This Week on the Breadboard: the Cinnabar

Chuck D. Bones

Circuit Wizard
This is a strange little circuit that easily meets the Express Lane criteria. There are only seven parts + pots, switch, jacks & battery.

I used 2N5089 for Q1, 2N5210 for Q2 and 2N5457 for Q3. I ended up lowering the 100K to 47K for a little more gain & output and increased the 1nF to 2.2nF to smooth out the top end a bit. The TIMBRE pot is B2M; the CW end is towards the cap. The input impedance is low when GAIN is cranked, so this pedal is best placed first in the chain. As the note on the schematic says, this circuit goes from smooth to spunky. There's a fair amount of sustain and for all but the most extreme settings the note decay is smooth. It's a little splatty when GAIN and TIMBRE are cranked, but not nearly as much as a Tone Bender or FZ-1. It has a strong bottom-end. A fun little pedal that will end up on a Vero board.

When I first saw this schematic, I thought "how the Hell can that even work?" But work it does. Q2 is run in "reverse beta" mode, much like some of the DBA pedals. Q1 is biased right on the edge of saturation. I could never have designed a circuit like this, it's just too weird. Sometimes too much electronics knowledge is a hindrance.

Just about any JFET will work. Since the operating current is in the 10 to 20uA range, even the coldest JFETs (low Vp and Idss) will work. If you don't have a 2M pot, try 1M. If you run this from a power supply, then a 100uF filter cap would be a good idea.