Castle Patching 002: Digital Sample and Hold



At the end of this exercise you should be able to *pixelate a digitized video source. This exercise expands upon the previous exercise; Castle Patching 001: Digitizing Luma Video Sources. I call this a digital sample and hold because like an analog sample and hold this will hold the 3-bit binary value at the D0-D2 inputs at the rising edge of an incoming clock signal until the next clock pulse comes in. The held value appears at the D0-D2 outputs.
Tools needed for this exercise are: Castle ADC, Castle DAC, Castle Clock VCO (or other VCO), Castle D Flip Flops, and a video source.

*I say pixelate, because the effect looks similar, but unlike pixels which are rectangular or square, this effect is on a per line basis. It also isn’t constrained to a global pixel clock, you can vary the clock at video rates and get unusual pixel geometry.

Take the patch from exercise 001, and instead of going from the ADC to the DAC, go from ADC outputs D0-D2 and put them in to the D0-D2 inputs of the D Flip Flops. Set the Castle Clock VCO to HI Range, and H sync. Set the frequency at its highest value to start. Take the output of the Clock VCO to the CLK input of the D Flip Flops. Take the D Flip Flop outputs D0-D2 in to the DAC D0-D2 inputs. The DAC output will go to your video output. Now have fun varying the Clock with CV inputs, or rearranging D0-D2 in any order. This completes the Castle Digital Sample and Hold patch.

This was probably the most exciting effect for me when I was first designing the Castle series. The idea of varying the size and shape of a pixel seemed so interesting, it would open up a completely new look beyond video games. Once I saw the effect come alive on screen I knew it would be something I would use time and again in my patches.

Patch picture: Clock with no modulation

Patch picture: Clock with modulation

DIY Questions:)