The OpticTone MK2 is an enhanced version of our original module, combining a 12dB multi-mode Vactrol VCF and a Vactrol VCA. This unique circuit is inspired by the distinctive characteristics of Vactrols and Lowpass gates, known for their smooth and natural sound.

The Filter section provides the three essential filter types: Lowpass, Bandpass, and Highpass. A new Range Switch lets you choose between high, mid, and low filter ranges, with the High setting offering the widest filter range. The Resonance knob, featuring a voltage control input, delivers enhanced modulation flexibility. The feedback knob interacts with the Resonance path, acting as a resonance compensation control, allowing you to adjust from smooth, creamy resonance to intense self-oscillation.

The OpticTone MK2 adds a new switch to select between series and parallel configurations for the VCA and Filter. In parallel mode, the VCA comes first. Both the VCA and Filter are controlled by the Freq/Amp knob, its voltage-control input, and touch control via the three lines on the panel below the knob. The signal combination can be crossfaded using a dedicated knob.

The new circuit is designed to enable users to create low pass gate pluck sounds. To achieve Lowpass gate pluck sounds, send a short trigger (about 20ms) to the Freq/Amp CV input and use the Vactrol’s slow, envelope-like decay. You can use the crossfade knob to blend the VCA and VCF signals, allowing you to balance and fine-tune the pluck effect.

The Frq switch inverts the filter frequency control, causing the filter to “close” when the VCA is “opening,” and vice versa.
The Ping input lets you generate the distinctive percussive sounds typical of vactrol filters. Pinging a filter involves sending a short trigger or gate signal to the filter, causing it to briefly resonate and produce a percussive sound. This technique is commonly used in modular synthesis to create drum-like or plucked sounds. The Ping frequency is controlled by the Freq/Amp knob, offering a wide range of tones from deep kick drums to high-pitched bongos.
The module also includes a pre-filter Drive knob, providing a range of sonic textures from subtle warmth to heavy distortion, adding rich harmonic content to your sound.

Features:

• Vactrol-based 12dB multi-mode Voltage Controlled Filter: Lowpass, Bandpass, and Highpass.
• Vactrol-Based Voltage Controlled Amplifier.
• Crossfade knob to blend the VCA and VCF sections.
• Voltage-controlled Resonance.
• Improved circuit for Lowpass Gate pluck sounds.
• Ping Input for generating percussive sounds.
• Filter Range switch.
• Switch to set VCA and VCF in Parallel or Series.
• Filter Frequency polarity inversion switch. Does not change VCA polarity.
• Overdrive and Feedback controls.
• Attenuator/inverter knobs on all voltage-controlled inputs
  Touch control over Frequency and Amplitude.

Specs:

• Width: 10HP
• Depth: 33mm
• Power consumption: 55mA +12 / 55mA -12
• Eurorack Format
• Doepfer power connection

Check the OpticTone MK2 manual here