This is an upgrade over the original DigiMAX, featuring less-expensive chips, channel auto-switching (including lockout to allow for manual/deliberate switching), and a more modern design in general.

This design combines the basic features of the original DigiMAX Mk1 with the 8BSS project, all in one small package, providing two 8-bit DACs and two 8-bit ADC's on the User Port, with a new auto-switching function which makes writing or reading sample data as fast as if the chips were on the Expansion Port, if the user's program is aware of the new functions. By default, it operates in manual switching mode.

For writing/music playback, it is backward-compatible with the original DigiMAX Mk1 (when using the first two channels thereof -- but probably no one used all four channels, because they were too slow, so this design only has two channels), and also with software that only uses a single DAC or R2R ladder.

Sadly it was not possible to retain full compatibility with the old 8BSS, but in reading/ADC mode, it will at least capture in 8-bit mono if the program is not aware of the new design. Stereo capture requires a new protocol (but it's still simple).

Designed for use with all Commodore 64 and 128 variants.

If you omit the female edge connector and install a 2x13 (26 pin) female IDC connector on the "back" (same side as the edge connector would go), with the key/latch oriented away from the chips, this design can also plug directly into the internal User Port header on C64 Ultimate or Ultimate64 boards, without the need for the extension/adapter board.

Some of the parts are (surprisingly) made only in the US, so if you're located there and want to build this project, you may be best-served by having PCBWay make the PCBs, unpopulated, and then sourcing the parts from, say, LCSC or DigiKey. All items in the BOM are specified using both Digikey and LCSC part numbers.

The Mk2 has been prototyped, and all functions have been tested and seem to work, at least in the first prototype. That prototype is full of bodges 🙂, and I've revised the audio output circuit, so a new board revision to account for them is in progress.

THIS PROJECT IS STILL EXPERIMENTAL.