Store demo unit with minor cosmetic marks.

The Warm Audio WA-2MPX is a dual-channel tube microphone preamplifier that reproduces the AMPEX 351-style preamps found in the American tape machines that defined the sound of early rock and roll, radio, and studio recording. Each channel delivers up to 90 dB of tube gain through a 300V circuit with three vacuum tubes and custom CineMag USA transformers, providing a wide tonal range from pristine clarity to rich tube saturation.

Tube Circuit and Gain Staging

Each channel runs two 12AX7 tubes and one 12AU7 through a 300V signal path. The first 12AX7 operates as the preamplifier stage, delivering 70 dB of clean gain in standard mode. Engaging the High Gain switch brings the second triode of the first 12AX7 into the circuit, boosting available gain to 90 dB for low-output dynamic and ribbon microphones. The 12AU7 drives the push-pull output stage through a CineMag USA output transformer. The Tone switch toggles input transformer impedance between 600 and 150 Ohms for additional tonal variation.

Tape Saturation

Each channel includes a selectable Tape Saturation switch that engages a discrete analog circuit providing compression, harmonic distortion, and non-linear frequency response to emulate the sound of tape machines running at 15 IPS. Combined with the 80 Hz high-pass and 2 kHz low-pass filters, the WA-2MPX can shape tone from full-bandwidth clarity to focused, lo-fi warmth.

Specifications

• Type: 2-channel tube mic/line/instrument preamplifier
• Topology: AMPEX 351-style, fully discrete, hand-wired
• Tubes per channel: 2x 12AX7, 1x 12AU7
• Transformers: CineMag USA (custom large-core, input and output)
• Gain: 90 dB per channel (with High Gain engaged)
• Circuit voltage: 300V
• Filters: 80 Hz high-pass, 2 kHz low-pass (per channel)
• Tape saturation: Selectable, emulates 15 IPS reel-to-reel
• Controls per channel: Input gain, output level, input select, 48V, polarity, tone, high gain, HPF, LPF, tape saturation
• Inputs per channel: XLR mic, TRS line, TS instrument
• Outputs per channel: XLR, TRS
• Metering: VU meter per channel
• Power: 115/230V, IEC
• Rack size: 2U, 19"
• Dimensions: 483 x 222 x 89 mm (19 x 8.7 x 3.5")
• Weight: 3.7 kg (8.2 lbs)

In the Box

• Warm Audio WA-2MPX
• IEC power cable