Another new crossover memeber

[Revmutt]

Hi, I'm yet another person coming from both the modular synth world, LZX video synth.

I have a fair amount of experience with oil wheel tech from the 70's. I have some light equipment and "DJ quality" lasers but they really can't blend with the oils and over heads.

I like the idea of doing stuff like audio reactive Oscilloscope stuff and abstracts, I don't have any great interest in using computers in this.

I saw this post and thought, yes a magic box and out of it comes light goodness:
http://www.photonlexicon.com/forums/...649#post258649

So are there options for someone with limited tech experience in this area to put together some sort of analog/ue psychedelic laser light show?

I have a bunch of noob questions but I'll start here.

Thanks,
Tommy

[colouredmirrorball]

Here is a thread that might interest you: http://www.photonlexicon.com/forums/...Analog-Console
Edit: good news, the OP of that thread made the design available for purchase! http://www.photonlexicon.com/forums/...874#post272874
I suggest waiting until he comes up with a design for on-board colour modulation, as currently you need your own source for colours. You could hook up 5 V to the colour inputs, but then they would be on all the time... (the colour board he provides is just able to dim each colour channel, nothing more.) Otherwise you'd need a computer after all!

Not many people use analog consoles anymore, but fortunately there are a few enthusiasts left, striving for a renaissance of the analog console.


Personally, I believe a computer + midi controller can do as much as an analog console (blasphemy!) while still having all the functionability of digital art.

[james]

It's LP records vs. CDs all over again!

James.

[Revmutt]

Thank you colouredmirrorball, that indeed looks like a possible place to start (assuming a vintage unit didn't pop up).

I still am at a bit of a loss in terms of things like interconnections. I get ILDA exists but for example when one buys a cheap RGB laser "animator" with that connection, does that mean if I am controlling it via that input it bypasses the birds, music notes and what have you that have been programmed into the unit.

Also is the above type of unit what one would buy if one was going to lets say wire up a synth to ILDA converter box?

I do appreciate the help.
Tommy

[james]

The 25 wire connector that looks like an old computer printer port is there for analog voltages to go straight to the inputs of the X, and Y galvos and the red, green and blue color modulation inputs of the projector.

The signals you put there are supposed to meet some criteria; like color signals go from zero to +5V and the galvo signals are set to a peek to peek, negative to positive voltage that gives you the scan angle or ultimate size of the image area you want to scan.

James.

[colouredmirrorball]

Yes, most projectors automatically detect if an ilda signal is present and disable the on-board effect library.

An Ilda signal is just an analog signal between 0 and 5 V on several channels. These signals are typically X, Y, R, G and B. Other signals can be present as well, such as X-, Y- (to balance the signal to eliminate noise), additional colour channels, a shutter, a Z channel (for whatever purpose), an Intensity channel (the sum of all colour channels), ...
The source can be either an analog console, an ADAT tape player, or a DAC connected to a computer.

Am I right if I think your project is hooking up a projector to an analog synth? I think that has been done before, but can't remember any threads at the moment... There has been some talk recently about this, I believe from The_Doctor who is also into synths.

The analog console posted above can alter incoming ILDA signals and generate its own signal as well (it even has a crossfader to toggle between the two sources). You don't necessarily need it to hook up your synth to your laser though, as your synth would be the signal source.

There are a few things you need to keep in mind when doing this though:
(1) Make sure your signal is between 0 and 5 volt. I believe this is standard, but better measure it anyway.
Edit: it could be the x and y signals are between -5 and 5 volt, not sure anymore (damn you James! :P)
Edit 2: looks like it's between -5 and 5 V, see here: http://www.laserist.org/StandardsDoc...finaldraft.pdf
(2) Galvos can't stand a lot of abuse. Your synthesizer is made to provide output to speakers who can easily handle frequencies up to 20 kHz. A galvo would long be dead before you reach this frequency... I'm not sure what the heighest safe frequency is, so I refer to the galvo specialists... This will also depend on your system. Do you have an idea what the point rate (in kilo-points per second) is that your scanners can handle?
(3) You are going to need more than two outputs from your synth. I'm not entirely familiar with real analog synths but I guess they just produce left and right... but ideally you need five signal sources for X, Y, R, G and B. That is if you want to modulate colours of course, if you aren't interested in that you can just mod it so it stays on all the time, or maybe use a fan with variable speed in the beam path.

[james]

Galvo signals are a kind of AC. They go as negative as they do positive with respect to ground. Color signals are supposed to be all positive.

Galvos are like an X, Y vector scope. Zero volts on either channel puts the beam in the center of the screen or the origin. Positive voltage moves the beam away from the origin in one direction and negative voltage moves it away in the other direction.

The signal you send to the galvos, be it digital or analog in origin, is going to be interpreted in real time as a set of Cartesian coordinates; X and Y.

James.

[Galvonaut]

I think that has been done before, but can't remember any threads at the moment... There has been some talk recently about this, I believe from The_Doctor who is also into synths.

I accidentally dragged a thread off topic(ish) regarding analogue synths here.

[colouredmirrorball]

Ahh, that's the thread I linked above. Didn't realize it was what I was looking for, LOL!
They mention 1500 Hz maximum frequency...

[james]

You can definitely use pure analog signals that come from synthesizers as galvo control signals.

One super simple example would be a 100Hz sine wave in one channel and the corresponding 100Hz cosine wave in the other channel.

Sine and Cosine are pretty much the same waveform but they are 90 degrees out of phase. The X and Y axis are 90 degrees apart.

So you get a circle.

Devices that are made for audio are usually capacitor decoupled at some point. Speakers do not translate absolute position. They translate CHANGE in position. If a signal moves from zero volts to some fixed voltage and stays there, that would do nothing but push out or pull in a speaker's voice coil and possibly burn it up. A DC offset on the output of an audio amp is considered a real problem.

This is not the case for galvos. Galvos do in fact respond to absolute voltage rather than change in voltage. So a DC offset in the signal will just move the galvo away from the origin and keep it there. That's a good thing.

A system with the ability to set and hold a DC offset is necessary to draw almost any kind of hand-drawn graphics. A system that is capacitor decoupled (speaker safe) will be naturally centered around the origin and cannot have many of the features that could be there if it was DC coupled.

James.