Locomotive Audio Model 14B

Locomotive Audio Model 14B is a single-channel vari-mu tube compressor/limiter in its own 2U rack chassis, designed by Eric Strouth as a hybrid of three classic circuits: an input stage close to the Universal Audio 175B/176 (with a slower attack), an output stage related to the Gates Sta-Level/RCA BA-6A, and influence from the Collins 26U. It's one of two standalone (non-500-series) compressors in the Locomotive Audio range, alongside the WT-Comp.

Two operating modes instead of one fixed ratio

A compress/limit switch changes the gain-reduction character from 4:1 in compress mode to 10:1 in limit mode, and disabling compression turns the unit into a pure tube line amplifier. Attack sweeps continuously from 300 microseconds to 20ms, release from 100ms to 2 seconds, covering everything from very fast transient catching to slow, musical dynamics leveling.

Sidechain filter and stereo-link built in

An adjustable sidechain high-pass filter (off, or continuously variable roughly 70-350Hz) keeps the compressor from reacting to the lowest frequencies, and a TRS stereo-link jack ties two 14B units together as a matched pair on a mix bus. Cinemag input and interstage transformers, plus a custom output transformer, round out a tube signal path built on a 6BC8, a 12AY7 and two 6V6 tubes in a push-pull output stage. The option to disable compression and run the 14B as a pure line amplifier adds flexibility for moments in a session where only the tube colour matters, not dynamics control.

KEY FEATURES

• Single-channel vari-mu tube compressor/limiter
• Compress (4:1) / limit (10:1) switch
• Adjustable sidechain high-pass filter
• TRS jack for stereo-linking two units
• Compression-off mode — pure tube line amplifier
• Hardwire bypass
• VU meter: gain reduction / output level
• Designed by Eric Strouth, built in the USA

TECHNICAL SPECIFICATIONS

• Type: single-channel vari-mu tube compressor
• Tubes: 6BC8, 12AY7, 2x 6V6 (push-pull)
• Transformers: Cinemag input and interstage, custom output
• Ratio: 4:1 (compress) / 10:1 (limit)
• Attack: 300µs – 20ms
• Release: 100ms – 2 seconds
• Frequency response: 20Hz – 20kHz
• THD+N: <1%, S/N: >70dB
• Dimensions: 482 x 89 x 254mm (2U)
• Power: 42W, 120/240V AC