The Vacuvox CL2 compressor/limiter, which was succeeded by the Vacuvox U23, is a highly regarded tube compressor/limiter that draws heavily from the original Rohde & Schwarz U23 broadcast limiter design. Many original components from the U23 were reused in the CL2, including the chassis, which differs from the standard 19-inch rack format, contributing to its distinctive design.
The Rohde & Schwarz U23 was originally designed with a single, specialised purpose: to prevent overmodulation of broadcast transmitters. Its controls were minimal, offering no flexibility for broader studio applications.
In contrast, the Vacuvox CL2 was designed to meet the needs of recording and mixing engineers by incorporating additional control parameters. Key upgrades included adjustable attack and release times, as well as a variable compression ratio. The circuit was also modified to improve operational stability across a wider range of use cases, making it far more versatile than its broadcast-focused predecessor.
Interestingly, the designers of the CL2 did not prioritise achieving the lowest possible distortion levels. Instead, the unit intentionally introduces subtle second and third harmonic content when the gain is reduced, creating a rich, harmonically enhanced sound that listeners often describe as louder, warmer, and more euphoric. This characteristic harmonic saturation is one of the defining features of the CL2 and contributes to its unique sonic signature.
Users frequently express their amazement at the dramatic improvement in sound quality and functionality offered by the Vacuvox CL2 compared to the original Rohde & Schwarz U23. By balancing the vintage charm of the original design with modern usability enhancements, the Vacuvox CL2 became a standout tool for engineers seeking both character and control in their dynamic processing.