Bass wah in auto mode

Discussion in 'The Projects Forum' started by imperatormk, May 23, 2014.

  1. imperatormk

    Thread Starter Member

    Mar 1, 2011
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    2
    Hey.

    I found this bass wah schematic online (in attachments), but it has a switch that is supposed to simulate the actual pedal for activating the effect.

    I was wondering if I can modify the schematic so it works in auto mode (no external trigger is needed). As I don't know much about this circuit, the best I can think of is feeding the input signal to the point where the foot switch is, so it would be activated whenever something is played. This of course might be utterly wrong.

    Any suggestions appreciated!
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    A circuit addition could probably do that, but are you sure that you want the wah effect permanently active? Or did you mean to activate it for a given time, or in response to a certain input level?
     
  3. imperatormk

    Thread Starter Member

    Mar 1, 2011
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    2
    Just it needs to simulate what the Auto mode on commercial wahs does. I would say it's permanently active, just not sure about the way of triggering. I was also thinking about inserting a 555 IC in astable mode in the circuit, so it would do the same as periodical press of the switch, but again it's a long shot since I don't have enough info on how it actually functions.

    Thanks!
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I'm not familiar with commercial wahs, so sorry, can't help you there.
     
  5. bertus

    Administrator

    Apr 5, 2008
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  6. imperatormk

    Thread Starter Member

    Mar 1, 2011
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    Hey.

    So I found an auto-wah schematic after all, similar to the one I have posted previously.

    However, there are some capacitors on it that don't have the capacitance measure unit, just the value.

    Here it is:

    http://prntscr.com/3ns8ot (the values marked with green are the problem).

    My guess is that those are uF, but I just can't do without a verification of someone more experienced.

    Thanks!
     
    Last edited: May 29, 2014
  7. alfacliff

    Well-Known Member

    Dec 13, 2013
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    yes, those are in micro farad.
     
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  8. bertus

    Administrator

    Apr 5, 2008
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  9. Veracohr

    Well-Known Member

    Jan 3, 2011
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    Without looking into it much, I think you'd want an oscillator (sine or triangle) as the modulation source, and if you wanted it to be an envelope-controlled wah (I don't know much about 'auto' wahs), you'd want an envelope follower controlling a VCA after the oscillator.
     
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  10. imperatormk

    Thread Starter Member

    Mar 1, 2011
    96
    2
    Hey. So I built the circuit given here: http://members.shaw.ca/roma/wah-4.gif .. but it doesn't seem to work as expected. It just acts like a alternating switch (passes the original signal for some short time, then it mutes the output, pulsing like that all the time).

    I double-checked the board against the schematic and it looks alright. Does anyone have a clue what might be wrong?

    Thanks!
     
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