The Synapse AP-12 rack extension emulates vintage analog phasers, which are composed of a series of phase shifting stages with a feedback path wrapped around them. The phase shifting stages (switchable between 6 and 12 stages) are modulated by a LFO, which can be synchronized to the current song tempo. In contrast to most hardware phasers, the AP-12 employs a stereo signal path, allowing the LFO to use different phases on the left and right channel, and thus creating a nice stereo effect. Furthermore, the feedback can be set to both positive and negative amounts, each resulting a in different timbre.