Old Rocktek Overdrive

[nio]

Does anyone know why the old rocktek overdrive sounds different than the newer one.  The old version was my first distortion pedal, and was sold a long time ago.  When MF had the overdrive for real cheap, I bought one for a little bit of nostalgia, only this version was actually a good ordinary overdrive.  I want my feedback at low volume, I want a volume knob that doesn't actually make it louder.  I was thinking maybe it has silicon diodes that can be switched out for germanium, but I wonder if anyone has any better ideas/explanations or the schematics to both versions.