bend wheel

edited August 2009 in WTPA1 Mods
Hey. Working on WTPA #2. I've got a bend-wheel salvaged off of an old midi controller. It's got a 50k pot on it... I'd like to temper that so that it's approximately the resistance of the "fine" knob -- but I want to keep the fine knob functional as well, so, 3 pots in series I guess. Any suggestions on how I should wire these, if I should add a resistor etc so that it works as it should? this is a v1 board, which calls for a 500k and a 10k, but I've seen reccommended elsewhere to use 10k and 1k as in the v1.01 boards.

comments? advice?

Comments

  • ah, yeah, I should also mention it does measure abt 25k in its default position -- and it seems to swing to abt. 25 ohms or so at the extremeties...
  • That might work. But it seems a bit crude, no? You might be better off using a proper midi pitch/mod wheel..
    If you used something like this: http://www.doepfer.de/we.htm you might even be able to use your existing wheel/s.
    I keep meaning to grab one of these boards so that I can make me a joystick midi controller.
  • 'tis a bit crude, yes. However, I can do things then like re-pitch the sample as I'm recording it, with the wheel, and do caveman-style pitch tweaks as well as using pitch wheel in MIDI mode... I had it laying around and it just seemed the perfect thing to outfit my sampler with. This one is going to be way more gritty than my first WTPA... -- I've even got plans to drive the sampler clock via an audio-to-logic conversion (not that I think this will work very well, but we'll see what comes of it...)

    Crude would be the object, methinks. I just want it to be scaled appropriately...
  • SMRL--
    You've got the right idea. With the bend-wheel in series with WTPA's conrols, though, and a resistor in parallel with your 50k pot, you'll find the taper gets really weird. Assuming the pitch-control pot is linear taper (which is a safe bet) and that you want 1k of possible change (like the fine control) then you'd use a 1k || 50k. This means that with the pitchwheel all the way "low" you'd have a 980 ohm resistor. With the pitchwheel centered, you'd have a 961 ohm resistor. Not a very big change. Most of the change would happen in a very small region near the end of the "bend up" direction.

    You may have better luck just putting the pitchbend pot across (in parallel with) the coarse pot. If the throw is too great for your liking, you could use a small series resistor. Play around with it until you get an adjustment range that you like.

    FWIW, it took tons of monkeying around with WTPA's controls to get tapers that I liked on those controls using standard parts. That's why the controls are "backwards" -- with high pitch all the way CCW -- because it allows me to use audio taper pots to help make the thing more controllable.

    Best,
    TB
  • OK, thanks for the info Todd -- I messed with this a bit.

    Not getting anything I like with the 50K, I found another pot I had that I could substitute that is 220 ohms. This, in series with the other two, worked out rather nicely, and I get abt. +/- 3 semitones.
    Not exactly ideal, I was hoping for a little more bend range than that, but it doesn't mess with the tapers, and is definitely getting some of the results i was looking for. Nice to make some wobbly samples when you fiddle with it in record mode...
  • Cool!
    Yeah, oftentimes with problems like that, the best way to solve them is to tinker. Like I said, it took fiddling to get the WTPA controls to "feel" right.
    Glad it worked out!
    Best,
    TB
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