My goal for this project was to capture the 2A03 sound, and then add features to make the chip more friendly to musicians. Call my program an enhanced "re-implementation" of the 2A03. It is an 2A03 freed from the limitations of the original hardware. The core 2A03 "sound" however is preserved and faithfully reproduced.
At it's core, the 2A03 contains 4 sound generation circuits:
- triangle generator
- 2 square wave generators (each having a slightly different sweep algorithm)
- noise generator
To ensure that the sound was authentic I first read various online documents describing detailed operation of the chip. I found Brad Taylor's online technical reference document to be an invaluable source of information for this project. Using this information I then determined what was and wasn't needed from an audio perspective.
I've basically determined that there are three things that give the A203 it's distinct sound:
- harmonic content of waveforms (primarily a by-product of the 4-bit digitization of volume)
- the random number generator used in the noise channel
- sweep algorithm and timing
These are the portions of the 2A03 that are replicated exactly in the 2A03 Synthesizer.
- waveform shape / harmonic content
- waveform volume quantization
- frequency sweep algorithm and timing
- decay generation and timing
- noise random number generator
Now, to "expand" the synthesizer I've added the following features. I've detailed how these features differ from a real 2A03.
I've considered possibly adding the following features in the future:
- support for audio panning
- addition of LFOs and what not to modulate the waveform generators
- addition of filters, chorus effect, etc...
Feel free to drop me a line if you have any questions or comments about the synth.