Store demo unit with minor cosmetic marks.

The Warm Audio WA12 MKII Black is a fully discrete, high-voltage microphone preamplifier with 71 dB of gain and dual CineMag USA transformers. Built around a socketed X731 discrete op-amp (a reproduction of the classic Melcor 1731), the WA12 MKII delivers the punchy, focused tone of iconic American console preamps with output attenuation control for driving the signal path into musical saturation.

Op-Amp and Tone Shaping

The X731 discrete op-amp is the warmer predecessor to the modern 2520-style design, delivering clean and lifelike tones at moderate gain and harmonically rich saturation at higher settings. The op-amp is socketed using the standard 6-pin 2520 footprint, allowing replacement with any compatible discrete op-amp for different tonal character. The Tone switch toggles input transformer impedance from 600 to 150 Ohms, adding top-end air and sheen particularly suited to ribbon and darker dynamic microphones. The output attenuation control sits after the CineMag output transformer, enabling the preamp and transformers to be driven into saturation while managing the level hitting the converter.

Connectivity

A front-panel 2 MOhm true Hi-Z input routes instrument signals through the full discrete signal path, including both CineMag transformers and the X731 op-amp. The rear XLR mic input, balanced XLR and TRS outputs, switchable 48V phantom power, -20 dB pad, and polarity inversion handle standard studio recording needs in a compact half-rack desktop format.

Specifications

• Type: Single-channel microphone/instrument preamplifier
• Topology: Fully discrete, high-voltage, dual-transformer
• Op-amp: X731 discrete (socketed, 2520 6-pin compatible)
• Transformers: CineMag USA (input and output)
• Gain: +71 dB
• Tone switch: 600/150 Ohm input impedance
• Pad: -20 dB
• Phantom power: +48V
• Polarity switch: Yes
• Hi-Z input: 2 MOhm (front panel, JFET)
• Inputs: XLR mic (rear), 1/4" Hi-Z (front)
• Outputs: XLR, 1/4" TRS (balanced)
• Metering: LED
• Output attenuation: Post-output transformer
• Power: 115/230V switchable, IEC
• Form factor: Half-rack desktop
• Dimensions: 267 x 216 x 44 mm (10.5 x 8.5 x 1.75")

In the Box

• Warm Audio WA12 MKII (Black)
• IEC power cable