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.