The x0xb0x blueprints are the work of a couple of MIT students (now graduates) who set out to recreate the TB-303 as closely as possible.

An original TB-303 was disassembled and reverse-engineered to verify the schematic. The original transistors were analysed using big expensive curve-tracers to determine their characteristics. We measured every waveform and counted every cycle. — x0xb0x creators

The x0xb0x copies not only all of the electrical interconnections inside a TB-303, but incorporates the old, rare analog components, such as 2SC2291 matched-pair transistors and AN6562 op-amps. Consequently, it has earned the reputation of having the most faithful sound of all 303 clones. The difference in sound between a well-made x0xb0x and a TB-303 is about the same as the difference between one TB-303 and another.