The Kraakdoos — Musical Abuser of an Ancient OpAmp

A friend from the newly founded Yeovil Hackerspace introduced me to a device known as “The Kraakdoos” or cracklebox.

The cracklebox is an early electronic instrument produced by STEIM in the 1970s. The instrument consists of a single PCB with a number of copper pads exposed on one side. The player touches the pads and the instrument emits… sounds which can perhaps best be described as squeeze and squeals.

While the cracklebox was original sold as a complete instrument, the device has been reverse engineered, and the schematic documented. What lies inside is quite fascinating.

The heart of the cracklebox is an ancient opamp, the LM709. The LM709 is the predecessor to the famous LM741. Unlike the 741 the 709 had no internal frequency compensation. Frequency compensation is used to intentionally limit the bandwidth of an opamp. As input frequency increases, the phase shift of the opamp also increases. This can result in undesirable oscillation, as the feedback network forms an unintentional phase-shift oscillator.

Most modern opamps have internal frequency compensation, but the 709 doesn’t. Let’s see how this is used in the cracklebox:

krackdoos_schRather than using the frequency compensation pins as intended the cracklebox just routes them out to pads. In fact the cracklebox routes almost all the pins on the opamp out to pads, including the inverting and non-inverting inputs. A single 1MOhm feedback resistor is used in a non-inverting configuration. However reports suggest the instrument can work without a feedback resistor at all!

Continue reading “The Kraakdoos — Musical Abuser of an Ancient OpAmp”

Hackaday Prize Entry: Ultimate Circuitbending

Circuit bending is the process of taking a small electronic toy or musical instrument, soldering wires to pads on the PCB, and hoping the sounds it produces will be cool. It’s not a science by any means, and any good, weird sounds you’ll get out of a Speak ‘N Spell or old MIDI keyboard are made entirely by accident or hours and hours of experimentation.

[Alpha Charlie]’s entry for the Hackaday Prize is the most technologically advanced circuit bending you’ll ever see. He’s using an old digital beat box, the Roland TR-626, with computer-controlled wires between random pads on the PCB.

Until now, you could tell how technically adept a circuit bender was simply by how many switches were on the circuit-bent instrument. [Alpha Charlie] doesn’t need switches. Instead, he’s using a few crosspoint switch ICs to connect different pins and pads on the TR-626’s PCB with an Arduino. All of this is controlled by a touchscreen display, and experimenting with the circuit is as simple as pushing a few buttons. Each ‘bend’ is computer controlled, and can be saved and recalled at will.

Of course, circuit bending doesn’t do anyone any good if it sounds like crap. [Alpha Charlie] doesn’t have to worry there. In the video below, he’s getting some very unique sounds that sound like a choir of angels to dorks like myself that listen to Nintendo music.

Continue reading “Hackaday Prize Entry: Ultimate Circuitbending”

Digitally Controlled Circuit Bending

Circuit bending doesn’t get a lot of respect around some parts of the Internet we frequent, but there is certainly an artistry to it. Case in point is the most incredible circuit bending we’ve ever seen. Yes, it’s soldering wires to seemingly random points on a PCB, but these bend points are digitally controlled, allowing a drum machine to transform between bent crunchiness and a classic 1980s drum machine with just a few presses of a touch screen controller.

All circuit bending must begin with an interesting piece of equipment and for this project, [Charles], the creator of this masterpiece of circuit bending, is using a Roland TR-626, a slightly more modern version of the TR-606, the percussive counterpart of the infamous TB-303. The circuit is bent in the classical fashion – tying signals on the PCB to ground, VCC, or other signals on the board. [Charles] then out does everyone else by connecting these wires to 384 analog switches controlled by an Arduino Mega. Also on the Arduino is a touch screen, and with a slick UI, this old drum machine can be bent digitally, no vast array of toggle switches required.

[Charles] has put up a few videos going over the construction, capabilities, and sound of this touch screen, circuit bent drum machine. It’s an amazing piece of work, and something that raises the bar for every circuit bending mod from this point on.

