You’ll throw your back out playing this analog TV synth


While CRT televisions fall to the wayside as more people adopt flat-panel TVs, the abundance of unused sets gives hacker/artist [Kyle Evans] an unlimited number of analog canvases on which to project his vision. He recently wrote in to share his latest creation which he dubs “de/Rastra”.

The “CRT Performance Interface” as he calls it, is an old analog television which he hacked to display signals created by moving the TV around. Fitted with an array of force sensors, accelerometers, and switches, the display is dynamically generated by the movements of whomever happens to be holding the set.

Signals are sent wirelessly from his sensor array to an Atmel 328 microcontroller with the help of a pair of XBee radios, where they are analyzed and used to generate a series of audio streams. The signals are fed into a 400W amplifier before being inserted into the CRT’s yoke, and subsequently displayed on the screen.

We’re sure [Kyle] is probably trying to express a complex metaphor about man’s futile attempts to impose his control over technology with his project, but we think it simply looks cool.

Check out [Kyle’s] work for yourself in the video below and give us your take in the comments.

11 thoughts on “You’ll throw your back out playing this analog TV synth

  1. When I first saw it I thought it was creating sound by the movements of the user deforming a waveform shown on the screen by interfering with the CRT. As it stands, it’s basically a big controller for something else doing the synthesis.

    Looks damn cool anyway

    1. I don’t think it was due to mishaps.

      The electron beam intensity appears to be set constant, and relatively high. This is easiest, and necessary to give a nice bright trace when it’s scanning quickly.

      But when it’s scanning slowly (or not at all), all that energy is focused in a smaller area; which can be enough to burn the phosphor. That typically happens when there’s little or no input signal, which is why the burns are in the center of the screen.

      The phosphor used in oscilloscopes, where this happens regularly, seems to be more tolerant to that. TVs or monitors turned into oscilloscopes, however, are not very tolerant at all.

      A long time ago, I took an old IBM dumb terminal with a green screen, and wired the X/Y deflection coils to the left/right channels of my stereo through some power resistors. And had the same problem with phosphor burns around the center of the screen. The exact center of the screen was so burnt you couldn’t see the beam at all when it was there. It didn’t really detract from the display when operating, though.

      If you were to bother with solving this problem, you’d need to measure the deflection rate, and dynamically adjust the beam intensity. Slower deflection = less intensity.

      Great video, BTW. I watched it twice.

  2. Cool and freaky hack.
    But a 400 Watt amp? I think there is a mistake here (damn PMPO and its fake power measuring). I have made the same thing for years (controlling the yoke, not a synth) using only an LM386 as power amplifier.
    Also, about the ‘fakeness’ of the power of amplifiers: Once I saw PC speakers (yes, that little thing with terrible quality), that claimed to have 80W of power output…

    1. A cheap car booster perhaps. 12.5w oh that’s 400W, look we’ll sell more. Those ratings are like measuring the HP out of a car’s engine by crashing into a solid wall and quoting the liberated energy. Having done this TV-scope thing in 1970, I think a 386 is too small save for a battery-DC TV. 3-5w generally did it for a 19 inch TV. Make a scope with nuttn but the TV, sound-vertical, old vertical-new horizontal, old horzontal-junk deflection coil(kept switching power happy).

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