It was bound to happen sooner or later. Leave it to the innovators at Warm Audio to design a microphone preamp using classic tube electronics from the legendary American professional tape machines that recorded countless broadcast-ready hits during the golden age of analog. From rock pioneers of the ’50s and ’60s to today’s audio masters, the legendary “351” was the secret sauce in the signal chain that delivered the warmth and vintage color we all crave for our own recordings.

The Warm Audio WA-MPX 1-channel mic/line/instrument tube preamp combines authentic circuit design with premium build quality, faithfully recreating the sought-after analog sound of the original. Handwired and hand-assembled with premium components, including large-core CineMag USA transformers wound to vintage specs, the WA-MPX instantly delivers that “sounds-like-a-record” weight to tracks leaping out of the speakers. But there’s much more to this remarkable preamp that makes it essential for the modern hybrid studio workflow.

Original Circuit Design, Fully Featured

While staying true to the original circuit design, Warm Audio has added modern enhancements that make the WA-MPX impressively versatile in the studio. With the combination of preamp gain and output level controls, the Tape Saturation switch makes it easy to sculpt your gain structure from open and pristine to gritty and driven.

The classic Warm Audio Tone switch lets you adjust the impedance of the mic input transformer to optimize microphones or add extra analog color. There’s also a stellar-sounding instrument DI input, useful highpass and lowpass filters, phase reverse, and of course, 48V phantom power.

The WA-MPX runs on three premium vacuum tubes: two 12AX7s and one 12AU7. In a brilliant engineering move, Warm Audio included a high-gain switch that activates the third tube, boosting available gain from 70dB to a massive 90dB. Now you can confidently use your favorite low-output passive ribbon microphones on quiet sources with no worry!

Easy to Use, Built with Confidence

The WA-MPX brings vintage-inspired charm to the control room, with a design that pays homage to its tape machine roots. A brushed aluminum faceplate presents a logical, professional control layout, with large knobs and a warmly lit VU meter.

On the left, a rotary input selector switch allows you to choose mic, line, or instrument input. On the right, you’ll find the instrument jack and seven switches activating the features described above. Finally, the gorgeous VU meter is flanked by the preamp gain and output level knobs.

In use, the pots and switches feel smooth and confidence-inspiring. The WA-MPX is a very professional package — exactly what we’ve come to expect from Warm Audio. And for professionals needing more channels, note that Warm Audio also offers the WA-2MPX, a dual-channel version.

Unbelievable Value You Shouldn’t Miss

Warm Audio continues to impress audio professionals, and with the WA-MPX they’ve done it again — delivering a hand-assembled, feature-rich boutique tube preamp at an incredible price.

Its flexible gain structure lets you drive the tubes and dial in natural harmonic distortion and compression for a true reel-to-reel 15 IPS vibe. The WA-MPX provides mic/line inputs and balanced XLR and TRS outputs for easy integration into your studio or portable rig.

With rugged metal construction, durable rackmount faceplate, and fully discrete handwired internals, it’s the ideal preamp for front-of-house, studio, or remote recording. It includes a robust internal power supply with selectable 115/230V operation, ready for worldwide use.

Considering its surprisingly affordable price, the WA-MPX represents outstanding value. Enhance your recordings with legendary tone: the Warm Audio WA-MPX tube preamp.

Features:

• Faithful recreation of the legendary “351” tube tape machine preamp
• Fully discrete, handwired, handbuilt design with up to 90dB of clean analog tube gain
• Selectable Tape Saturation switch adds harmonic distortion and natural compression for authentic analog “grit”
• Large-core CineMag USA transformers wound to vintage specs
• Tone switch adjusts mic input transformer impedance for mic optimization or added analog color
• 600Ω output pad
• Vacuum tubes: 2 x premium 12AX7, 1 x 12AU7
• Preamp Gain: 70dB, up to 90dB with High Gain engaged
• High Gain switch activates third tube, adding 20dB of clean gain for low-output mics and quiet sources
• 48V phantom power; phase reverse switch
• 80Hz highpass filter tames unwanted low frequencies
• 2kHz lowpass filter emphasizes midrange warmth and punch
• Inputs: XLR Mic, TRS Line, TS Instrument
• Outputs: Balanced XLR and TRS line-level
• Warmly lit VU level meter
• Frequency response: 20Hz–20kHz
• Each unit hand-inspected and tested at Warm Audio HQ in Austin, Texas
• Also available as a dual-channel version: WA-2MPX

Specifications

• Preamp Type: Tube
• Number of Channels: 1
• Phantom Power: Yes
• Phase Reverse: Yes
• EQ: 80Hz highpass filter, 2kHz lowpass filter
• Tubes: 2 x 12AX7, 1 x 12AU7
• Analog Inputs: 1 x XLR, 1 x 1/4″ TRS, 1 x 1/4″ Hi-Z (front)
• Analog Outputs: 1 x XLR, 1 x 1/4″ TRS
• Frequency Response: 20Hz–20kHz
• Rack Spaces: 2U
• Power Supply: Standard IEC AC cable