The original mobile audio amp designed by BK Butler was marketed by his own
company. Phaze Audio bought the rights to the Tube Driver name/design and
marketed the 2nd version of the amp. After Phaze Audio bought Precision Power,
the 3rd version was designed by and marketed under the PPI brand name
[supposedly, PPI hired a couple of engineers away from Krell to design the
amp]. Then the relationship between Phaze Audio and PPI soured and PPI was sold
to ADST, the parent company of a/d/s. When a/d/s, Orion and PPI were bought by
Directed Electronics [DEI], BK Butler bought back the rights to the Tube Driver
name and BK redesigned the amp, giving us the 4th version.