Block diagram or description of analog abstract generators?

Hi,

I'm interested in learning more about analog abstract generators but I find it hard to get any good info!
I have acess to a lot of really complex modular synths and would like to use them to generate something beyond lissajous patterns, oscilloscope-like audio modulated saw-sweeps and such.
I have tried to inserts VCA:s and ringmods in the signal chain to make some aspects controllable but most of it looks sort of the same! Ways to make more geometric shapes, squares and maybe pointy objects would be cool and also know more about the building blocks for making the image rotate and other semi-3D operations.

I have an old geometric correction card attached to a pair of really old scanner drivers, I have been thinking of putting proper potentiometers on it and make it a module in my abstract modular, what do you think about that?

Any veteran laserists want to educate a poor victim of the digital generation? :)

OK

In the beginning there were open loop scanners and they were pretty cool. They couldn’t handle square waves, or even triangle waves, but Duh… If you sent them a sudden waveform jump they would do their best, and the ringing could be really interesting especially in dynamic waveforms. But the imagery of old was mostly done with several quadrature oscillators. A quadrature oscillator has two outputs. The second output is phase shifted 90 degrees to the first output. With two quadrature (sine/cosine) oscillators with the right frequencies and gains you get a square or a triangle or a star or a pentagon… you get the idea. A third oscillator lets you get more complex. Then throw in spirals, amplitude & frequency modulation, z axis rotation, etc. and you’re really beginning to have some fun. Oh, add polarity switch to invert one output of the quadrature oscilators...

Brian

P.S. The block diagram below is part of the Laserium patent from the 70's
Attachment 34381

Thanks, exactly the type of tips I was looking for!
I have a few sin/cos oscillators and ringmods/four quadrant modulators, I'll try to patch something up! When mixing the two oscillators, do I mix the two 0 degree signals and send to X and the 90 degree signals to Y?

I feel like I'm just peeking into another money/time pit here... :)

The 4QMMs are useful for building up z axis rotators. We used 2QMMs for spirals and other gains. ( i never really looked at Laserium's 2QMM circuit closely, but I assume the reason we built our own was to insure they went all the way to zero.) I can't visualize where ring modulators whould be particularly useful...

Below is a diagram of a basic quadrature oscillator control scheme.

Attachment 34391

Quote:

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Originally Posted by dar303

Thanks, exactly the type of tips I was looking for!
I have a few sin/cos oscillators and ringmods/four quadrant modulators, I'll try to patch something up! When mixing the two oscillators, do I mix the two 0 degree signals and send to X and the 90 degree signals to Y?

I feel like I'm just peeking into another money/time pit here... :)

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Thanks again! That is about how I ended up patching, two of these circuits into a mixer and then some LFO:s and slope generators to modulate different parameters. I used a Serge TKB keyboard/sequencer as a simple preset storage and a oscilloscope as a preview device.
I see that I can make a lot of cool stuff with the modulars but I think it would be much more practical to have dedicated hardware with better (DC coupled) VCA:s/2QMM's and DC coupled mixers with invert and offset controls but make a s many of the parameters as possible voltage controlled so the synth can be patched in when needed but keep the main signal path on dedicated hardware.

I made some progress, managed to get my new scanners up and running and a basic patch with two quadrature oscillators, a few DUSG's and some mixers plus a TKB as patchstorage.

I made a pentagram!
(It's a bit hard to focus the camera)
http://forumbilder.se/images/932201251302Pddc9.jpg

Here is the synth:
http://forumbilder.se/images/dd2201251615Pdade.jpg

And here is a lumia projector I built to go with the synth-kit.
It's a casio diode, 150mm discs from ornamental glass and it has a Flexmod P3 so I can control it and fade/strobe from the synth.
http://forumbilder.se/images/152201251725P0a45.jpg

A friend took this picture of the projections with his Hasselblad medium format camera, this is a low res preview:

http://forumbilder.se/images/871201214611P61ab.jpg


It was fun doing this "for real" at the Modern Museum in Stockholm, the artist that made the audio was very happy and we will probably do it again in a more developed way, might even pay me to build some custom modules!

