Vox Phaser (top right) in the studio, 2009

Fat, grey V-shaped phase pedal, with knobs for depth and speed of phasing.
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Featured in a video of Billy's huge collection of guitar pedals called Stompland - it was still in the box. It was also seen in a group of effects in a video of Billy playing A Song For A Son on Kerry's blog on 2009/10/12, but did not appear to be plugged in- he may have been experimenting with various effect pedals, as the Maestro PS-1 was in use in the video, and several other effects are visible.