The xOxbOx (spoken socksbox) is an original concept from MIT students, who set their goal to product a real 303 clone, wich had to be 100% like the original. They took
a 303 apart and and by using "reverse engineering" and passion they managed to recreate a true clone, also by using much of the original circuitry and original
parts.
For those parts, which are not available any more, they technically found a way around this problem by using alternative parts and design but the same features. Weeks
and weeks were used to source the original parts worldwide and good alternatives were sourced. The xOxbOx does not copy all electronic circuits of the 303, furthermore
it also uses all critical and necessary components of the original Bassline, such as matched pairs of the 2SC2281, the LA4140 op amp and 2SC536F transistors.

The difference of a well made xOxbOx and a Roland TB-303 is probably the same difference as from a TB-303 to another TB-303 J