If there is still any interest in this subject, I have a number of articles and schematics from the late '70's and early 80's. All of these projects were intended to make "abstracts" on an oscilloscope, but it wasn't much of a stretch to do laser art with them. In spite of the age of this stuff, a number of the parts, although obsolete, are still available, and many (multipliers) can be replaced with current production chips.
I'm hoping that other old analog dogs will share their stuff as well. I, for one, am looking for multiplier schemes that incorporate perspective control.

Hello,

I would be interested in anything you are willing to share.

ED

The stuff I have is currently in .jpg scans, and in some cases the articles are not complete. There is enough content that has survived that you'll get the idea.
I'll start converting the scans to .pdf files and start posting in a day or two. I'll also include notes based on my experience with the projects. Honestly, I could never be considered a "laserist" but I had a lot of fun with this stuff. My forte was beam shows- I worked for LaserMedia in the early '80's and toured internationally with several name acts.
The bug bit me again when I started reading about these cool little RGB diode bundles you can pick up for a few hundred dollars. Back when I was doing it professionally, the price for a white light laser of similar power could exceed $17,000.

Hello,

Awesome! That would be great.

If it is easier, I will convert your .jpg files for you. Just ask.

I am currently in the process of designing an analog console of my own.

ED

ED-
I'm toying with a "console" of my own, although I am leaning towards a modular design. PM your email address to me and I'll send you the stuff I have.
You are free to share, as all of this stuff is either public domain or un-copyrighted work.

Great idea to put this info out there for us! All inspiration is welcome, i'm considering a sort of hybrid analog system with parts of it in hardware and some in MAX/MSP and/or Supercollider software. I want hands on knob twiddling plus connection to my existing modular synths (Serge and Buchla) and some save/recall, algorithmic stuff and data visualization that these open software systems are good at...it just takes a lot of time and money! :)

OK- We are going to start posting some stuff you all will find interesting.
I am going to start uploading bits I am currently working on. Now, I use EAGLE for schematics and board layout.
I have no desire to learn a new layout editor, and I don't have the time or desire to scan and convert to pdf.
There is a free version of EAGLE available, so I suggest you get it. In the future, all of my schematics will be in EAGLE's .sch format.
J

Hello,

I would be happy to convert your EAGLE schematics and/or PCBs into PDFs if that helps.

ED

Anything new here? :)

Quote:

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Originally Posted by dar303

Hi,

I'm interested in learning more about analog abstract generators but I find it hard to get any good info!
I have acess to a lot of really complex modular synths and would like to use them to generate something beyond lissajous patterns, oscilloscope-like audio modulated saw-sweeps and such.
I have tried to inserts VCA:s and ringmods in the signal chain to make some aspects controllable but most of it looks sort of the same! Ways to make more geometric shapes, squares and maybe pointy objects would be cool and also know more about the building blocks for making the image rotate and other semi-3D operations.

I have an old geometric correction card attached to a pair of really old scanner drivers, I have been thinking of putting proper potentiometers on it and make it a module in my abstract modular, what do you think about that?

Any veteran laserists want to educate a poor victim of the digital generation? :)

---

I started out w/open loop galvos and analog generation of images way back. The XR2206 is a great little sine/triangle/square wave or ramp generator chip that can be voltage controlled and has built-in AM inputs. The chip is still available as is the 8038. The key to nice results is quadrature signals for X1Y1, summations (or multiplications or both) of more than one harmonically related frequencies X2Y2 (using PPL techniques) for each axis in the bandpass of the galvo (open or closed loop) with a harmonically related ratio range of 10:1 for base signals and in the range between 100:1 for amplitude modulation. For G115 or G120PD galvos I used 45 hz as the low end and 450 hz for the high end. Great things happen when X1, Y1 signals plus X2,Y2 have 1:1, 1:2, 1:3, 1:4, 2:3, 3:5, 7:10 frequency ratios, further excitement happens when amplitude modulating X1, Y1 while not modulating X2,Y2 or visa-versa.

As someone alluded to earlier, low frequency square waves (30-90 hz) on open loop galvos produces some great ringing affects at sharp transitions in the signal, especially when one axis frequency was very slightly adrift from the other axis frequency.

Here are some old pics of the type of results that give rise to harmonic geometries using summation and modulation or simply summation as in the last photo.

Attachment 46626Attachment 46627Attachment 46628Attachment 46629

I later applied what I had learned in to digitally controlling waveform generation via computer and married a combination of the two....but be certain of this....playing an "visual" analog frequency synthesizer in real-time to music is a blast.