Acustica Audio Releases Ruby – An Official Emulation of The Classic D.W. Fearn Vacuum Tube EQ

New from Acustica Audio, Ruby is as an official endorsement and a faithful representation of the D.W. Fearn highly sought-after vacuum tube equalizer VT-5. 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. The output stage utilizes the same custom Jensen transformer used on the VT-1/VT-2 mic preamps.

Acustica Audio’s plug-ins are based on a unique for the market cutting-edge non-linear Vectorial Volterra Kernels technology. This means that they are build of dynamically captured samples of the original hardware gear. This approach delivers unprecedented sonic quality in the box with very similar micro-details and transient response to the original hardware.

Most of Acustica Audio plug-ins come with a “Preamp on/off” function. With it “on” the plug-in recreates dynamically the pass-through sonic coloration of the original unit (all EQ knobs at 0 gain).

This includes the harmonic distortion behaviour of the hardware, the introduced phase shift and any frequency response deviations. With it switched “off” the plug-in offers a much “cleaner” and more linear sonic character than the hardware.

As with the preamp on gain staging into the plug-in behaves similarly to hitting the original unit at different input levels, Ruby comes with an “Input Trim” control. This allows for a “one knob” internal gain control, by hidden linked input and output gain stages.

When a positive value is selected the signal entering Ruby is brought up by the set amount in dB at the device’s input, and it is brought down by the same level at Ruby’s output. Contrary to this, negative values result in lower internal operational levels compensated at the output of the plug-in.

The “Output Gain” control provided allows for matching the original loudness of the source material after applying equalization.

EQ Section:

  • Low Cut: at 30, 40, 100, or 400 Hz, 0 to -18 dB shelving.
  • Low Boost: 20, 40, 60, or 140 Hz, 0 to 16 dB shelving.
  •  Mid Cut: 200, 300, 400, 500, 600, or 700 Hz, 0 to -16 dB.
  •  High Boost: 1.5, 3, 4, 5, 8, 10, 12, or 16 kHz, 0 to 12 dB with Bandwidth Q of 0.6, 0.8, 1.0, 1.4, or 1.7.
  •  High Cut: 1.5, 3.5, 8, or 28 kHz, 0 to -14 dB shelving.

Preamp Section:

  • Preamp: on and off.

Other controls:

  • Input Trim: from -24 dB to +24 dB.
  • Output Gain: from -24 dB to +24 dB.


  • Challenge-response authorization system allowing activation for two computers per license.
  • The trial version is fully functional for a duration of four weeks. Trial license allows the activation of two computers per license.

Formats supported:

  • Support operation systems: OSX and Windows.
  • Supported plug-in formats: VST2, AAX, and AU.
  • Supported architectures: 32 and 64 bits.

Pricing & Availability:
Ruby commercial version: $235.00 (currently on sale for $199). Available as a digital download immediately after payment.
Ruby Trial version: free 4-week test license.

For more information please visit the Ruby product page.

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