Moving on with the Odyssey mods..
I wanted to add CV/Gate I/O to the Odyssey without drilling the enclosure (reversible modding FTW). No choice but to make the mods external, maybe route some other signals as well.. As you probably guessed already, here’s where my Breakout Box comes into play!
Looking around the net I found some old posts where Gene Stopp had provided his solution, so I took that as a starting point. For the interconnect between the box and Odyssey, I cut up a old 25-pin DSUB extension cable. No need to solder connectors and the cable fit neatly through one of the jack holes on the rear. Who needs a sustain pedal anyway ;).. Here’s the schematic for the Breakout Box:
For the casing I picked this old plastic project box I had lying around. It somewhat matched the main colors of a whiteface Odyssey so in that sense it was a rather obvious choice.
Ok, so this here is a circuit that can be used to lower the background noise generated by a SID chip quite dramatically. It works for both SID models. The basic idea is to separate the SID from the data/address buses of the C64 when the chip is not accessed. As the digital and analog sides use the same ground, the more rapidly changing digital signal bleeds to the analog side through the common ground (hence the background noise).
(Click the image to download the pdf)
I wanted to draw a board of my own even though Raphaël has everything needed to etch a board. My design was supposed to have both PLCC and DIP sockets on the same board but I didn’t manage to fit them within a reasonable sized PCB. :/
As some demoparties (like Breakpoint) require you to demonstrate that your compo entry runs on real hardware, having this cart would’ve allowed me to enter music made on/for Megadrive to such parties.
(Click the picture to download the pdf, etching mask is here)
Board is not tested, so if you decide to try this please let me know how it turned out!
Parallel to building my TB 3k3 I had been, to some extent, getting acquainted with various sequencer designs. After taking my time searching and evaluating these, I ended up with a slightly modified Superseque schematic. This design, by Thomas Henry, is about as simple as it gets whilst still having a formidable set of features like sequence playing direction. I modified the schematic to include a second 555 timer chip as the original design relied on external sync alone. The sync source is simply selected with a switch. I also opted to use SMD parts where ever possible as this simplifies the board manufacturing procedure a lot, I get my share of drilling through-holes with the Vocoder project anyway..