Expression pedal calibration - how is it supposed to work

  • Hi guys,


    Just modded my Vox Wah into an expression pedal. However it is not using the full range and most of the action happens at the last few "toe" centimeters.


    I tried to go into system settings to calibrate but I'm not even sure how to use the calibration feature. Nothing happens/changes if I click and/or hold the soft-button:



    How is it supposed to work, what should I be seeing, and why isn't it working :)


    Any help appreciated.

    Kemper PowerRack |Kemper Stage| Rivera 4x12 V30 cab | Yamaha DXR10 pair | UA Apollo Twin Duo | Adam A7X | Cubase DAW
    Fender Telecaster 62 re-issue chambered mahogany | Kramer! (1988 or so...) | Gibson Les Paul R7 | Fender Stratocaster HBS-1 Classic Relic Custom Shop | LTD EC-1000 Evertune | 1988 Desert Yellow JEM

  • Thanks. Is it important to only do that one sweep?


    Doesn't t seem to change anything too. (like in their video)

    Kemper PowerRack |Kemper Stage| Rivera 4x12 V30 cab | Yamaha DXR10 pair | UA Apollo Twin Duo | Adam A7X | Cubase DAW
    Fender Telecaster 62 re-issue chambered mahogany | Kramer! (1988 or so...) | Gibson Les Paul R7 | Fender Stratocaster HBS-1 Classic Relic Custom Shop | LTD EC-1000 Evertune | 1988 Desert Yellow JEM

  • Yes, you need an TRS cable. Look at the page in front of of the switch menue and move the pedal. You must see that the meter deflection goes from 0 to 127 when using the pedal. Hope that meter deflection is the right word for it. Is the pedal setted to vol or wah?

  • If you're getting something that's strange... any trim pots inside to tweak the sweep? Are you using a TRS cable as I'm pretty sure the KPA requires one?

    Yes I am but thanks for the suggestion.

    Kemper PowerRack |Kemper Stage| Rivera 4x12 V30 cab | Yamaha DXR10 pair | UA Apollo Twin Duo | Adam A7X | Cubase DAW
    Fender Telecaster 62 re-issue chambered mahogany | Kramer! (1988 or so...) | Gibson Les Paul R7 | Fender Stratocaster HBS-1 Classic Relic Custom Shop | LTD EC-1000 Evertune | 1988 Desert Yellow JEM

  • Sorry, I have just seen that you used it for morphing. Did you set morphing in some parameters to hear if it works? Otherwise choose volume pedal to check if it works right.

    Yes I have tried it. But as stated all the action happens close to toe position.

    Kemper PowerRack |Kemper Stage| Rivera 4x12 V30 cab | Yamaha DXR10 pair | UA Apollo Twin Duo | Adam A7X | Cubase DAW
    Fender Telecaster 62 re-issue chambered mahogany | Kramer! (1988 or so...) | Gibson Les Paul R7 | Fender Stratocaster HBS-1 Classic Relic Custom Shop | LTD EC-1000 Evertune | 1988 Desert Yellow JEM

  • Thanks for the suggestions all. I think I figured it out. Calibration doesn't work the way we think:


    You have to click once to start it at heel position and then again once at toe position.


    In the video below even at full toe position the calibration graph only reaches around 90%. Then I try 3 things:


    1. I click and hold the button at heel position, move to toe position and release the button. Result: No change - pedal still only covering 95% range.
    2. Then I click and hold the button at heel position, move back and forth a few times and release the button. Result: No change - pedal still only covering 95% range.
    3. Then I click once at heel position, move to toe position, and click again: Result: Now the pedal covers the full range.



    This is the line from the manual which I think is either insufficient or plain wrong: "Then, press and hold the soft button “Calibrate” while sweeping the pedal completely from heel through to toe position".

