Boss PQ-4 Parametric Equalizer
The PQ-4 is a three band equalizer that allowed for "spontaneous sound creation". The complex interface of the PQ-4 was overwhelming for some, so the effect wasn't the biggest seller at the time of it's release. Nowadays it's a very desirable pedal due to it's short production and huge range of tone shaping possibilities.
The Presence knob controls the extreme high frequencies, the Low knob controls the level of the lower frequencies, the Middle and High Level knobs boost or cut their respective frequencies and the Level knob controls the output volume level (from -18dB to +18dB). The Middle and High knobs also feature individual Frequency knobs to shift the centre frequencies (100hZ to 1.6kHz for Middle and 500hZ to 8kHz for High).
Produced from March 1991 until December 1995.
The PQ-4 is the only Boss compact pedal to use the "-4" suffix, as the number 4 is considered unlucky in Japan.