The Vacuvox U23 vari-mu compressor/limiter builds upon the legacy of the renowned Vacuvox CL-2, which was originally based on the Rohde & Schwarz U23 broadcast limiter. With numerous enhancements to both design and functionality, the Vacuvox U23 retains the rich, euphonic sound of the original while introducing modern improvements.
The Vacuvox U23 features a fully Class-A vacuum tube audio path and side-chain, based on the Rohde & Schwarz U23’s original circuit. This ensures exceptional headroom, transparency, and performance.
The Vacuvox U23 is meticulously hand-assembled using premium modern components. Its custom-made transformers are faithful recreations of the sonically exceptional originals used in the Rohde & Schwarz units. The four audio transformers are crafted with a permalloy core, consisting of 80% nickel and 20% iron. The audio chokes and power supply components use high-grade SiFe (Silicon-Iron) cores. The power transformer has been upgraded to deliver enhanced noise performance and greater stability.
Key upgrades in the Vacuvox U23 include a reworked front panel layout, refined output gain and threshold controls, and two additional gain stages. These changes further improve the unit’s flexibility while maintaining its vintage tonal character.
Designed for both general tracking and mixing, the Vacuvox U23 uses precision potentiometers for controlling input, output, attack, and release parameters. For mastering applications, the Vacuvox U23m version includes 21-stepped switches for fine-tuned adjustments, making it ideal for critical stereo applications across a wide range of genres, from jazz to classical music. The mastering version ensures precise stereo balance without compromising dynamic integrity or introducing unwanted artefacts.
The compressor/limiter’s gain structure options – adjustable via the pad, input gain, and threshold – enable a variety of tonal possibilities, from transparent and clean to saturated and dense. By adjusting the threshold, input transformer, or tube drive, users can achieve a wide range of sonic textures.
