Ruby is a faithful representation of the D.W. Fearn’s highly sought-after vacuum tube equalizer VT-5, and is officially endorsed by Fearn himself. The original hardware equalizer uses passive LC circuitry with class-A triode vacuum tube stages for the input and output. The input transformer is made by Jensen, and the output stage utilizes the same custom Jensen transformer that is used on the VT-1/VT-2 mic preamps.

The preamp stage dynamically recreates the pass-through sonic coloration of the original hardware unit, which includes the harmonic distortion behavior of the hardware, the inherent phase shift, and the frequency response deviations. When the preamp is switched off, the plugin offers a cleaner and more linear sonic character than the original version.

Gain staging into the plugin behaves similarly to hitting the original unit at different input levels, which is why Ruby comes with an "input trim" control. This allows for one-knob internal gain control by means of hidden linked input and output gain stages.