CHA/V 2.0 User Guide

[this guide is a work in progress and will be updated regularly]

IMPORTANT: read the safety note at the end of this document before connecting things to the 3.5mm jacks

Congrats! If you made it here, you probably have a completed CHA/V that you’d like to test. Here’s a general overview of the controls:


To turn it on, plug in a 12v center-positive power supply. Center positive means that the sleeve of the jack is negative (in most cases it’s just ground) and the inside is the positive voltage. Anything above 500mA is more than adequate, and you can probably get away with even half of that.


dig through your box of old wall-warts and find a 12v one with this symbol, which means center positive.

If the power LED turns on and nothing starts smoking, you’re probably in business. If you have the CHA/V connected to a monitor with a VGA cable and you see color bars, you’ve passed the first test. Hit the background cycle button a few times and make sure it cycles though the colors. Hit the resolution cycle a few times and make sure it cycles through the resolutions.

All good? Cycle the background color to black.

Screen Shot 2019-11-27 at 12.59.02 PM.png

Before any of the oscillators can be used, we’ll have to put in some jumpers. It’s doubtful any of them will do much without jumpers.

First, let’s look at the vactrol headers on the VCOs:

Screen Shot 2019-11-27 at 1.03.09 PM.png

As-is, there’s no jumper, and because of that, the VCO circuit is not complete (it won’t do anything).

If you place a jumper connecting the [off] pin and the center-pin (the little triangle), the circuit will be complete, but the vactrol frequency modulation will be off. Here’s the off jumper position:

Screen Shot 2019-11-27 at 1.03.21 PM.png

If you want frequency modulation to be on, place a jumper connecting [on] and the center pin. Like so:

Screen Shot 2019-11-27 at 1.03.32 PM.png

In this position, the LDR will be inserted into the VCO circuit and it (in addition to the potentiometer) will change the frequency of the VCO. Once we get this fired up, if you wave your hands around over it, it will change the amount of light that the LDR sees, and in turn change the frequency (pitch). For now, put the vactrol headers of both VCOs in [off] position.

Ok, now we have to place jumpers on all the sync headers. Each oscillator has a sync header like the one pictured below. They are all identical.

The pins on the right (in the red box) are the sync inputs for each oscillator. There are 3 pins, but you should only connect one of them at a time. 

The pins along the left are:

horizontal video sync pulses from the VGA tester [H]

vertical sync pulses from the VGA tester [V]

ground [G] which allows the oscillator to free-run

In the picture below are some oscillators with jumpers in place:

OSC2 is synced to V

LFO2 is free-running (G)

VCO2 is synced to H

Initialize the CHA/V for some basic tests by setting the jumpers and switches like this:

This is the most basic configuration. The VCOs should make vertical lines, the OSCs should make horizontal lines, and the LFOs are ready to animate the VCOs.

Something counterintuitive about video oscillators is that horizontally synced oscillators make vertical lines, and vice versa. I didn’t make this up, it’s just the way it is.

In the above configuration, here are the basic patches to start with:

VCO1 > RED, GREEN or BLUE = Vertical red, green or blue lines

OSC1 > RED, GREEN or BLUE = Horizontal red, green or blue lines

See what you can come up with just by patching both VCOs and OSCs to RED, GREEN and BLUE and playing with the frequencies. Because each oscillator has multiple outputs, and each color has multiple inputs, you can experiment with sending one oscillator to multiple colors, multiple oscillators to one color, or any combination. Play with the coupling toggle switches to change the line thickness. Some combinations will work as expected, and others will have unexpected results, especially when lots of oscillators or colors are patched together.

For further experimentation, try cascading the sync through multiple oscillators, syncing a slow oscillator with a fast one, or a fast one with a slow one. All sorts of unexpected and interesting artifacts can happen when the sync starts getting weird. 

Patch VCO1 to a color. Turn the VCO1 vactrol [on]. If you cover the LDR of VCO1 with your hand, now you should see the frequency change. Try shining a light on it.

Set LFO1 to free-running (G) and set its switches to low/low. Now patch LFO1 into the FM pin on the VCO1 vactrol header. The LED should now be flashing and animating VCO1.

Change the frequencies of LFO1 and VCO1 and watch what happens.

Try V, H and G modes for VCO1 with all the different combinations for the toggle switches. Some will be orderly, and some will be chaotic. Also try syncing LFO1 to V or and see what happens. 


The 3.5mm JACKS are intended to get signals (audio, video, sync, control voltages, etc) in or out of the CHA/V. By default, they don’t do anything. In order for a jack to do anything, one or both of its corresponding pins on the JACK HEADER have to be connected to something.

Here’s how the JACK HEADERS work:

As the picture above illustrates, each jack has two pins on the header (the jack pins have a little picture of a jack next to them). Both pins for each jack are the same, and either can be used to patch a jack to something. 

The reason for the extra R, G, and B pins on the JACK HEADER is for the convenient patch below:

Also, more topics such as:


  • vactrol vca
  • background automation


  • creative applications of crosstalk
  • sync jitter
  • mixer sag
  • raw output
  • working with blanking
  • still higher resolution than composite video, lol


  • Although all of the oscillators have specialties, all of them are able to produce relatively high or low frequencies. Try playing to their strengths, and also AGAINST them. The rules were made to be broken.
  • Try leaving some jumpers off and see what happens when the oscillators “float”. You can also use your finger as a temporary jumper for sync or on the vactrol header.
  • Change the resolution if something is acting weird or not synching the way you want it to. This sometimes fixes things. It also sometimes clears up weirdness that occurs along the edges of the screen.
  • Change the background to white and all the colors will be inverted.