Fairi-Mu Mojo Module Settings

The Locomotive Audio Fairi-Mu Module is a stereo vari-mu style compressor that can be used as a stereo or dual mono processor. The only feature on the module that is permanently linked is the adjustable threshold. Otherwise, all other features are independently customizable.

There are multiple jumpers and trimmers on the board that allow you to customize how the module will affect your audio.


Trimmers P1 & P2: Left Channel (P1) and Right Channel (P2) Make-up Gain – These are calibrated at the factory to offset typical levels of gain reduction with the default threshold setting.

Trimmers P3 & P4: Left Channel (P3) and Right Channel (P4) Tube Balance – These are calibrated at the factory to adjust each tube’s internal balance between triodes. Balanced tubes will cancel out gain reduction sidechain voltages so they are not audible. It is not recommended to readjust these trimmers unless after changing tubes. 

Trimmer P5: Threshold – turn clockwise to raise the threshold for less

compression and more saturation. Turn counter-clockwise to lower the

threshold for more compression and less saturation. By default we set this to its

midpoint. Lower threshold will lower maximum gain reduction ratio and higher threshold will increase maximum gain reduction ratio.

Jumper J1 & J2: Release Right (J1) and Left (J2) – 0.1, 0.3, 0.5 s

Jumper J3 & J4: Attack Right (J3) and Left (J4) – 1, 10, 40 ms, Compression OFF

Jumper J6 & J8: Sidechain High Pass Filter frequency Right Channel (J6) and Left Channel (J8) – Full, 100, 200 Hz; the bottom end will sound less compressed with higher frequency settings

Jumper J10: Stereo Link – when off left and right channels will compress indepentently from each other. When on compression from one channel will trigger compression in the opposite channel.

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