My Modded Vox Wah

[Joe Hart]

I modded a Vox Wah and I absolutely love it! I did a true bypass, added an LED (sometimes I leave it on and it's nice to know its status, say, between songs -- before the next song starts and without needing to play around with it between songs!), added a power jack, and did some messing with resistors. I got a sound that I really liked. Then I came across an old Lowrey organ from the late 60's, and decided to mess around with "mojo"! I swapped out some resistors and I'm not convinced that there was a huge difference, good or bad. A couple of resistors did sound worse (probably due to tolerances more than anything), so I put back the original ones. Blah, blah, blah. Then I changed two of the capacitors and the sound became clearer and the little bit of distortion near the mid sweep of the pedal cleared up! I was totally happy!! So, I quit while I was ahead.

Anyway, here's what it looks like. It has a mojo vibe!




You can here it here: http://www.myspace.com/thebluemangoes

I use it on the lead for Y.R.G.M. (You Really Got Me) and the outro lead on W.M.G.G.W (While My Guitar Gently Weeps). And there are no other "added" effects from the rhythm sound to the Wah sound.

Let me know what you think!
-Joe Hart

[richon]

now you can change the 33K resistor for 56K (or 68K, or 51K or anithing near) to get a more vocal Wah sound.

besides , what type of transistors do you have? MPSA18?  Test some lower gain , like BC109B or 2N5088 to have a way more open and organical wah sound. 

[Joe Hart]

So, you don't like how mine sounds. Anyone else? Anyone??  I'm just looking for feedback.  I like it, but maybe I'm in the minority!
-Joe Hart

[richon]

i dind't say "I don't like it", it sounds good....

but I bet this mods I told you would make you happier...

you won't loose much trying them

[Joe Hart]

I tried that mod and liked it better with the 33K in there. I don't know, it was a little more aggressive sounding...

And I didn't mean to be rude, Richon. I did all of the mods that I could find online (and some that I just made up -- but obviously those didn't work well or someone else would have already come up with them!!) and this is what I ended up liking. So when you suggested the "vocal" mod, I figured that you thought mine wasn't "vocal" enough for your tastes. No offense, though! I'm just looking to see what some of the experts here thought of what I came up with. Thank you!!

-Joe Hart

[richon]

don't worry 

and sorry to insist,  but the transistors (lower gain) mod adds a new way of WAHIing.... really...  besides the low notes come clearer and more natural...

just my 2 pesos...


saludos.


do you play your wah with only clean or only overdrive

PS: i just read you can test a different value of the way the wah acts....  do  you have 0.022uf?  maybe test 0.015 to add more highs in your wah sound..

[Joe Hart]

The only thing I didn't mess around with was the inductor and the transistors because I recall reading something where the transistors and inductor were really a distant second to the resistors and capacitors in terms of changing the sound. And it was from someone who is well-respected (like Mark Hammer or R.G. or someone). They said that you could get the same sound with changing resistors around that you could with different transistors.

But you seem to be "insisting," so I will try it. Do you know if I change transistors, will I now have to change resistor values. I know the circuit isn't a Fuzz Face, but in a FF, changing transistor gains means that you have to change other components to get back to a similar sound (aside from just re-biasing). Or and I way off?

In other words, can I just toss in two BC109B's and instant change (hopefully for the better)?  Also, any other transistors I could try? Is it the gain that's important or should it really be the BC109B's? And I know that the "B" at the end is a gain range, I mean other transistors besides BC109's?

Thank you!!
-Joe Hart

[Mich P]

Have a look here to mess with resistors,
it 's very instructive.
http://www.wah-wah.co.uk/index.html
Mich P.

[petemoore]

  I fiddled and fiddled with the circuit, then changed the inductor, the sweep sound became more noticable. Different inductors may for certain change the characteristics.
  Same with transistor swaps, depends one what you want from it. MPSA or lower gain, BC in the Q1 will make it sound...like a BCxxx.
  Choose to stick with or start with a chosen inductor, if 'preliminary' tuning results in weak wah sweep, the inductor might be the thing to change, seems like an easy place to develop pad/trace problems on the typical wah board, change as necessary.
  I found it's difficult to tune a wah, between it's need to be on the floor and the bench, and the wide variety of mods, I think I went for the most pronounced wha sweep tone, I never felt exactly sure that's what I want all the time.
  Some CB's sound fine with the rack re-indexed to the pinion afew times, other times they're just plain weak, a cap swap'll fix it, or may require 1/2 an overhaul.

[richon]

In other words, can I just toss in two BC109B's and instant change (hopefully for the better)?  Also, any other transistors I could try? Is it the gain that's important or should it really be the BC109B's? And I know that the "B" at the end is a gain range, I mean other transistors besides BC109's?

exactly, change transistors and get instant change in sound (for testing purpouse) maybe it's the sound you like better....

the good thing is you don't need to change also resistores to bias them correctly.... 

try some 2n5088 , BC109B, BC547B...  (higher to lower gain) and see how they sound...

i went with almoust Hfe=300 for the perfect sound.

[Paul Marossy]

Blah, blah, blah. Then I changed two of the capacitors and the sound became clearer and the little bit of distortion near the mid sweep of the pedal cleared up! I was totally happy!! So, I quit while I was ahead.

You're a wise man. Sometimes us DIY'ers don't know when to stop.  

The transistor Hfe does matter somewhat in a wah circuit. If you want to experiment with several different types of transistors, put some sockets in. That will save your PCB and make switching out transistors very easy.