Wednesday, January 23, 2008

Exploratory composite video noise synthesis

By piggy backing a two-bit DAC signal of the correct voltage on a completely black composite video signal, a simple exploratory composite video noise synthesiser can be constructed. Each of the images below is of a relatively stable state that can be found by turning the two pots.


Anonymous said...

I love your Exploratory composite video noise synthesis

is there a schematic available? what chip did you use for the D2a conversion?

i would love to make one (i have made ALL the fun with sea moss circuits)


subjectivity at hot mail dot com

Sebastian Tomczak said...

Hi there,
Cheers for the comment.

Basically, there is no chip that actually "does" the DAC.

All it is is two really fast oscillators built from a 74HC14 IC, with relatively small value ceramic caps and 10 or 50k pots.

Both of the oscillators form a two-bit DAC together. The low bit has a 1kΩ resistor and the high bit has a 330Ω resistor.

Additionally there is a 75 ohm resistor between earth and signal output.

Then its just a matter tuning the oscillators until you get some stable artifacts!

You can see the DAC resistance circuit here:

But instead of coming from Arduino pin 6 and 7, the two bits are coming from the 74hc14.