[sdiy] DIY Optical organs.

[Gene Stopp]

Holy moley this is a dangerous idea :) Talk about DIY. I can see that my
meetings this week are not going to be productive at all.

To me one of the fun things about DIY is building something and showing
somebody and having them say "I can't believe that you did that".

There was a time long ago when I read the .wav file header spec and wrote a
program (in QuickBasic fer heaven's sake) that read a .wav file and printed
a graph showing the waveform.

Overhead projector acetates print just fine in laser printers, and in Xerox
machines too for that matter. For a 6" drun you'd need at least 18" of
printout, meaning B sized drawing stock?

So all the pieces are there for the enterprising optigan/orchestron builder.
The problems I can see are trimming the loop points with multiple tracks per
transparency, and making sure that the fluctuating borders of the tracks
translate into the proper dark/light ratio in the photodetectors, hopefully
in a linear fashion. Then comes the drum construction - how do you join the
ends without an audible glitch?

Also remember that this mechanism was born of a time when memory was
expensive. But scanned EPROM etc. will obviously not sound the same, and
sound is what it's all about, innit?

Best Regards,

- Gene

-----Original Message-----
From: philicorda [mailto:philicordaNOOOSPAM at ntlworld.com]
Sent: Monday, January 27, 2003 12:53 PM
To: synth-diy at dropmix.xs4all.nl
Subject: [sdiy] DIY Optical organs.


Hi.
I'm a fan of the old optigan organs, and after despairing of finding one in
Wales, have decided to have a go at building one. The principle looks
straight forward, and I can code a little, so I think I can make something
similar using a computer to generate the tracks.

Rather than attempting to make circular records, I think it will be possible
to print the waveforms onto transparent acetate with a laser printer, and
roll the resulting sheet around a clear plastic tube about 6" in diameter.

I will then put the light source inside the tube, use a motor to turn it,
and use a single hand held photocell to select the tracks.
With a 1400 dpi printer I reackon I could get about 2 seconds of 7k
bandwidth with a pretty low amplitude resolution with about 10 tracks per
sheet.

Anyone tried laser printing waveforms onto acetate? I'm not expecting hi-fi
results. :)
I guess the only way is to try it, but I would be interested to see if
anyone else has had a go, and if they had any advice.
This list looks like a good place to ask!