Both NEW ("feed forward") and OLD ("feed back") methods are selectable on the front panel, providing two choices of gain reduction. NEW gain reduction is typical of the newer VCA type compressors that rely on RMS detectors for the gain control voltage. OLD or Feed-Back method is what most of the classic compressors used for the gain control circuit There also is a SOFT or HARD selector. SOFT provides a more subtle compression resulting in a very natural, less compressed sound. HARD results in a more typical, sharp knee type compression that has a much more severe limiting effect.

Release time is adjusted by rotating the inner concentric R knob. Release time constants: continuously variable from .3 seconds to 3 seconds. Attack time is adjusted by rotating the outer concentric A knob. Attack time constants: continuously variable from 1 millisecond to 25 milliseconds.

API's 225L is designed for individual channel use, or through the use of the external LINK funcauto-makeuption. Two units can be combined for Stereo applications via a rear access pin. The 225L also has a side-chain input for the detector amplifier.

The 225L can be used in the Legacy, Legacy Plus or Vision Series Consoles, or in the L200 Rack. The 225L Compressor makes use of the 2520 and 2510 op-amps and therefore exhibits the reliability, long life and uniformity which are characteristic of all API products.