I know that if I build a FF (using the values given in a schematic), then start tossing in random transistors, I will have to change other parts (minimally the bias resistors) to get it to sound good or to even work at all. If I take a wah circuit and start switching random (and unknown value -- not necessarily the suggested 500mH) inductors, will the circuit still work or will I need to start changing other components? In other words, can I just audition the different inductors and get a good feel for how they sound or will I have to start changing other stuff (and thus possibly changing the sound in a way that isn't directly related to the inductor)? Thank you.
-Joe Hart

[Gus]

Change one thing at a time take notes
Take the transistors C,B,E and battery voltage readings before and after to make sure you wired it correcly.  The resistance of the wha inductor is small compaired to the surrounding resistances so you should be able to drop them in place.

  Being inductors the inductance value could be different and you could mistake the inductor changing the sound, What I mean is maybe you could get the same sound if you adjust the sweep cap with a different inductor.  I think it would be interesting to use different core composition part numbers and comparing.

I have used small dip switches setup to add caps in a binary fashion for the sweep cap value.

[Joe Hart]

Being inductors the inductance value could be different and you could mistake the inductor changing the sound, What I mean is maybe you could get the same sound if you adjust the sweep cap with a different inductor.  I think it would be interesting to use different core composition part numbers and comparing.

Okay. So it's not like changing IC's in a TS circuit? I was hoping it was because I have four inductors from an old organ. Oh well. I'll try them anyway and see what happens. Thanks.
-Joe Hart

[Gus]

You can just change them out.  I would also write down the DC resistance value of each inductor.  Are the values close to 500mH?
The inductor wha has a RLC circuit at its core.  You change the L the sweep changes: however you can readjust the C.

  So what are people hearing when they change an inductor in a Wha?  A real tone change due to the core material being different?  A change due to a Q change?  A change due to a sweep change?  The reason I am posting this is I have adjusted the sweep cap value and changed a few parts like the caps but not the inductors in whas that at first did not sound that good, after the changes people were happy the whas.

  One should be able to measure with the right equipment what really is different (if anything but inductance value) between wha inductors.  Maybe a BH plot with controlled drive and inductance change with a very small DC current like in a wha.

[Paul Marossy]

Disclaimer: Wah pedals and what inductor they use is a HIGHLY subjective topic.

Based on my experience with building and tweaking wahs, I have found that the inductor is but just a small part of the sound. The only purpose of the inductor is to make it a resonant circuit. There's not much magical about the actual inductor used. It can be anywhere from 500mH to 1H and it will still sound good.

Case in point: I have an old wah with the "dreaded" TDK5103 inductor in it, totally stock except for true bypassing it. It sounds really good and I think it's the best sounding CryBaby I have. I also have a vintage Italian Vox wah with a red fasel inductor in it, and it's really kind of the lamest sounding of the bunch - too shrill and thin sounding, not really pleasant to play at all.

My conclusion: You can affect more changes in the sound by tweaking the transistors used, messing with the resistor value on Q1, changing the sweep cap, changing or omitting the resistor in parallel with the inductor and what type of 100K pot you use over just changing the inductor. In a wah circuit, it all works together as a whole. Changing one component is not going to magically turn it into a killer wah pedal.

[Joe Hart]

Okay. Cool. I've modded my Vox Wah and I like the sound of it now. I'll try a couple of inductors and see what happens, but I won't have my hopes up for anything dramatic. So, my understanding is that it's similar to a FF in that you can change the "special, magical" element and get a change in sound, but then you can readjust the "boring" parts to get back (or at least close) to where you started anyway. Okay-dokey. I'll stick a late 60's El-Rad 500mH inductor (serious mojo) that I have into it and see what happens. Thanks!
-Joe Hart