Warm Audio WA-MPX B-Stock

The US manufacturer Warm Audio has earned a first-class reputation as a specialist in the successful reinterpretation of classic recording technology. The key elements of the original circuits are carefully replicated in each case on the basis of the respective prototypes and expanded to include useful extras, and the prices are surprisingly affordable as well. The Warm Audio WA-MPX sees the Texas-based company stepping back into the golden era of Rock & Roll. This single-channel microphone and instrument preamp is inspired by a legendary tape machine preamplifier from the 1950s and is Warm Audio’s first tube-driven device. Unlike the bulky prototype, the WA-MPX comes in a compact 2U format and is equipped with everything that modern studio environments require.

The Warm Audio WM-MPX is a hand-built and fully discrete preamp, which features three tubes and CineMag transformers in the signal path. In addition to a full 90dB of tube power, the device also boasts a switchable tape saturation control and a filter circuit to emulate the sound of tape machines running at a speed of 15IPS. This allows the WA-MPX to deliver an authentic and powerful sound with an exceptionally pleasing tone and natural-sounding compression. A 2kHz low-pass filter, 80Hz high-pass filter, and impedance switching permit extremely flexible sound configuration. XLR and jack sockets are located on both the input and output side, and the front of the device is equipped with an additional instrument input. Phantom power, a polarity switch, and a stylish VU meter round off the range of high-level features.

The use of high-quality and to a large extent authentic vintage technology allows the Warm Audio WA-MPX to deliver distinctly characterful sounds. The MPX is the go-to wherever sufficient punch with a warm tone, or even extensive saturation, is required during the recording process. The powerful and, where required, even biting mid-range sound produced by the MPX makes it particularly suitable for signals typical in Rock music, such as basses and electric guitars, but also the perfect device for drums, overheads, or even vocals. Warm Audio’s customary professional quality is on display in terms of both build quality and features here, and project and semi-professional studios alike wishing to add a veritable sound tool to their range of “all-rounder preamps” may also find the WA-MPX attractive thanks to its comparatively low price.

As users have come to expect from Warm Audio, the manufacturer has expanded the essence of the original circuitry here to include a number of useful extra features. The WA-MPX accordingly uses two 12AX7 tubes (like the original) for the first amplifier stage and a further double triode (12AU7) for an additional 20dB boost, which is activated with the MPX and controlled by the gain control. The transformers are custom-made by the legendary US transformer manufacturer CineMag, once again to vintage specifications. By contrast, filtering, tape saturation, and impedance switching are found exclusively in the Warm Audio interpretation and considerably enhance the tonal flexibility of this preamp.