I finally got around to building the rare version of the Fuzzrite from a Mosrite amp. There's more detail here:
Here's the original:
I cleaned it up and simplified it for an easy build:
First note...the schematic shows 35v supply thru 47K resistor. 9v works fine without the resistor.
I built it with silicon transistors in the 100-150 hfe range and it was excellent right off...but I've always liked the germanium versions of Fuzzrites & variants better, so I decided to go with that.
Like the Orpheum, it's sounds killer with a a Q1 in the 80-120 hfe range and a Q2 in the 50-70 hfe range. The big difference here compared to a normal Fuzzrite is that it's fatter, most likely due to the larger output caps (.0047uF/.01uF instead of .002uF/.002uF), which is closer to the germanium Orpheum (.005uF/.005uF).
The silicon versions are harsher and can get really trashy with fuzz at full. The germanium versions can get much buzzier. To give the option of having the germanium version harsher, I added a simple mod, which works like a perfect tone control here. I used a 200K pot in place of the 100K R so the stock tone is centered....full counterclockwise is bassy-er and full clockwise you get some beautiful trebley harshness....but with germanium, never too harsh.
I ran into one odd problem here that I never have before with a Fuzzrite variant. There was wild oscillation with fuzz at the lowest setting. A simple 2K cutoff solved that problem.
Here's my final version of this killer:
btw, if anyone knows the model of the amp this came from, please let me know. I can't finish this box without etching the correct model number into the bottom of the box...