This unit is in excellent condition and has been used in home studio only. The API 550A is a three-band switchable EQ module for 500-Series format.

Since the late '60s, the API 550A has been a staple of the American recording industry - included in both API and custom-made consoles. The original 550A modules have become so sought-after that they were the logical inclusion for the open-access 500-Series format that API invented.

A simple switchable three-band EQ, the API 550A has selectable shelving on the high and low bands with an independent band-pass filter. Proportional Q on the 550A allows smooth transition between the three frequency bands, gradually narrowing as more EQ is applied, up to 12dB.

The sound is unmistakably API - full of character and presence, with plenty of headroom and all the tonal sweetness that you need, to bring out the best in your instruments. Putting the API 550A into a Lunchbox, 500 Series gives you the power to use that fabled quality on the move.

API 550A Overview:

• 3 bands of classic API equalization
• Each band offers 7 API selected frequency centres
• Reciprocal and repeatable filtering
• Maximum 12 dB of boost/cut per band
• EQ Band 1 and 3 offer shelf/peak switching
• "Proportional Q" narrows filter Q at extremes
• Traditional API fully discrete circuit design
• High headroom +30 dB clip level