Home 500-Series Page 1 of 1. Sort By: OLA5 Opto Compressor From $300.00 EQP5 Passive Equalizer From $200.00 PR502 2-Slot 500-Series Chassis Kit From $150.00 Colour 500-Series Palette mkII. Keep up on the world of DIY without leaving your inbox. The LA502 is a soft knee, electro-optical compressor based on the LA2A/LA3A design, which we have adapted to the '500' series format. MC624 The MC624 is similar to the monitor section of a mixing desk: it lets you select one out of six stereo audio sources, adjust the level and route it to one of four monitor outputs.