Locomotive Audio Copperline

Locomotive Audio Copperline isn't a preamp or a compressor, it's a two-channel signal-conditioning tool that sits between a microphone and a preamp, or between two line-level devices. Instead of amplifying or colouring the sound, it manages phantom voltage, level, filtering and polarity before the signal moves further down the chain. It's the only device of this type in the Locomotive Audio catalogue, the rest of the brand's range is preamps, compressors and DI boxes.

Adjustable phantom power instead of a fixed +48V

A patent-pending phantom power source, adjustable up to 52V, ramps up over 5 seconds on turn-on, protecting older, delicate ribbon and tube microphone transformers from a voltage spike at startup. For microphones that want something other than standard phantom, that's a function a typical single-voltage preamp doesn't offer.

An attenuator, a filter and a vintage load in one module

A 5-position attenuator (Unity, 15, 20, 30, 40dB) and a 5-position high-pass filter (off, 45, 75, 150, 300Hz) on a mu-metal shielded inductor give control over level and low-end content before the preamp even sees the signal. A polarity switch, a mute that works independently of every other setting, and a "Vintage Ω" load, an 825Ω resistor switched across XLR pins 2 and 3, simulate the low-impedance input of older gear. It's particularly useful when working with older ribbon or tube microphones that are sensitive to standard +48V, or when building a custom signal chain ahead of a specific preamp.

KEY FEATURES

• 2-channel mic/line signal-conditioning module
• Adjustable phantom power up to 52V, 5-second ramp (patent pending)
• 5-position attenuator: Unity / 15 / 20 / 30 / 40dB
• 5-position high-pass filter: off / 45 / 75 / 150 / 300Hz
• Polarity switch and independent mute
• "Vintage Ω" load (825Ω across XLR pins 2/3)
• Mu-metal shielded inductor in the filter path
• Hand-built in the USA

TECHNICAL SPECIFICATIONS

• Type: 2-channel mic/line conditioning module
• Phantom power: adjustable, up to 52V, 5-second ramp
• Attenuator: Unity / 15 / 20 / 30 / 40dB
• Input impedance at 15-40dB: 1200-1500Ω
• High-pass filter: off / 45 / 75 / 150 / 300Hz
• "Vintage Ω" load: 825Ω (XLR pins 2/3)
• Connectors: XLR in/out per channel