Finished Pieces

Speak&Spell Bending

    The “HOLD” feature in the schematic above takes some fine tuning to get right. There are parallel resistors and buffer resistors, a pot and a switch. The values of the potentiometer and resistors for this feature are meant for reference only. I’ve found that they often need to be tweaked from model to model. If you are new to bending, don’t bother with the adjustment and the trim resistors, just wire the switch to the two “hold” points on the main board. The same goes for the “LOOP” feature. The adjustment lets you fade between loop and glitch effects, but it takes some tweaking. It’s much easier to take out the pot and resistor and just wire in the switch.



    33 Responses to “Speak&Spell Bending”

    • 1

      GetLoFi - “The day the machine which is bent” » Casper Electronics Interview said:
      December 13th, 2006 at 12:31am #

      […] Pete Edwards of Casper Electronics has recently posted a ton of new material to his site including a segment recorded by a Swedish TV show SHOWROOM. The video is packed with great footage of Pete’s workshop along with an explanation of what circuit bending is and some actual Speak and Spell bending. Pete also posted an intense collection of Speak and Spell diagrams and an authentic schematic of a Speak and Spell circuit in the Speak and X circuit bending section. The Barbie Karaoke machine bending page now also features more in depth documentation. Thanks for sharing the info Pete. […]

    • 2

      Awesome Circuit Bending Illustrations at Synthtopia said:
      March 7th, 2008 at 12:11am #

      […] Casper Electronics has the stuff on circuit bending. […]

    • 3

      * Casper Electronics » Archive » New Speak&Spell schematic said:
      March 17th, 2009 at 2:03pm #

      […] read the notes for this schematic on the Speak&Spell bending page before attempting the modification illustrated […]

    • 4

      Gristleasmo ! « ASMO said:
      January 21st, 2010 at 10:01am #

      […] circuit is based on Peter Edwards’ Speak and Spell LFO schematic at, I made a few changes to the design to suit the Gristleism. I built the mod over the Christmas […]

    • 5

      jknppp said:
      April 14th, 2010 at 3:15am #

      hello 🙂
      Is there is a way to create custom expansion modules for speak n spell ? with arduino or something else ?

    • 6

      frank said:
      April 26th, 2010 at 10:41pm #

      do you have schematics on speak and math? or are they the same? how can i get a relay sequence?

    • 7

      casper said:
      May 1st, 2010 at 3:46pm #

      That’s a good question. I’ve never given the expansion modules too much thought. ie, what they or how they work. Theoretically it would be possible to make modules that trigger custom words or phrases… I think. You’d have to look into the communication protocol for the S&S. Sorry I can’t be more help. COol idea though!

    • 8

      casper said:
      May 1st, 2010 at 3:50pm #

      The Speak&Spell and Speak&Math are the same inside. The only differences are the touch panel and what they are programmed to say. The general design of the circuit board went through a few revisions over the 30 years or so the S&S was in production. So you may see a difference between the circuit board of a SPell and a Math, but that has more to do with the revision # than the differences between a Math & Spell.

    • 9

      macy said:
      June 1st, 2010 at 5:31pm #

      love your stuff.

      Are the schematics similar with the speak and read?

      And what exactly does the joystick add control?

    • 10

      jknppp said:
      July 27th, 2010 at 9:25am #

      @Casper, thank you for answering 🙂 but I think it should take me half my life to learn this kind of protocol, I’m too lazy 😉 anyway thank you very much for the great material you put online !! hope to have the time to see you next time you come to france !!!!!!

    • 11

      Dan Gray said:
      July 27th, 2010 at 6:00pm #

      What Kind of joystick were you using in your Speak bend? I thought most Computer joysticks used DB-15 connectors. Is it for a Game controller type (switch instead of pot) controller? If for a potentiometer controller, how would the DB-9 pinouts correlate to a standard DB-15?


    • 12

      casper said:
      August 7th, 2010 at 9:20pm #

      @ Dan Gray:
      I used an old Atari controller. It is the switch kind rather than the pot kind. The pin out is specific to the joystick you use.

    • 13

      casper said:
      August 7th, 2010 at 9:22pm #

      @Macy: the schematics for the speak&read, math and spell are all the same. The joy stick is just a series of on/off switches. I used it to trigger random words, glitches and a “hold” effect

    • 14

      POE said:
      September 21st, 2010 at 5:36am #

      Dear Casper,

      I just came across my first affordable S&S and have set about bending it. Thanks to you and your site.

      I was looking around for stuff and came across these 8$ joysticks that I think are mountable on the S&S.!?

      They don’t come with any information. Looks like they are arcade game replacements. I was thinking about ordering one. You have any words of wisdom regarding these?

      (and check out the multicade board.)


    • 15

      POE said:
      September 21st, 2010 at 5:53am #

      Can I hack the thumb wheel on a PS2 controller an mount it in S&S? Thought I would ask before I destroy one.

    • 16

      FaKe_ said:
      October 6th, 2010 at 11:34pm #

      Hey Casper–

      Just wondering how I can make the LED on the “Speak&Spell LFO” fade out instead of just a sharp off?


