Bend Points

edited May 2009 in WTPA1 Mods
I installed an arduino with a custom shield that so far has a midi out port, a homeade vactrol and a 4066 switch IC. I also installed a bipolar power supply so I can add some filters and or other effects that require +- 9v. I am curious if anyone has had any luck poking around the circuit looking for bend points. I used one of the switches to create a psuedo ring mod. The idea was taken from little scale ( It sounds pretty cool. I tried it in a few different places, the best of which i think is the before the input. This way you can record a sample with the effect then overdub without the effect. This adds a distintlcy percussive element to a mix. With the remaining 3 switches on the IC I would like to use the arduino (via midi in) to trigger differemt bends

The vactrol is controlled by an the arduino (lfo). It is pretty cusomizable (speed, wave type, pwm, and prolly more). I have thus far just used to to control the clock and in place of one of the r2r bits. sounds ok but I am looking for a better application for this. I had a ad5206 that I sampled so i was also thinking of using a rotary encoder and digital pots instead of the knobs on board. I think I am getting a little ahead of thing at a time -

anyone had any luck with some bends?


  • i managed to get some very cool memory corruption going the other night by touching legs on the HS of the memory chip. Wasn't able to repeat it though - kept resetting the board and I ended up getting a track going so bending is on hold for a while. there's def potential in that area though.
  • shame the pins are so bloody small!
  • I had a question and I wasn't quite sure where to post it:

    I have an old Yamaha RX17 drum machine and I've seen a few bent versions of it floating around out there on the interweb. Is it possible to have my Party powered off of the same power supply the RX17 has? I'm planning on eventually housing them in the same case so you could see how this would be useful.
    This is my first electronics project and I'm very excited but i'm about green to this as you can get.
  • depends on the PSU. As long as it is a DC supply between 8-15V DC it will be fine. The power is regulated on the board so technically you could use something up to 30V DC but all that extra voltage will make the vreg VERY hot so ideally, something 9 or 12V is ideal.
  • The 7805 is cool up to 30v, but the input electrolytic is only rated up to 16v. But yeah, Altitude is right, it's no problem to use the same supply if it's in the voltage range AND if it can source enough current. WTPA draws something like 200-300 mA, so if that plus the draw of the RX17 is less than the maximum current for the supply, then it's fine.

    Technically, WTPA can also run off another circuit's regulated supply -- if the other circuit has a regulated 5vdc output you can hook it up to WTPA's RegVcc port, but mostly that port was meant to power other stuff.
  • edited July 2009
    mobith, use the vias connected to the pins - the tiny holes around the board. Stick your wires into them :) although my WTPA is still in slight disrepair I've found some grimy bends.
  • Hi -

    I am currently looking for an option to switch on certain bends I have found / will find. These are the type of switches to get, right ( its an SPDT on / on) ?! Please advise.

    If I remember correctly my atari punk console deluxe from get lofi uses the same switch to turn on the lightsensor...
  • If you are just opening and closing a connection between two points, an SPST switch will work fine and be cheaper. The switch you linked to would be fine also.

    A switch connects the pole(s) to the throw(s). SPDT means "Single Pole Dual Throw". So the switch you linked to would toggle the POLE connection between the two THROWS.
    You can have many many different types of combinations of poles and throws, but SPST and SPDT are the most common.

    "on / on" means that the switch flips between these two states.
    "ON / (ON)" would indicate a momentary connection in one position -- the switch would return to the other position when you weren't actuating.
    "On - Off - On" would indicate that there is a center position on the switch where the pole was connected to NEITHER throw.

    Hope this helps!

    ps -- as usual the wikipedia article is great:
  • it helps a lot indeed! thanks for your time, todd!
  • @blue_lu: Can you share some of the bend points you have found?
  • edited August 2009

    I will gladly do so. I am at my parents place right now, going into holidays right after this. So it I will not be online for 3 weeks. I haven't written them down, but I somewhat remembered the good ones. To give you an exact description though, I need to sit at my wtpa and write it down. I will do that once I get back.
    I just remember the good kind of effects I have found so far:
    - distortion: is almost everywhere, different intensities as well as different voiced as well
    - short echo: this happens around the s-ram! it is clock-dependent: the faster the clock the shorter the echo
    - HighPass Filter: Happens when you connect to resistors at the 4 volume pots (try the bend point between r15 and r16 as the "base" - then connect to each of the bend points below r16. I think that's where I found it)
    - glitch effects: around the ram, if I remember correctly
    - played notes: I will have to retry that. I found a couple of notes that can be "played" over the sample - I don't know if these are clock dependent and change pitch if you turn up the clock of the sample.

    Right now I don't really remember much of the bend points... I will post, once I am back at my desk (roughly three weeks - three weeks without wtpa *sigh*)!
    Later, Lu
  • HP Filter, eh? Now you say these are located volume pots, does that mean the filter sweep will occur at the same time/range the knob is turned? can a put be put in place before the filter?! AWESOME find, my friend.
  • Y'know, so far all y'all badass circuitbenders have been pretty tight-lipped about bends you've found...

