Step 2: The Circuit
Feel free to experiment with component values, but be aware that some of the values are rather specific, and changing them too much will adversely affect the operation of the circuit, potentially causing damage to components on the board or to devices connected to it.
All of the "external" controls - the ones that are used by the musician on a regular basis - are connected to the board using header connectors. This is optional, but I do recommend it since it makes troubleshooting and assembly easier (or possible, in some places!)
At first I was going to design my own power supply, but then I found a nifty pre-built power supply with exactly the specs I needed. It's a little pricey at $60 but I think it was worth it. Who wants to mess about on something trivial like the power supply? The Prism was designed to run on +15, -15 and +5V, though it may work just fine on +12, -12 and +5V, which means you could use a modified computer power supply. I haven't tried it though, but it certainly wouldn't harm the circuit.