This particular MIDIbox by [Subatomic] is built on the MIDIbox SID specs originally conceived by [Thorsten Klose] (check out the great sound samples) and streamlined by [Wilba]. It uses a Commodore 64 case, 8 of its SID chips, and the power supply, but gets most of its other parts from various different sources. The Commodore’s SID or Sound Interface Device, was one of the first sound chips available in a personal computer.
In the worklog, a SID module, the first of four, was built before anything else. Then [Subatomic] opened up the Commodore case and attempted to fit a number of modules into it. For the MIDIbox’s power, he converted the original Commodore power supply to provide 14VDC and 5VDC, but learned much later that this would only give enough power for 4 SIDs, resulting in a mono MIDIbox. He continued by adding a power board and noting that with the core and SID modules and the audio mixer board, it’s a tight but workable fit.
The next several steps involved designing and building the control surface. After creating a mockup and acquiring several components like knobs, LEDs, and a small LCD, [Subatomic] began building many of the necessary control surface PCBs, including the filter control PCB and a few others.
[Subatomic] went on by going through the painstaking process of creating backlights for the knobs. After that he acquired the custom-made front panel, created the LCD module, and attached it and several PCBs to the panel. The panel was then painted.
After a little work on the PSU and the rear I/O panel, [Subatomic] prepped some banksticks (external storage accessories; think USB stick forerunners with a female serial jack).
After finishing and gluing the LEDs to the knobs, the panel was finished. At this point Subatomic decided to scrap the SID, core, din and dout modules in favor of a single PCB that does everything. He cut the board to make it fit in the case, cut headers, added resistors, burned out the LCD, did a lot of spot-checking on the wiring, and then he finally added the SIDs to the board.
He soon zeroed in on the power supply problem that was only routing enough power to 4 SIDs by replacing the malfunctioning C64 PSU with a good one, after which the LCD was also replaced. The wiring diagram above shows how the remaining modules would be wired to the main board.
The only software work involved adding functions for 2 special buttons to the preexisting firmware and recompiling it. He realized that the MIDIbox was missing a mixed output jack, so he added than and made several minor cosmetic mods. With these final fixes, the MIDIbox SID was completed. If you’re considering this project, be aware that it’s a major endeavor with a lot of detail work that took [Subatomic] nearly 3 years to build, but the reward is a slick-looking, fully functional MIDIbox SID of your own.