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modding a wah-pedal

Discussion in 'Effects [BG]' started by miiitch, Jun 5, 2012.


  1. miiitch

    miiitch

    Nov 27, 2011
    Germany
    cheers

    e2: modded pedal in post #13


    guitar players are obviously too stupid or lazy to help, so I´m just gonna bug you as well:

    I have a wah-pedal, obviously ... this one: http://www.musiciansfriend.com/amplifiers-effects/morley-classic-wah-pedal
    schematics: http://morleypedals.com/pwa.pdf

    but I don´t really want to use it like a guitar-wah, but more like a variable lowpass-filter
    => the wah-boost just below the cutoff-frequency´s still far too strong for me, although the Classic Wah is a rather unobtrusive one .. I don´t need the "cut-through", in fact it´s the last thing I need


    this thread explains how to get into the exact opposite direction: more wah ... I want less wah

    already tweaked the LED, range is good ... i just don´t know how to get rid of that boost

    anyone able to help?



    e: just saw the last link is currently offline, but i kept this:
    I basically need less treble, if that means what I think it does
     
  2. Skrogh

    Skrogh

    Jan 28, 2010
    Denmark
    You want less resonance, or how is that to be understood?
    The "wah" is already working as a low-pass filter, but the resonance is frequency dependent, so it's a bit hard to increase or reduce in a good way. One way you can limit it is by inserting a resistor in serial with C6. Try with 10K or 100k, more resistance means less resonance. Remove C1 to get rid of the treble boost it provides. Try Googeing "Tim Escobedo's Q+D VCF"

    Good luck modding
     
  3. miiitch

    miiitch

    Nov 27, 2011
    Germany
    yup, resonance might be what i was looking for, sounds great
    what i meant was the (low- to hi-)mid bump just before the cutoff

    i´ll try to add a resistor when i´m at home again
    could you explain what part of the circuit has an effect on resonance? i´m not so much into electronics
     
  4. Skrogh

    Skrogh

    Jan 28, 2010
    Denmark
    I honestly don't know much about the t-filters. but putting in a resistor there will def. limit resonance. There is another way to increase it, but that is kind of irrelevant. When you get home do a google for "Tim Escobedo's Q+D VCF" there is some info about this kind of filters there.
     
  5. miiitch

    miiitch

    Nov 27, 2011
    Germany
    alright, i put in a 10k resistor

    tone changed, but i need some more values to try ... maybe i´m gonna make them switchable as well


    e: noise problem gone
     
  6. I did this and got what I wanted, although the WAH is still weaker than I feel it should be, as a notch or freq attenuator, it's great::::

    100_7346.jpg

    It's just a piggy-back .1uF cap attachment to that other cap.

    Maybe this link can help a little:::

    http://www.diyguitarist.com/DIYStompboxes/WahMod.htm
     
  7. Remember that a wah is a bandpass filter, NOT a lowpass filter... Changing resistor values won't change the design.
     
  8. miiitch

    miiitch

    Nov 27, 2011
    Germany
    i can´t remember that, because i never knew ;)
    mine has plenty of bottom end in every position though
    =>
    I DO WANT less wah, less vocal-sound .. what I understood from your post is the opposite, am I wrong?
     

  9. I may not have typed what I was thinking.

    The Wah had weak response in the 40-60 Hz range as it originally was, but adding that cap took it into the zone a lot better - the zone here is where my E string was sounding.

    This was a guitar Wah, not a bass Wah, so I was just trying to get it to work at the lower freqs. That part came out fine, although the actual wah-ability wasn't changed all that much.

    It could just get to the range I needed now.

    In the past I've used a Wah as a Notch filter that I could adjust as I felt it needed to be for whatever reason I might have.

    Envision of it like this: a telephone doesn't reproduce all the freqs of normal speech, and this mod to a Wah kinda gives that same effect, although it is much more adjustable.

    In any case - it's a quick-n-dirty test to see if that is what you want. Maybe 10 minutes before you even take the feet off the base.
     
  10. miiitch

    miiitch

    Nov 27, 2011
    Germany
    i guess that´s not what i need, but thanks anyway :)

    since I´m playing through a tube pedal, which literally eats the low end, i probably didn´t notice any change in bass response ... if there is any, I don´t care :D


    all I want is to soften, or possibly remove, that resonance peak, and it seems like the resistor n series to C6 does that (but i´m not quite sure yet, noise problems -.-´)


    e: noise problems gone!
    i put some plastic foil between the circuit board and the metal housing, now the ultra-loud hum is gone :)
     
  11. Skrogh

    Skrogh

    Jan 28, 2010
    Denmark
    That looks like a crybaby or voxwah to me. The circuit in that is way different from the one miiitch has. A crybaby is a resonant bandpass, the one in question is indeed a lowpass filter.
    @Miiitch you could substitude the resistor with a 100k potmeter, this way you can vary the resonance from high to low :) wire it up so the middle and left lug is connected (pin facing your way, lugs facing down) where one of the resistors legs were and the right lugs is at the other leg. I hope I'm making myself understandable, if not i can probably make a drawing pretty easily.
     
  12. miiitch

    miiitch

    Nov 27, 2011
    Germany
    yeah that was what I wanted to do :)
    at first I thought of a mini rotary switch with 5-6 different resistors, but a pot is so much easier to do

    and when I´m already modding it, I´m gonna make C1 switchable ;)

    any other things worth modding? maybe the LED resistor, when I´m gonna have a power supply with adjustable output voltage?
    oh, a volume pot would be useful :) there´s a fixed resistor in my pedal
     
  13. miiitch

    miiitch

    Nov 27, 2011
    Germany
    it works :) yay! thanks a lot


    added volume, range and resonance knob .. the shop didn´t have C-pots, so I put in the 3 pots and done

    - LED resistor from 4,7k to 1,5-24k (range control)
    - P1 + R7 didn´t exist like it´s in the schematics, changed from 6,8k to 2,4-25k (volume control)
    - 220k-pot in series to C6 (resonance control)


    some audio:
    turned the volume pot, then added resonance and turned the range knob, using the footpedal at the end


    chain: bass - overdrive - wah - tube pedal - laptop (cab simulation) ... that´s the way i want to use it (except for the sim)
     

    Attached Files:

    Last edited by a moderator: Apr 16, 2014
  14. Darren3456

    Darren3456

    Aug 13, 2015
    Miiitch, I'm currently looking to mod a Morley wah to achieve the same effect as you (less of that peaky Q in the sound)...would you be interested in telling me the part you soldered in to soften that resonant peak? Also interested in adding a pot to control it, as you did. I'm a modding novice and just need to know what to solder where, parts to buy, etc. and a photograph would be definitely helpful.

    Thanks for your time D




     
  15. Darren3456

    Darren3456

    Aug 13, 2015
    THANKS for the information Miiitch! d


     
  16. miiitch

    miiitch

    Nov 27, 2011
    Germany
    sorry, was reading for weeks without being logged in at all :cool:

    schematics: http://morleypedals.com/pwa.pdf

    220k-pot in series to C6 (resonance control). That´s all. Basically you just clip off one leg of the capacitor C6, solder a wire to the cutoff-leg and a second wire to where you clipped that leg off. Attach these wires to the 220k-pot (left and center, or right and center), and you´re ready :thumbsup:

    i highly recommend the range mod, too! (exchange fixed 4,7k LED resistor with a fixed 1.5k + added 22k pot (range control))
     
    Last edited: Sep 2, 2015

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