The Refractor project is a straight-up clone of the Klon Centaur and Klon KTR. My goal in designing this PCB was space efficiency: there’s no shortage of Centaur clones that fit in larger enclosures, but mine was made for the 1590B (1290NS)—though it’s just as much at home in a 125B if that’s your style.
One perennially tricky thing about building a Centaur clone is wiring the bypass switch. Due to its unique buffered bypass arrangement, for most clones you have to solder three resistors to the switch itself and it can be time-consuming. To compensate for this, I’ve designed a bypass board that fits standard 3PDT switches and has spaces for all three resistors. From there, all you need to do is run four wires from the bypass PCB directly to the main PCB and you’re done. It’s available separately as the Refractor Bypass.