    As you know, I am too busy dusting my taxidermied safari trophies and sipping Moet with my pinky extended to trouble myself with looking for circuitbends.
    Am I going to have to have a contest and give away free stuff to the people who provide the most comprehensive list of cool bends?
    Is that what you all are trying to do?

    ab uno disce omnes,

    T.M Foxworthy
  • aaahhh... todd. I will share - I swear!!! I just have my wtpa not handy right now ( for the next three weeks - I am visiting sweden). I will post when I get back. I got so much inspiration and help on these boards just by reading - I will try to give something back. even if it is just my crappy bends. again - three weeks and counting...
  • donsandwhich:

    no, as far as I remember the high pass filter is fixed. it sound like a radio / very mid emphased eq. try the points I described - there are only three possibilties...
  • edited August 2009
    Ok so since Todd was nice enough to build this, I guess I will be nice enough to share what I have found so far (I finished my WTPA yesterday). I am not super knowledgeable on circuity so you do this at your own risk, with that being said let's get on to the good stuff. So far I have just been doing simple ground to pin probing and the best chip is the surface mount chip, as it's bends seem to be the most stable. The 74LS373N chips is another place to find most of these bends but for whatever reason they seem less stable and seem to reboot the WTPA more often, not sure why (as noted later some chips are worse than others). First I will go through the surface mount chip bends:

    (For clarification - When I count pins I start on the top left as 1 count down to the bottom then continue on the top right and go down again)

    1. nothing
    2. ring mod
    3. ring mod
    4. ring mod
    5. ring mod
    6. nothing
    7. distortion
    8. distortion
    9. Avoid - Reboot
    10. nothing
    11. stutter
    12. stutter
    13. sample access*
    14. distortion (digital)
    15. distortion (digital)
    16. distortion (digital)
    17. distortion (digital)
    18. distortion (digital)
    19. nothing
    20. nothing
    21. random playback**
    22. random playback**
    23. random playback
    24. Avoid - Reboot
    25. random playback + decimate
    26. random playback + distortion
    27. nothing
    28. Avoid - Reboot
    29. random playback + ring mod
    30. random playback + ring mod
    31. random playback
    32. random playback
    33. stutter
    34. stutter
    35. stutter
    36. nothing

    Note: The random playback is kind of like the lower setting on the granular effect and some of those pins seemed to reset the WTPA
    * This usually just added in a tone from the ground but when connected to other pins it adds interesting clicks and pops. So be aware it is PERMANENT DESTRUCTIVE EDITING to your sample!
    ** This only seemed to work on the second half of the sample playback.

    Now on to the 74LS373N chips there is 4 of them and they each have 20 pins. I counted the pins the same as above, and I numbered the chips from left to right:
    1- left chip (IC4)
    2- higher chip on left of the board (IC3) (the right side of this one is bad for reboots)
    3- lower chip on left of the board (IC2)
    4- right chip (IC8) (this one was the worse for reboots)

    I didn't document these as well with a description (more of these reboot the WTPA which gets annoying after the 30th time!) but here is a breakdown of which had bends:

    1-IC4 2-IC3 3-IC2 4-IC8
    1. no no no no
    2. no yes no no
    3. yes yes yes yes
    4. yes yes yes yes
    5. no yes yes ?
    6. no yes yes ?
    7. yes yes yes ?
    8. yes yes yes ?
    9. yes ? yes ?
    10. no no no no
    11. X X X X (Power I think)
    12. yes no yes no
    13. yes no yes yes
    14. yes yes yes yes
    15. yes no yes ?
    16. yes no yes ?
    17. yes yes yes yes
    18. yes yes yes yes
    19. yes no yes no
    20. no no no no

    Well there you go, hope it's a start for your bending freaks. These are just my simple finds and none of them have broke it yet, but just remember your mileage may vary! Mmmm can't wait to drink some coffee out of my new narrat1ve mug!
  • edited August 2009
    Oops the things didn't lay out right, I will try to correct that later. Sorry no time to right now!
  • Binary, you're the bees knees!
  • edited September 2009
    Haha, I just do what I can! I just finished soldering my bend points, yay for me! So just to let everyone know on all but two of the pins you can follow the trace from the ram to the little holes and solder there. The only ones that don't have these are pins 4 and 5 on the ram, but these bends can be found on pins 9 and 19 on the 74LS373N chip marked as 3 (IC2). Just for clarification those are the second to last pins on either side on that chip and I just soldered the wires to the socket pins. I went for 24 points and a 25th to ground, then I ran these wires to a D-sub connector to hook to a breakout box. I may build my patch bay next week as I have had a few too many long nights with this bad boy! I will post pictures when I have the time.

    Edit: The other weird pin is 35, the trace for that one comes out from under the bottom of the ram.
  • Ok, I only have two bends documented on my digital cam so far - the bends are the blue wires! Simply connect them with an on on switch. Here are the pics

    This one was a resonance / ringmod bend

    And this is the stutter, I think(!)

    I will post the rest soon.
  • @Blue_lu: Are those two bends in the pic or just one bend that requires two points to be connected together?
  • sorry for the confusion _ each pic represents one bend (two bends in total).
  • edited January 2010
    So I assembled my second WTPA V1.0 board, and added some bends to it, here are the results, you can get some cools sounds for sure. There are 4 bends, they start at 0:39sec and I run each one for 10 secs individually, then after that I mix them up, you can get some cool robotic sounds, I call it transformer mode LOL

    Here's the mp3:

    Also the audio is cleaner on this one compared to the first WTPA I built.
  • What changes did you make from the first one to get cleaner audio?
  • Not really sure, I made the same changes I made the first one. I upped a few caps on the audio out, took the 10uf to 47uf and took the .1uf to 10uf. I also jumped r13 (I believe) instead of having the 1Mohm resistor in. Remember this is a 1.0 board though, I posted all the changes in this thread also: but I jumped R13.

    I also used a different brand of potentiometers, maybe there better quality?
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