Optical compressors may contain tubes and transformers, or they may be solid-state and even transformerless. The LA-3A, an opto compressor with the tone of an 1176. The emphasis control was designed to provide radio stations with better control over the broadcast signal’s high-frequency content. This screw exists on the original hardware units (sometimes on the rear panel) and was factory set and perhaps adjusted by a studio tech to suit the studio’s preferences. Most digital models of the LA-2A and LA-3A provide an emphasis control (sometimes labeled pre-emphasis) that often looks like a slotted screw. Remember that the frequency-dependent nature of the opto blurs these parameters a bit-in a musically helpful way. The LA-2A provides two modes: compress (3:1) and limit (100:1). The fixed attack is fast, while the fixed release happens in two stages as described above, and would be generally characterized as slow. The user-adjustable parameters of an opto compressor are output gain and gain reduction (threshold). The compressor then adds make-up gain with a tube amplifier (LA-2A) or a solid-state amplifier (LA-3A). In effect, the audio signal lights a small light panel and a nearby photoresistor senses the light and controls the behavior of the gain reduction. The magic of the LA-2A, and every other optical compressor that followed lies in an optical circuit that acts as the level control, or attenuator. Universal Audio manufacturers an extremely popular hardware reissue of the original LA-2A to this day. By the mid-1960s the LA-1 developed into the current LA-2A compressor design- which has become a staple both as recording hardware and DAW-based software. Optical compressors date back to the 1950s when Telektronix (which eventually became part of Universal Audio) debuted the LA-1 compressor. I seemed to like the CLA-2A when compressing lightly, but the UAD LA-2A when compressing heavily (the CLA-2A sounded too harsh at high peak reduction).The LA-2A hardware reissue from Universal Audio. Ultimately, individual taste and type of application should dictate the compressor of choice. In contrast, the CLA-2A may sound a bit more natural when used on simple drum loops because it tends to preserve the transients better in that particular application.
The UAD LA-2A also sounds a bit warmer (or alternatively darker) on some of the more complex sources such as a full mix or a snare & hihat mix. One explanation could be that the UAD version has both faster attack and slower release (or it could be simply different approaches to animating the compressor needle). This is a bit unexpected given that the needle on the CLA-2A moves much faster than the needle on the UAD LA-2A. The UAD LA-2A has a bit faster attack which tends to compress transients more. Interestingly, the two LA-2A emulations differ quite a bit on some of the sources. The CLA-2A seems to have a slower attack which tends to preserve transients more so than the UAD LA-2A. Both plugins have their own unique sound. Judging and comparing the sound of the two products at such a subtle level of compression can be quite challenging. The shootout consists of two parts – the first part compares the plugins when compressing very slightly (about 2dB) and the second compares the sound when compressing heavily (about 8dB).īelow are my conclusions but go ahead and have a listen for yourself. I have created another comprehensive shootout comparing the sound of the UAD LA-2A and the CLA-2A.