Animal Factory Orobas


Orobas is a dual tube amplifier that is composed of two identical units.

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Selected by Music Radar as one of the best Eurorack/modular releases at Winter NAMM 2020, this tube VCA took Animal Factory back to its origins as a tube amp builder. Two identical VCAs that can be connected in parallel, mono to dual mono or series. Full range amplification for thick bass, tubes operating at medium voltages so that control voltages have a noticeable effect on tonal characteristics.

The signal routing possibilities and control offered by this module will open up a ton of usage possibilities – use it as a dual 4-channel tube mixer, or an end stage saturator, for mild saturation or for severe wave-folding. The characteristics of this tube make for one unique VCA. Add the CV-controllable feedback loop to the mix and you will very likely (we don’t guarantee this though) open up dark portals of cosmic influence and summon goetic demons into your life.

The first batch of Orobas will ship, as far as stocks last, with NOS American (RCA, or manufactured by RCA under a different brand name) 6SJ7 tubes. The circuit runs them at approximately 65V, well below their regular operating voltage of 300V, effectively extending their lifespan tremendously


Each channel has two audio inputs with dedicated gain controls and one output volume control.
Thanks to clever routing, a wide variety of sounds can be created. The two channels can be connected in parallel or in series (Parallel / Series). In series connection, the output of channel 1 is still active, good for parallel signals (note: each channel output is phase-inverted in relation to the opposite input). This way, feedback can be generated by feeding back the signal from output 1 to e.g. a control voltage input.

The screen control voltage input determines the gain and the sound characteristics. Additionally, the input is normalized to INPUT 1 of the respective channel.

The Suppress control voltage input is normalized to the input signal if nothing is connected. The purpose of this input is to direct electrons reflected from the anode back to the anode. Turning the knob to the positive does not change as much, turning it to the negative slightly attenuates overtones. With a positive control voltage the change is minimal, but with a negative control voltage you can realize e.g. ducking effects and effectively switch off the tube. Audio Rate Modulation is also possible here and a bit milder than with the Screen CV, but still effective.

The evocation potentiometer controls the feedback of the second output into the first channel. The sonic performance is very much dependent on the Plate Bias switch. The Plate Bias switch effectively controls the headroom. This allows you to use the tubes in three different settings, from fuzz sound to full distortion.

Tube Length: 55 mm

    • 100 mA +12V
    • 40 mA -12V
    • 0 mA 5V
    • 45 mm deep

Additional information

Weight 0.35 kg
Dimensions 30 × 15 × 10 cm