MATRIXSYNTH: DIY laser turntable plays Morton Subotnick's "Silver Apples of the Moon"

Monday, May 25, 2009

DIY laser turntable plays Morton Subotnick's "Silver Apples of the Moon"

YouTube via EA78751. Buchla
"An experiment. Actually, the turntable isn't modified at all. The laser pointer beam is focused by a cheap lens, and reflects off the spinning vinyl. The grooves modulate the beam, and the modulations are picked up with a photodiode. Nothing is touching the top side of the record.

http://ericarcher.net/devices/lite2sound

thanks for watching"

4 comments:

Steamy Vicks5/25/09, 1:06 PM
That was just amazing - thanks for sharing this.
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Anonymous5/25/09, 5:01 PM
imagine if this technology was perfected. the fidelity of vinyl without the wear caused by repeated plays using a needle.
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nonymous5/26/09, 9:09 AM
Actually laser turntables have been commercially available since the '90s. They are fairly expensive, but have some advantages.
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alloy-tarakona3/12/26, 6:52 PM
I have no idea if this blog is still actively monitored, but I'm currently working on a similar project to what is described, and stumbled across this 17-year-old post. It looks like the video has since become unavailable (even tried the wayback machine to see if there was a working capture there, no dice. I see that the EA78751 channel is still around and active, at least as of 8 months ago, but any trace of the turntable experiment from 2009 seems to be lost, presumably due to copyright claims on the music.), which is unfortunate because I've found very few resources on using near-IR for record playback outside of the ELP, which I can only imagine was the "fairly expensive laser turntable available since the '90s" mentioned by other commenters here. As much as I'm interested in the ELP, I don't think I'll be spending 5 figures on it anytime soon, (because of course the price hasn't fallen whatsoever,) and in the meantime, I intend to DIY something comparable in quality. I don't know the exact amount of precision I would need from a laser+sensor for this project, but I figure the required precision can't be more than that of two strictly-focused low-power continuous-wave near-IR lasers mounted orthagonally to eachother at 45-degrees from vertical with high-sensitivity silicon avalanche photodiodes in linear mode. Don't know if there's any all-in-one distance sensor kits that would be able to complete these needs at a reasonable price? Most lasers have a focal spot that's way too wide, and a range that is way too far, but if I use an aspheric lens focusing to 18 microns or less, I should be able to focus both lasers on either wall of the record groove to differentiate vertical and horizontal modulation for stereo playback. I'm unsure of exactly what lens you were able to use, but it sounds like you had some success...? Assuming I go with a distance-sensor route, the lens will throw off the analog distance reported drastically, but the displacement is the only thing that matters in carrying the audio signal, and I reckon the warped sense of distance the laser attains from the lens will actually help in getting a clearer signal from the groove walls, since the tiny amounts of modulation in the groove will be picked up as larger changes in distance. I hear that near-IR is the safest laser to use on vinyl/shellac due to the materials reflection/absorption rates, but I don't have any hard numbers to be assured with. The audio signal wouldn't necessarily pass through the arduino, so the output sound will be completely analog.
If anyone sees this, thoughts / advice / technical knowledge would be appreciated, or even being told that I'm overcomplicating something and given a simpler alternative. And maybe, if my project succeeds and the audio quality is tight enough to be valuable, eventually I might try to start producing a more-affordable alternative to the ELP.
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