Thanks [oxygen_addiction] and [Kroaton] for sending this one in.

Continue reading “Digitally Controlled Circuit Bending”

VISUALIST – a hardware visual effects synthesizer

[Berto] wrote in to tell us about the visual effects synthesizer he built. It works as a pass-through for a video signal, rendering crisp clean images into a more psychedelic flavor like the one seen above. On the one hand this does a dishonor to the high-quality video devices we carry around in our pockets these days. On the other hand it will make some really interesting background video at a party or at your local dance club.

This is not a filter for a PC, or an FPGA-based processing system. A set of analog parts alter the incoming composite video (NTSC or PAL formats) and pipes the result to a television or projector. [Berto] included controls to alter the effects. They’re mounted on a panel and everything is given a home inside of a handy carrying case. Check out the video clip after the break to get a better idea of the video manipulations this things can pull off.

Continue reading “VISUALIST – a hardware visual effects synthesizer”

Hackaday Links: April 11, 2012

This hurts our head

You know you can ‘freeze’ drops of water in mid-air by flashing a LED at the right time, right? Well, according to this video you don’t even need a strobing light; just use the frame rate of the camera. Much cooler if you don’t know how it works, in our humble opinion.

Now do Junkyard Wars!

[James Cameron] and [Mark Burnett] (the guy who created Survivor) are bringing Battlebots back to the Discovery Channel. The new show is called Robogeddon and calls upon the current talent in the fighting robot world. Our prediction? Someone is going to build an amazing piece of art that will be completely destroyed in the first round; a wedge with wheels will take the championship.

A steam engine made out of rocks

[Hansmeevis] just spent 230 hours hand carving a steam engine out of gems. It’s called “Dragon’s Breath” and it’s an amazing piece of work: the cylinder is carved out of quartz, while the flywheel, mount, and base are carved out of jasper, onyx, zugalite, and other semi precious gems. Amazing artistry and it works.

Don’t lose a finger on all that science over there

[Dr. W] is a science teacher in Saint-Louis, France. Next year, his students will be learning about reaction propulsion and impulse conservation. To demonstrate these properties, [Dr. W] hacked up an old vacuum cleaner in to a jet engine and built a Pitot tube to measure the 140 km/h wind speed. Google translation.

Circuit bending a Sega Saturn

Making cool glitched-up graphics from Ataris and Nintendos is old hat, but not much has been done with circuit bending slightly more modern consoles. [big pauper] found his old Sega Saturn in his grandma’s attic and wondered what secrets this forgotten box held. It turns out he can make some pretty cool sounds and even cooler glitched out graphics. The pic above is from Virtua Fighter; done correctly these glitched low-polygon graphics could easily find themselves in a very stylistic indie game.

Music synthesized from the Game of Life


[vtol] has built a very elaborate system of electronic sound machines, which can be patched together in various ways in order to create all sorts of sounds and sound effects. The modules range from simple noise synthesizers to pitch shifters, sequencers, and effects processors. The most recent addition to his synthesizer system is a matrix sequencer named 2112, which focuses on generating random sounds from a very familiar mechanism.

The sequencer simulates Conway’s Game of Life, representing the colony movements in beeps and buzzes, creating a nearly infinite array of random sound effects. Using firmware from the Game of Life board by Ladyada, the sequencer generates different sound patterns based upon the number of colonies on the board. The output varies according to the shapes and proximity of the organisms to one another. Since it is part of his already modular system, the 2112 board can be combined with any number of his other sound generators and effects machines to make all sorts of circuit bent music.

Keep reading to check out the trio of videos below demonstrating the Game of Life board in action.

Continue reading “Music synthesized from the Game of Life”

Long arms required, electronic trombone

Sadly, the video above is the only information we were able to find on the “Double Slide Controller” trombone, built by composer Tomás Henriques. As well as, the instrument took first place in the Georgia Tech Center Guthman Musical Instruments Competition. Right in front of a Bluetooth bow for violins, and a circuit bending group from New York, and…wait; it beat out our favorite modified didgeridoo? Better luck next year.