    Kemper PowerRack |Kemper Stage| Rivera 4x12 V30 cab | Yamaha DXR10 pair | UA Apollo Twin Duo | Adam A7X | Cubase DAW
    Fender Telecaster 62 re-issue chambered mahogany | Kramer! (1988 or so...) | Gibson Les Paul R7 | Fender Stratocaster HBS-1 Classic Relic Custom Shop | LTD EC-1000 Evertune | 1988 Desert Yellow JEM

  • and you have chosen pedal typ 1 as far as i can see (-;

  • Yes :). But even then the click and hold approach doesn't work. Check the video :)

    Kemper PowerRack |Kemper Stage| Rivera 4x12 V30 cab | Yamaha DXR10 pair | UA Apollo Twin Duo | Adam A7X | Cubase DAW
    Fender Telecaster 62 re-issue chambered mahogany | Kramer! (1988 or so...) | Gibson Les Paul R7 | Fender Stratocaster HBS-1 Classic Relic Custom Shop | LTD EC-1000 Evertune | 1988 Desert Yellow JEM

  • This is what the Reference Manual says in chapter "Expression Pedals and Foot Switches":


    ...., you just need to plug in the TRS-cable,press “Calibrate” and perform a full swell on the pedal to calibrate it.


    In addition the Profiler performs an ongoing calibration. If it should turn out, that suddenly your pedal can even cover a wider resistance range, the Profiler will recognize and adapt to it.


    If you have issues with your modded Vox pedal, please check with a standard expression pedal in order to have a reference.

  • Thanks Burkhard. I was tricked by the manual mentioning holding the calibrate button elsewhere which doesn't seem to work (for me at least).

    Kemper PowerRack |Kemper Stage| Rivera 4x12 V30 cab | Yamaha DXR10 pair | UA Apollo Twin Duo | Adam A7X | Cubase DAW
    Fender Telecaster 62 re-issue chambered mahogany | Kramer! (1988 or so...) | Gibson Les Paul R7 | Fender Stratocaster HBS-1 Classic Relic Custom Shop | LTD EC-1000 Evertune | 1988 Desert Yellow JEM

  • I just modded my broken Cry Baby, too and have the same behaviour. I just can´t calibrate it proberly. Did you found a solution?

    Check the video above. You should not hold the button down. Instead click it once in each pedal position.


    Works for me at least.

    Kemper PowerRack |Kemper Stage| Rivera 4x12 V30 cab | Yamaha DXR10 pair | UA Apollo Twin Duo | Adam A7X | Cubase DAW
    Fender Telecaster 62 re-issue chambered mahogany | Kramer! (1988 or so...) | Gibson Les Paul R7 | Fender Stratocaster HBS-1 Classic Relic Custom Shop | LTD EC-1000 Evertune | 1988 Desert Yellow JEM

  • I just modded my broken Cry Baby, too and have the same behaviour. I just can´t calibrate it proberly. Did you found a solution?

    l have experienced a similar issue. As burkard, said there is an on going auto calibration looking for the maximum upper and lower limits with which the KPA self-adapts to.
    This has a side effect in that if your pot is not sweeping through 100% of its range it needs to be calibrated to this "limited" range. However, unplugging the pedal may momentarily 'give' the KPA a false upper/lower maximum value that the KPA then assumes as the "new" upper/lower limit, thus needing recalibrating.
    This is true for "regular" pots that work over 290 degrees rotation/full-sweep. Some expression pedals and wah pots work over a 90 degree turn for their full range.
    I done a video on this issue a while back, here:


    Then again, it could be a dirty potentiometer in your case or bad connection on the plug or socket connecting your pedal?

  • Great video - thanks for sharing.

    Kemper PowerRack |Kemper Stage| Rivera 4x12 V30 cab | Yamaha DXR10 pair | UA Apollo Twin Duo | Adam A7X | Cubase DAW
    Fender Telecaster 62 re-issue chambered mahogany | Kramer! (1988 or so...) | Gibson Les Paul R7 | Fender Stratocaster HBS-1 Classic Relic Custom Shop | LTD EC-1000 Evertune | 1988 Desert Yellow JEM

  • musicmad, big thanks, you saved my day with your exact explanation of how to calibrate the expression pedal. I was about to sell my Mission Engineering EP1-KP because I couldn't get the calibration beyond 117 and apparently it won't do morphing until it gets the full range of 127... that is, until I stumbled on this thread. This is not the only flaw in the Kemper manual that could use a revision as far as clear explanation regarding some functions goes. There's e.g. a lot of confusion also between Speaker Out (extra out on the amped Kemper) and Monitor Out.