To fully appreciate the value of the Waves CLA Classic Compressors, it''s helpful to examine the original hardware pieces that these plug-ins were modeled on. What made them so unique and valued?
CLA-2A emulates the tube-based LA-2A opto-compressor. The LA-2A owes its lauded compression curve—famous for its preeminent transparency—to the T4 electro-optical cell it employs. The T4 comprises an electro-luminescent panel and photoelectric cell that has an inherently slow attack time (around 10 ms) and two-stage program-dependent release. The first stage of release lasts about 40 ms to 80 ms. The second stage can last several seconds when compression is heavy or the signal remains over the threshold for a long time. The two-stage release allows engineers to compress tracks very heavily with little or no modulation artifacts such as pumping or thinning.
CLA-3A is modeled on the UREI LA-3A audio leveler, an opto-compressor originally produced in 1969, which was basically a solid-state version of the LA-2A. Some other differences existed between the two processors, but most importantly they both used the venerable T4 opto cell and therefore had virtually identical compression curves. Compared to the LA-2A, the LA-3A has a more extended frequency response (both in the bass and high frequencies) and typically produces more depth. But the LA-2A''s creamy, somewhat band-limited sound still remains extremely popular.
The CLA-76 is modeled on the ''60s-era 1176 FET compressor. Whereas opto-compressors typically offer the slowest minimum attack time, FET compressors (those that use Field Effect Transistors for their gain-control elements) produce the fastest—as quick as 20 ms in the 1176. The 1176 is renowned for its ability to smoothly process instruments having sharp transients, such as drums.
The 1176 was revised more than a dozen times before production was discontinued. Waves CLA-76''s Bluey and Blacky modes model the Revision B (aka, Silverface Bluestripe) and Revision D-LN (aka, Blackface) versions of the 1176, respectively. The two versions of the 1176 have slightly different THD and noise specs, gain stages and time constants.