Chuck D. Bones
Circuit Wizard
I had been meaning to breadboard this one for some time now, finally got around to it during a break from compressors. I built it by the book, except I used fixed resistors (3.3K, 15K, 15K 15K) instead of trimpots and auditioned JFETs until I hit the recommended drain voltages. I tried a couple of mods: asymmetric clipping on stage 3 and increased gain on stage 2, but neither sounded as good as the original design. I am not a fan of the cab sim at the tail end, makes it sound too thin. This circuit would benefit from a PRESENCE control after Q5. It's a clever design, similar to some of the other ROG amp-in-a-box circuits. The LEDs up front are for protection only and don't normally conduct. The 1st & 2nd stages don't distort, in fact the diodes just after the TONE control don't get enough signal to turn on. Q3, Q4 and their diodes do all of the clipping. Q5 makes a 2nd-order low-pass at 6.7KHz that simulates the bandwidth of an output transformer.