Gain control with expression pedal

  • Hello, I would really like to control the amp gain with a expression pedal.


    This is a feature that was available on some mesa boogie mark II amps see this link


    William G. Sacks has written, "A cool and little-known option with the Mark IIB (or original Mark II): while the effects loop isn't worth much as such, you can run the output of a volume pedal (without your guitar being plugged into its input) into the 'return' jack, and get on-the-fly preamp gain control! This is a feature that very few tube amps have ever had, even inadvertently - it uses the pot in the volume pedal as a passive limiting device, such that when the pedal is 'wide open,' it allows the preamp tubes' full voltage to pass into the power section. As the pedal is backed off, it decreases the amount of preamp signal allowed through the 'loop,' cleaning up the sound. One of my best friends sets his clean channel's preamp to 9 and uses an Ernie Ball pedal to vary the overall tone. Oh, I wish we could convince Mesa to make this a regular option on their new models..."


    While I didn't own this amp I've used this feature on a digitech RP 500 where you can assign almost EVERY parameter to the exp pedal. The result is incredible since you can have so much variety in a single patch, great for blues and jimi songs.


    The added bonus is that you can let ring a single note and press your exp pedal down while it fades out for ultimate sustain , feedback & great larsen. Not to mention that you can switch from rythm to lead as you do with your volume pot but with great clarity without adding mudiness. To compensate for the changes in volume, a 2nd exp pedal could be used.


    going further, it would be great to be able to control more parameters on the kpa with the exp. pedal.


    Hope you'll enjoy this great feature.

  • If you assign the volume pedal pre-amp (Rig menu) then you'll achieve what you're looking for (adjust the Gain to accommodate for it)

    "Music is enough for a lifetime, but a lifetime is not enough for music" Serghei Rachmaninoff


  • Rig Menu, Page 3, first dial under the screen ("location"). Turn it to "post stomps" (Sorry, that is what I meant with "pre-amp" = before the stack and after the stomps)

    "Music is enough for a lifetime, but a lifetime is not enough for music" Serghei Rachmaninoff


  • Al rite !


    I have fount it but I can only adjust my volume but not my gain with the pedal , achieving blackmoresque violin sounds ;)


    How can I assign it to the gain control ?? I could'nt accomodate it like u told me :huh:


    Renaud.


    edit : Ok I now understand , on distorded sounds pre amp volume acts like a gain, but the gain leds to not change , as I was expecting. In this setup the gain knob acts as a limit to the range of the pedal. This is great for switching from rythm to lead , Thanks !


    I guess my original request is still valid , as it would be cool to have the actual gain modified by the pedal.

  • on distorded sounds pre amp volume acts like a gain, but the gain leds to not change

    In the Rig menue page 3/3 the "Range" parameter changes this behaviour. Set it to -5 and the pedal will be silent in the heel down position and fully open in the toe position. As you probably don't want the gain to be silent raise the value again to what you want for minimum range.


    You can do the same with the "Wah Pedal Booster" (assign the EXP pedal to "Wah" and then chose a "Wah Pedal Booster" in the stomp section) but here the terminology is inconsistant and parameters have swapped the names for whatever reason: here you set minimum value with the "Volume" parameter and the maximum value with the "Pedal Range" parameter. This is not logical but is works. ;)


    going further, it would be great to be able to control more parameters on the kpa with the exp. pedal.


    Yeah!!! :thumbup:

    www.audiosemantics.de
    I have been away for quite a while. A few years ago I sold my KPA and since then played my own small tube amp with a Bad Cat Unleash. Now I am back because the DI-profile that I made from my amp sounds very much convincing to me.

  • hello , I've been testig both solutions, I'm totally in love with the wha booster , it's a fantastic way to discover the incredible tone range on a single amp, from clean , crunchy to super lead just with a subtle amount of the foot press, mighty great feature M Kemper !!! :thumbsup:


    Thanks a lot guys for your explanations, I'll now need 1 more expression pedal.


    R.

  • In the Rig menue page 3/3 the "Range" parameter changes this behaviour. Set it to -5 and the pedal will be silent in the heel down position and fully open in the toe position. As you probably don't want the gain to be silent raise the value again to what you want for minimum range.


    You can do the same with the "Wah Pedal Booster" (assign the EXP pedal to "Wah" and then chose a "Wah Pedal Booster" in the stomp section) but here the terminology is inconsistant and parameters have swapped the names for whatever reason: here you set minimum value with the "Volume" parameter and the maximum value with the "Pedal Range" parameter. This is not logical but is works. ;)



    But this is very logical!
    Since it's not cool to read manuals, let me cite our Reference Manual Page 41: ;)


    "Volume pedal range
    This is a bipolar parameter. In the middle position, the volume pedal has no effect. When you set the range more to the left, you determine the minimum volume at heal-position, while the maximum volume at toe-position stays the same. At the minimum position, the pedal performs the swell from zero level, just as you would expect from an analog volume pedal. When you turn “Volume Pedal Range” to the left half, the volume pedal turns from an attenuation pedal into a booster pedal. Now, the heel stays at standard volume, and the toe-swell will give you a volume or gain boost. The maximum boost, at the top position of “Volume Pedal Range”, is +24 dB."


    This is how the volume pedal works and this is also how the Pedal Range works in the Wah Pedal Booster, where you use the Wah pedal instead of the Volume pedal.
    The Volume parameter in the Wah Pedal Booster is the same as in all Stomp effects. It is not really usefull in this effect, so I would recomment to leave it at zero (middle) position.


    CK

  • hello , I've been testig both solutions, I'm totally in love with the wha booster , it's a fantastic way to discover the incredible tone range on a single amp, from clean , crunchy to super lead just with a subtle amount of the foot press, mighty great feature M Kemper !!! :thumbsup:


    Thanks a lot guys for your explanations, I'll now need 1 more expression pedal.


    R.


    ... so reading the manual could save you some bugs. :P