Could learn a lot from that main board pic. I dont see any matched transistor pairs, everything looks like generic stuff. What I do see is the switching power supply and step up transformer identical to the 303s though and I have no doubt that that plays a HUGE role the the classic sound. After working on several different 303s and building 2 dozen x0xb0xes, that's really what I think is the root cause of the differences. What convinced me was to program a simple pattern that could be duplicated exactly on the 303 and x0x, there was a noticeable difference with the x0xb0x being more "stiff". What I did then was to drive the x0x CV/Gate ins with the CV gate outs from the 303 and you know what? I couldnt tell them apart. Conclusion: All this high beta/original part nonsense everyone goes on about is a drop in the pond compared to the influence of the power supply. With that part cloned correctly, it will make very little difference what transistors are used. Thats why the 303 used 3 different types (i.e. cheapo generic ones of the period). It's no doubt that is the reason all the new BCbox x0xIO devices had a redesigned PSU to match the orginal instead of the AC powered voltage doubler in the x0x
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