    • 17

      ALT said:
      March 12th, 2012 at 3:38pm #

      Are there any pictures of the underside of the keyboard? I was drilling to mount some pots and I’m pretty sure I cut some connections. Just wondering if there are any tracks that extend below the layout of the buttons? I dont want to rip of the button panel unless its neccesary. Basically I need to figure out if i can replace the buttons with momentary buttons.

    • 18

      Scrubber said:
      July 15th, 2012 at 8:55am #

      sweeet! thanks for these, love the drawings too! now both my S&S and S&M are fully pimped up! got speccy joystick going on one also! could do with some MIDI action on them but they are all discontinued now 🙁 think there is an DIY arduino version, might be worth looking into!

    • 19

      casper said:
      July 15th, 2012 at 10:12am #

      @ ALT. I should post some pics. There ARE tracks that extend below the buttons. There’s a strip about 1.5″ wide that runs right down the middle. Replacing the buttons with momentaries is relatively easy. It’s just a matter of figuring out the pattern on the connection strip (horizontal row of pins in the middle of the S&S circuit board). A little trial and error will get you there.

    • 20

      dj gocue said:
      October 7th, 2012 at 10:01pm #

      i just wanted to say thank you:D i finished your LFO for speak and spell
      and i love it 😀 i use the bent speaks for making rhythms for turntable drumming
      thanks again for your site bro
      DJ GOCUE

    • 21

      casper said:
      October 23rd, 2012 at 8:10am #

      @DJ gocue. I’m glad it worked out! Please post links to some recordings!

    • 22

      Daan said:
      January 4th, 2013 at 7:38am #


      I’m really new to circuit bending. I just bought the membrane keyboard S&S and am fiddling around with it. I’d really like to put a pitch shifter in but can’t really figure out the schematics on this page :/ Could anyone help me out here? I have various pot. meters I could use. Was hoping I could just hook that up to two points in the circuit board..


    • 23

      casper said:
      January 13th, 2013 at 6:01pm #

      Hi Daan:
      Look at this schematic:
      The point labeled “C”. This is the pitch base point. COnnect this to the center leg of a 100k potentiometer. Next connect the right leg of the pot to various points on the board. You will eventually find a point on the board that makes the pitch higher when you turn the knob. NEXT connect the left leg of the pot to various points on the board until you find a point that makes the pitch go down. Now you will be able to make the pitch go up and down by turning the knob.

    • 24

      Max said:
      April 2nd, 2013 at 9:03pm #

      I was wondering if you know of anywhere/anyone who has schematics/diagrams for the older pushbutton version of the S+S… So far, I’ve found 2 images and they have bend points all over them, and I’m looking for something clean…

    • 25

      Dakky said:
      April 10th, 2013 at 8:08am #

      I have a first edition speak and spell, with the plastic buttons, and I’ve noticed the circuitry is slightly moved around, could you give a reference or something for the C1 Edition with the changed pins? I realize the chip pinouts are the same, but other stuff seems to be moved as well. Thanks

    • 26

      Joel Saunders said:
      July 4th, 2013 at 5:45am #

      in the LFO picture should the – terminal of the 100nF capacitor connect to ‘B’ (ground) not ‘A’ the + terminal.

      I’ve built it. My LED is flashing beautifully, but the ‘Shape’ and ‘Depth’ knobs dont seem to work properly.

    • 27

      Jason said:
      July 23rd, 2013 at 8:43am #

      I also have an original speak. I am trying to use the lfo schematic provided. Everything is working ok but it only seems to effect the lower range of the pitch. I have tried all the other pitch spots with the same effect. Any ideas? Thanks

    • 28

      casper said:
      August 1st, 2013 at 1:47pm #

      @ Jason. Do you have a pitch potentiometer installed? This can effect the range of the LFO. Try turning the pitch down and then apply the LFO.

    • 29

      casper said:
      August 1st, 2013 at 1:56pm #

      @ Joel. The cap is drawn correctly and the circuit does work… although now that I look at this several year later, Im not sure why it is the way it is.

    • 30

      Jason said:
      August 19th, 2013 at 3:47pm #

      Hello again, got the lfo working beautifully. Awesome indeed! So I sat out to add a 4017 step sequencer to my project and have ran into another problem. The sequencer now only seems to effect the registers. I use a 555 to clock the 4017. I have the out put of the 4017 going to 8-10k pots bussed to a 100k. When I add the out put of the sequencer to the pitch point it has a small effective range. I can’t get it to step from a high pitch to a low. It only seems to effect the normal pitch and below. I have tried using all the way up to 1m pots to no avail. Any thoughts?

    • 31

      Jason said:
      August 19th, 2013 at 3:49pm #

      ^ meant to say it only effects the lower registers^

    • 32

      quentin said:
      November 18th, 2013 at 9:32am #

      Hey Peter hello!
      I was wondering if you did some experiment on the speak and read, because I’ve got one in a really good shape just with me and I really want to modify it to integrate these sounds in my setup, but I don’t find any tutorial bout this one! I heard that it’s circuit doesn’t really react like the S&S. What are your advices on it? I do not want to break it but I can’t wait to dig inside. I really needs infos…


    • 33

      Phil said:
      December 27th, 2014 at 4:43am #

      I want to add CV to my Speak and series, Where on the circuit should the + point be added? I have just fixed the power board and don’t really want to mess it up again.

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