Siemens U273 Compressor (Vintage)

The first limiter ever made was the U3 by Telefunken of Germany, which debuted at the Olympics in Berlin in 1936. As radio broadcasting was becoming more prevalent, there was an increased demand for a device that could protect broadcast facilities, (and listeners at home), from the sudden changes in volume that arise from input overloads.

Over the next two decades, the design of this limiter was upgraded in the U13 and U23 models. Finally in 1956, the U73 model was developed, using many of the same components of the famed Telefunken U76 pre-amplifier. The U73 was licensed to TAB for production, and became the last of the tube compressors created by Telefunken.

Once the transistor appeared, engineers were replacing tubes in almost every device possible, and the limiter was no exception. Thus the Siemens corporation, as part of their "Sitral" series of modules, developed a version of the U73 as the world's first sold-state compressor, and named it the U273.

In some respects the Siemens unit is similar to the famous Neve 2254 compressor, but with transformer-balanced inputs and outputs featuring Haufe transformers, the Siemens U273 has its own characteristic sound - while nice and round at lower levels, it can be thick and gritty when pushed hard. Many engineers consider it one of the best sounding solid-state compressors ever made.