The Locomotive Audio 40AM-2 is a two-channel, rackmount tube preamp inspired by classic American designs from the 1940s. Drawing directly from the sonic signatures of the RCA BA-11A and Gates SA-70, it delivers a thick, warm and character-rich tone reminiscent of early broadcast and recording gear. Featuring octal 6SJ7 tubes, premium custom-wound transformers, and user-adjustable tonal shaping controls, the Locomotive Audio 40AM-2 offers engineers the ability to impart authentic vintage colour to a wide range of sources, from vocals to instruments and DI inputs.
At the heart of the Locomotive Audio 40AM-2 are two octal 6SJ7 tubes per channel, one configured as a pentode and the other strapped as a triode, offering up to 52 dB of gain. These are fed by a custom in-house wound MuMetal shielded input transformer and either nickel or steel output transformers, optimised for delivering full-bodied harmonics with exceptional dynamic weight. A 5-position Input Switch allows users to choose between different transformer winding taps, shaping the input’s frequency response and altering the drive level into the tube stage, with both mic (500Ω) and low line input configurations delivering an additional 4.5 dB of gain.
A 5-position Response switch adjusts the overall tonal balance and harmonic texture. Users can enhance top and bottom-end response with position 5 for a larger-than-life sound, or roll off highs and lows with position 1 for a mid-forward tone with subtle harmonic saturation. Position 4 is recommended as a neutral starting point, offering a flatter and cleaner response.
The Level control provides final output trimming and interacts subtly with the response switch, allowing further control over the resulting tonal profile. As output is attenuated, a slight darkening of tone may occur, which can be compensated for by readjusting the response setting. A built-in 20 dB pad and 85 Hz low cut filter expand the unit’s versatility, offering essential control over high-output sources and low-end buildup.
A dedicated high impedance DI input makes the Locomotive Audio 40AM-2 equally suited for electric instruments, and the Line Mode input bypasses the mic circuit entirely, allowing safe connection of external gear without concern for phantom power. The combination of features allows the 40AM-2 to serve as a front-end tone sculptor or re-amplification tool in hybrid studio workflows.
Designed for engineers seeking musical compression, harmonic colour, and full-bodied preamplification, the Locomotive Audio 40AM-2 is a purpose-built tool that honours and evolves the sonic legacy of vintage American broadcast gear. Its rich tonal palette and dynamic flexibility make it a standout choice for those looking to bring authentic 1940s tube character into a modern recording environment.
