API 550A Discrete 3 Band EQ

The API 550A provides reciprocal equalization at 21 points in 5 steps of boost to a maximum of 12dB of gain at each point. The fifteen equalization points are divided into three overlapping ranges. The high- and low-frequency ranges are individually selectable as either peaking or shelving, and a band-pass filter may be inserted independently of all other selected equalization settings. Frequency ranges and boost/cut are selected by three dual-concentric switches, and a pushbutton "in" switch allows the EQ to be silently introduced to the signal path. A small toggle switch is used to insert the band-pass filter into the 550A.

Specifications:

• 3 bands of classic API equalization
• Each band offers 7 API-selected frequency centers
• Reciprocal and repeatable filtering
• Maximum 12dB 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 +30dB clip level