The Locomotive Audio Model 86B-2 is a two-channel, transformer-coupled tube microphone preamp, instrument DI and line-level colour processor. With up to 75 dB of gain, selectable microphone impedance, independent Gain and Level controls, 48 V phantom power, line re-amp mode and variable harmonic drive, it covers pristine detail, rich tube warmth and aggressive saturation from the same 2U unit.
 
The Locomotive Audio Model 86B-2 is a dual-channel tube preamp designed for engineers who want more than one fixed preamp sound. Inspired by 1950s American valve circuitry and the Ampex 601 lineage, it combines high-gain microphone amplification with flexible drive control, transformer colour, front-panel instrument inputs and dedicated line-level processing. It can capture a source with clarity and depth, add controlled tube density during tracking, or be used after conversion to re-amp DAW stems through tubes and transformers.
 
Each channel uses an EF86 input tube and a 12AY7 output tube. This combination provides up to 75 dB of gain while maintaining the characteristic harmonic weight, dimensionality and responsiveness associated with classic tube recording equipment. MuMetal-shielded input transformers reduce hum sensitivity, while nickel-and-steel output transformers contribute to the preamp’s broad, solid tone and output authority. The two channels are fully independent, allowing the 86B-2 to work as a stereo front end, two separate mono mic preamps or a flexible combination of microphone, DI and line processors.
 
The key to the 86B-2 is the interaction between the Gain and Level controls. Gain determines how hard the tube and transformer stages are driven; Level compensates the output after the desired amount of drive has been selected. Use conservative Gain with appropriate Level for clean, open tube amplification. Increase Gain and reduce Level for thicker harmonics, denser midrange, gentle tube compression and increasingly assertive saturation. This makes the 86B-2 valuable when a source needs subtle warmth, pronounced vintage personality or a more aggressive, grungy edge.
Each channel has a four-position input selector:
 
Mic 500 Ω for a lower input impedance and a different microphone loading relationship
Mic 1.8 kΩ for a more conventional microphone-preamp impedance
Line 10 kΩ for processing DAW outputs, synths, drum machines and other line-level sources
DI 1.6 MΩ for guitar, bass, piezo pickups and high-impedance instruments via the front-panel input
 
The selectable mic impedance is useful for tailoring the interaction with dynamic, ribbon and certain condenser microphones. It can subtly influence level, transient response and tonal balance before any gain or saturation is added. The dedicated rear-panel XLR line inputs are separate from the microphone inputs, so line-level signals can be connected and processed without the risk of accidentally applying phantom power to external equipment.
 
The 86B-2 includes +48 V phantom power, a 20 dB pad, polarity inversion and a 100 Hz high-pass filter on each channel. The pad increases input headroom for loud sources, while the high-pass filter helps reduce stand-borne vibration, rumble, air-conditioning noise and excessive proximity effect before the signal reaches downstream converters or compressors. The polarity switch is useful for multi-mic setups, DI-plus-amplifier recording and any situation where phase alignment needs correction.
 
For line processing, the dedicated Line mode transforms the 86B-2 into a dual-channel tube re-amp and colour stage. Route stems, virtual instruments, stereo keyboards or mixes from your converters into the separate line inputs, drive the EF86/12AY7 stages to taste, then return the transformer-coupled output to the DAW. This is particularly useful for bringing dimensionality and analogue harmonics to digitally produced material without committing to tube colour while tracking.
 
The three-colour output LED helps maintain sensible gain staging: green indicates levels above −10 dBu, orange above +10 dBu and red above +18 dBu. With a maximum output level of +24 dBu, the 86B-2 has the headroom needed to interface confidently with professional converters and analogue hardware. Its heavy 16-gauge steel chassis, balanced XLR outputs and switchable 115/230 V mains operation make it suitable for permanent studio installation, mobile recording rigs and professional hybrid systems.
 
The Locomotive Audio Model 86B-2 is therefore not simply a dual tube preamp. It is a flexible analogue front end: two premium microphone preamps, two instrument DIs and a stereo line processor in one rack space-efficient 2U chassis. It suits engineers who want a convincing tube foundation for vocals and acoustic instruments, but also need an outboard colour tool for drums, guitars, bass, synths and DAW mixes.
 
Key features
Dual-channel tube microphone preamp, instrument DI and line colour processor
Inspired by 1950s American tube-preamp topology and Ampex 601 lineage
One EF86 input tube and one 12AY7 output tube per channel
Up to 75 dB of gain per channel
Independent Gain and Level controls for clean amplification or harmonic drive
Two selectable microphone input impedances: 500 Ω and 1.8 kΩ
Dedicated 10 kΩ line-level XLR inputs
Front-panel 1.6 MΩ Hi-Z instrument input on each channel
Separate rear mic and line XLR inputs
+48 V phantom power per channel
20 dB input pad per channel
Polarity reversal per channel
100 Hz high-pass filter per channel
MuMetal-shielded input transformers
Nickel-and-steel output transformers
Tube re-amp mode for DAW stems, virtual instruments and line-level sources
Three-colour output LED metering
Maximum output level: +24 dBu
Balanced XLR outputs
Heavy 16-gauge steel 2U rackmount chassis
Switchable 115 V / 230 V AC operation
Handmade in the USA
Lifetime manufacturer warranty on parts and workmanship
 
Applications
Vocals with detailed, warm or saturated tube character
High-gain amplification for dynamic and ribbon microphones
Acoustic guitar, piano, strings and percussion recording
Drum tracking with clean headroom or driven tube harmonics
Direct guitar and bass recording through the front-panel DI
Adding valve density to synths, drum machines and keyboards
Processing DAW stems through tubes and transformers
Stereo re-amping for mixes, buses and virtual instruments
DI-plus-amplifier recording with polarity control
Building a compact high-end recording front end with two flexible channels