Urei LA3A Consecutive Pair Compressors (Vintage)

Racked pair of vintage Urei LA-3 Leveling Amplifier’s. Solid state version of the classic LA-2A T4 tube optical limiter. Fully discrete.  This stereo consecutive pair (#398 & 399) has been modded with a stereo link switch on the right hand unit (see photo).  Rich tone, big and full. Always on great on individual instruments. Now with the stereo link an exceptional bus compressor as well.

Introduced in 1969. The LA-3A is a solid-state version of the LA2A; it retains the same simple control set (Gain, Peak Reduction, Comp/Limit Switch) and, of course, the all-important T4 electro-optical panel module (ELOP for short)—the source of the great program-dependent compression characteristics of the LA-2A.

Sound-wise, the LA-3A is quite different from the LA-2A, even though it uses the same T4 ELOP as the LA-2A. For small transients, the attack will be about the same for the LA-2A and LA-3A; whereas for large transients, the LA-3A will be faster. This is because the LA-2A uses a tube to drive the ELOP panel directly, and the circuit has a certain maximum voltage level. The LA-3A, in contrast, uses solid state, which can’t generate enough voltage to drive the ELOP panel. So, there is an “autotransformer” in the circuit to boost the voltage going into the ELOP panel.

Thanks to this design, with the first part of the attack on a large transient, the ELOP panel will be brighter in the LA-3A, making the first part of the attack faster. For the last part of the attack (or for smaller transients), once the sidechain voltage has decreased, the attack time will be about the same as the LA-2A.