Store demo unit with minor cosmetic marks.

The Warm Audio WA273 is a dual-channel, Class A microphone preamplifier that recreates the 1073-style British console preamp. Featuring hand-wired construction with custom Carnhill UK input and output transformers and 80 dB of gain per channel through a fully discrete signal path, the WA273 delivers the rich, warm analog tone heard on classic recordings by The Beatles, Led Zeppelin, and U2.

Carnhill Transformers and Build

Warm Audio worked directly with Carnhill Transformers of Cambridgeshire, UK, to reproduce the earliest and most coveted transformer designs used in vintage 1073 consoles. These custom-wound transformers saturate smoothly when driven, contributing the fluid, musical character that defines the British preamp sound. The WA273 is hand-wired and hand-assembled, with through-hole PCB components populated by hand. Tantalum and polystyrene capacitors in the signal path and a carefully selected output transistor maintain fidelity to early British designs, delivering smoother performance in high-gain settings than typical modern reproductions.

Controls

Each channel provides a 22-position resistor-stepped gain switch with 80 dB of range, a Tone button that toggles input transformer impedance between 1200 and 300 Ohms, and a four-position inductor-based high-pass filter at 50, 80, 160, and 300 Hz. Unbalanced send/return insert jacks on each channel allow patching in external compressors or EQ before the output transformer. 48V phantom power, polarity inversion, and ground lift are switchable per channel.

Specifications

• Type: Dual-channel, Class A, 1073-style British mic/line/instrument preamp
• Topology: Fully discrete, hand-wired, hand-assembled
• Transformers: Carnhill UK (custom, input and output)
• Gain: 80 dB (resistor-stepped)
• High-pass filter: 4-position (50, 80, 160, 300 Hz)
• Tone button: Switches input transformer impedance (1200/300 Ohms)
• Phantom power: +48V per channel
• Polarity switch: Yes
• Ground lift: Yes
• Inputs per channel: XLR mic, TRS line, TS instrument, TS insert send/return
• Outputs per channel: XLR, TRS
• Frequency response: 20 Hz - 20 kHz (+/- 0.5 dB)
• Power: 115/230V, internal IEC
• Rack size: 1U, 19"

In the Box

• Warm Audio WA273
• IEC power cable