The Charon Overdrive is a clone of the Ibanez CR5 Crunchy Rhythm, an overlooked gem in the Ibanez pantheon of the 1980s and early ‘90s. Released in 1989 as part of the original Soundtank series, the CR5 was produced up until the second series launched in 1992.
The drive section of the CR5 is very similar to the earlier DS-10 Distortion Charger from 1986. It uses a differential transistor pair in place of an op-amp for the initial gain stage. This is is sort of a low-tech op-amp in the sense that the gain can be adjusted with a potentiometer in the feedback loop. While Boss uses differentials in a handful of circuits such as the BD-2 and OD-3, these are the only two Ibanez circuits with a differential pair in place of an op-amp.
Following the differential stage, signal is hard-clipped via diodes to ground. This is where the similarities with the DS-10 end. From here, it passes into an op-amp stage that boosts bass at around 108 Hz to add back some low-end. After this, there’s a basic hi-cut tone control, volume control, and output buffer.
The Charon is a part-for-part recreation of the CR5 circuit with no modifications, except that the pinout of the transistors has been changed to the USA E-B-C convention (2N3904, 2N5088).