Great-sounding vintage units.

-Serial numbers on the units are from the late 70s and are only 50 numbers apart: 4305 and 4355. 2520s are all from Melville, NY, which were manufactured from 1972 to 1975. At some point, one of the 2520s was replaced with the Avedis 1122 Op-Amp. See Pics.

-We would love to sell the 2 Modules and Rack together. They sound great as a stereo pair.

The API 550A vintage equalizer is a highly celebrated 3-band modular EQ originally designed by Saul Walker in the late 1960s. It is built on fully discrete circuitry featuring Walker’s iconic 2520 op-amps, delivering high headroom, exceptional clarity, and a punchy analog character.

From a smoke-free studio that takes excellent care of its equipment.

• 1st Unit has the two original Op-Amps
• 2nd Unit has one original Op-Amp and one Avedis Op-Amp
• 3 bands of classic API equalization
• Each band offers 7 API selected frequency centers
• 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

Fredenstein Bento 2 500-Series Rack Features

• Universal power supply accepts mains voltages ranging from 90V AC to 240V AC, 50 to 60 Hz.
• Increased output currents are as +/-16V DC 0.9A and +48V DC 0.033A
• Additional TRS inputs and outputs parallel to the XLR connectors.
• Built-in Audio Routing (Slot 1 can be daisy-chained to Slot 2 by simply flipping a switch on the back panel)
• Compressor buss linking (Compressor modules can be linked by engaging a switch on the back panel as well)
• Secondary power switch and voltage indicators are on the front panel