Building a wah!

[SamanthaCay]

So I bought a broken crybaby 105Q with the hope that it could be fixed and as it would turn out it can't.

It's all micro circuitry in there and after testing/replacing all the serviceable components to no avail, I've decided to salvage the housing and most of the hardware involved and start fresh.

With that the search for a simple yet effective circuit began.

I stumbled upon this circuit and after some consideration and research I think this might just work.
Also I should mention that this is slightly modified from what I originally found.


It's based off an early Vox wah only I've changed one of the caps (Cf) from a .01uf to a .033uf in the hopes that it's sweep will be more in the usable range for bass, if anyone has any better subjections in that regard let me know.
As to be honest although I know that this is the cap to change the sweep with, I kind of took a guess as to what to change it to.

The two other things that differ from the original circuit is first, the wah pot I have is 20k not 100k (hoping that works) and second, the transistors.
The schematic I found didn't specify what to use, but through a little home work I found that a 2N5088 should work, I hope so because I have some already.

Anyways with that out there do any of you have any subjections?

I guess I should mention at this point that although I'm not a total noob to electronics (I've been working on basses and guitars for years) I'm also not so experienced in the way of circuit design so you'll have to bare with me if I ask a lot of stupid questions.

Last I'll just go ahead and mention where I'm at with this.
With what I currently have laid out, I have all the parts aside from the pcb (which I intend to make from scratch) and the inductor, which if things work out I should have one in a week from a friend who switched one out on his crybaby.

The other thing I've gotten done is this pcb layout, it may not make a lot of sense as most of the components are not labeled but if I look at the schematic and then at the layout it works.

Oh and Fyi the reason that Rc1 is so big is because it's a big old school resister I really raided the parts pile for this one LOL.

[Silver Blues]

Lol cool! I saw this same article and was wondering how it would turn out implemented as a bass-oriented circuit, I'll be following your build and see how it works!

Good luck with it!

--Silvie

[SamanthaCay]

Progress!
Here is the board I made using copper tape laid over a piece of counter to laminate, I choose this method because it was stuff I had on hand (I'm a cheap wad) but I soon realized this was a pretty poor choice.
When I solder it melts the copper tape's adhesive and the copper wants to curl up.
This makes working with it a pain.

Although as luck would have it, I'll have to make a new board anyhow.
I got my inductor yesterday and started work on this finally.
One major flaw with the current board is there is not enough room for the inductor, so for now I have it run to the board with a couple of jumpers.

Now here's a short run down of what has taken place thus far.
I'll start by saying this was a lot more work then I would have thought.
I worked on this thing for about six hours yesterday and I'm still not quite there.

The first thing I got with the circuit above was a very slight tonal change, so naturally I started ramping up cf by placing higher value caps in parallel, it got better but no cigar.
The sweep was to narrow so I then changed Re1 from a 470 to a 1k and that made a hell of a difference!
The range was much better but it was picking up a radio station, EKE!
To my surprise that was a very easy fix, all I had to do was ground the dam thing, derp.

The last thing I did yesterday was to change out Rq for a larger value as the wah was kind of bland and this is the one to change to increase/decrease the peak resonance.
I went with a 100k on this which is a bit too much, the wah is way to harsh sounding now.

So with all that out there where I'm at now is I'm looking at making Re1 a little bigger say like in the 1.5/2k range, as the sweep still isn't quite wide enough, and finding some middle ground as far as Rq is concerned.

Once I get a working prototype I'll then figure out something better for the board.

Till next time...

[BawanaRik]

Good Luck with the build. Please keep us in the loop.

I am always impressed by creativity.

[seanm]

What bass are you using this with? It has a very very low input impedance. Even for an active it might be low.

I would seriously think about putting an input buffer in front of this.A simple FET one would be fine.

[Silver Blues]

Originally Posted by seanm

What bass are you using this with? It has a very very low input impedance. Even for an active it might be low.

I would seriously think about putting an input buffer in front of this.A simple FET one would be fine.

Yeah +1. This is a good suggestion.

--Silvie

[SamanthaCay]

Originally Posted by seanm

What bass are you using this with? It has a very very low input impedance. Even for an active it might be low.

I would seriously think about putting an input buffer in front of this.A simple FET one would be fine.

That's a very good point.
I'm using a passive p bass.

Also that reminds me of something else I ended up changing yesterday.
With Rin I went from 68k to a 22k and that helped a lot.
It's still not quite as loud as it should be but it's pretty close.

I may end up trying an even smaller value and if that doesn't work I'll go ahead and buffer the input.

For now though my main focus is getting the sweep where I want it.
I think I went way to far yesterday with cf and Re1.
My first thought was that I hadn't gone far enough but after playing through it for a few I ended up going back to my original values on those two and it sounds a lot better.

I haven't even messed with Rq since yesterday and at this point I'm not sure I should, after all it seems this is the best mod I've done!
The harshness went away by bringing the sweep back to it's original place.
So what I thought was the sweep being way off was really the peak resonance being off.

At this point it's real close to where I want it, I'm thinking a small change to cf say, .05 might just do it.
we'll see.

I guess what I'm taking away from this at this point is that with all the values here, a little tends to go a long way and if one small change doesn't do it it's probably something else.
I went way to far with cf and Re1 yesterday just because rq wasn't right.

This is one hell of a learning experience.

[seanm]

Originally Posted by SamanthaCay

That's a very good point.
I'm using a passive p bass.

Also that reminds me of something else I ended up changing yesterday.
With Rin I went from 68k to a 22k and that helped a lot.
It's still not quite as loud as it should be but it's pretty close.

I may end up trying an even smaller value and if that doesn't work I'll go ahead and buffer the input.

I am not 100% positive, but I believe you can drop Rin altogether.