In this experiment, i connected an audio signal to the RGB lines via a an inverter and a couple of other IC’s for some added fun, and using different combinations of connections, the audio is represented on the screen.

I wan’t really expecting much from this, in fact i didnt think it would work at all, however the results were quite impressive for such a crude circuit!

After playing arround with this, i’ve found out a few interesting things. Firstly, soldering a 15 pin D socket and mounting it to case is a pain in the ass, and secondly, if you strip the rgb content from the vga signal, you can replace it with what ever you want as long as the sync signals are intact.

This allows the monitor to be fooled into thinking the signals its being sent are from the same source as the sync and will pump out what ever you throw at it with in reason. So, with a few modifications to the circuit, i’ll be able to generate complex wave forms from the audio input to output over the RGB lines, and give the option to super impose them onto images from the original RGB inputs….

I ended up adding a couple of diodes to the sync cables as there were some issues with the monitor not being able to sync with the computer properly with some of the connections, and this seemed to solve most of the problems. There was no scientific reasoning behind using the diodes that i did, other than they were spare ones i had from before. Maybe something more specific would be better.

The whole point of this was to see how the RGB lines reacted to a raw audio input, and what connections need to be left alone, to allow stable operation of the circuit. In future experiments, i’ll know what “normal” audio reaction looks like, compared to new circuits i’m going to be playing with, and gives me a reference point to come back to.

Different audio frequencies create a line on a certain point of the screen. there are a few different combinations of effects here, and color switching controlled by activating the switches connecting the circuit to the RGB connections of the VGA output, so i can produce more than just red, green or blue images, but a few mixed colors as well. Maybe a color mixer could be incorporated into the final project… Although this thing is great fun already!!!!

I decided to house the whole thing in an old project box i had after building it on a bread board. Its a nightmare of wiring in there! Next up is to create an envelope follower circuit to see how this synth circuit reacts to control voltages, instead of a raw audio input. I’m going to try out a few different versions of the Dr. Quack circuit to see what results i get from each. More On that later.

there’s a whole lot of wiring in there!!! these hammond electricals boxes are really handy for these things, stompboxes and little noise synths, and are really sturdy too! this poor little sod ended up being used for a quick kick about in a venue after a gig as someone spilt a pint over the lighting desk and it died, but after drying out it was still alive, if a little scuffed arround the edges.  it just goes to show how solid these cases are, however he-who-shall-not-be-named still bears a scars from a failed flying volley… so perhaps a little too solid for that purpose.

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