JOYO Technology are co-founders of Dr J guitar effect pedals. Dee Leung, head of the Dr.J engineering team in Shenzhen, began his career as a musician. He liked fiddling with various pedals when he was a student in college, analyzing tones and circuits from low-end pedals to advanced handmade ones. Dee Leung continued focusing on his pedal designs in his evenings, at home as his passion for electronics grew into an obsession. Although he had bought some pedals, he couldn’t afford to collect so many of the costlier effects, so he made an effort to network with local guitarists and other effects-using musicians with sizeable pedal collections of their own. 

Dee took his overdrive pedal prototype to those musicians who had lent him pedals over the years for them to try out and to thank all his friends for their years of support, Leung gave his new pedal to each one as a gift. The overdrive pedal gained increasing popularity, and more and more local blues guitar players asked Leung for a custom-made unit, which was the predecessor of the Dr J. Green Crystal.

Terry Li from JOYO, one of the founders of Dr.J, was among the earliest users of the Green Crystal. Terry was preparing a start-up to market select pedals with the aim of bringing musicians a new kind of inspiration. This idea caught the attention of JOYO Technology which later assisted with investment for the DR.J effect pedals brand start-up. That moment was the turning point that allowed the independent development of this new brand--what is now Dr.J--to become possible. Terry Li named his pedal company after the first initial of his favorite guitar player, Jimi Hendrix.

Source: Joyo website (Archived 2014)