Yes I have done a few of his mods for people and most are an improvement. This one on the SD1 was far better than one of his earlier mods for them. I'm guessing it is the Ge transistor as a clipping diode. When it is selected the sound has a real bite to it, similar to the way the rangemaster treats the treble boost. well next project is a Fulltone style Fat Boost on a perf board....