The API 2500+ Stereo Bus Compressor allows adjustment of sonic qualities to alter the punch and tone of the stereo mix. The 19-inch, rack-mountable unit features a dual-channel design that can be configured for stereo compression or for use as two separate units via a single compression setting. Among the many qualities which make the 2500+'s unique is its use of API's patented THRUST circuit for a chest-hitting, punchy bottom end. Another distinctive feature of the 2500+ is its selectable "old" or "new" compression, with the old style using the "feed back" type of compression found in the API 525, and the new style using the "feed forward" type in which the compressor side chain is fed directly from the unit input. Additionally, the output stage of the 2500+ offers an auto-makeup gain button that permits the user to vary the threshold or ratio while automatically maintaining a constant output level.  Added to the 2500+ is the Mix/Blend circuit. First featured in the limited production 50th Anniversary Edition, Mix/Blend control provides either cross fader or parallel mixing of the compressed and uncompressed signal. Three different user settings are offered:  • OFF - compressed signal only • X (Cross) - allows the MIX control to adjust between 100% uncompressed to 100% compressed – increasing one, while decreasing the other • | | (Parallel) - allows the MIX control to dial in compressed signal to blend into the uncompressed signal, (which remains the same). The 2500+ en