A Glimpse into History
 
Roland Corporation, founded in the early 1970s, was already making waves in keyboards and amplifiers when it entered the stompbox world. In 1975, Roland introduced a small line of effects pedals under its own name—among them the AP-2 Phase II.
These early Roland pedals coexisted just before the now-famous BOSS brand fully took over Roland’s foot-pedal identity. In fact, by 1976 and later, many effects were marketed under the BOSS name, but the AP-2 remains a direct link to Roland’s original forays into guitar effects. (tonehome.de)
 
The pedal’s specifications and design
It offers two basic controls: Rate (speed of the sweep) and Resonance (which shapes the feedback and how sharply the effect peaks).
Powering it is an interesting detail—rather than the common 9V single battery, the original design used two 9V batteries in series to create an 18V supply with no external DC input.
 
Legacy and rarity
Due to its limited production run and its place in a transitional era for Roland / BOSS, the AP-2 is now a coveted vintage piece.)
Even today, fans of vintage tone admire the pedal for its smoothness, warm modulation, and the subtle resonance it can impart—tones that many newer phasers strive to replicate but rarely fully match.