Klavis Terminal 4 is an 8HP Eurorack module that puts a VCA, a low-pass gate and an envelope generator on each of four channels, with a mono/stereo mixer built in. It suits modular users who want amplitude control, LPG tone shaping, envelopes and final mixing in a small footprint, from skiffs to large systems. It can work as a quad VCA, four LPGs, a bank of envelopes or a stereo final mixer, either one role at a time or several at once.
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DC-coupled VCAs: four independent channels or two stereo pairs, handling audio and CV, with Lin/Log response, offset and bipolar level CV
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Three LPG modes per channel: 6 dB/oct single-Vactrol emulation, 12 dB/oct dual-Vactrol West Coast-style LPG, and a 24 dB/oct LPG/VCF hybrid with moderate resonance
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Envelope per channel: eight templates covering ADR, AR, ASR and ADSR, proportional time up to 8 s and adjustable curvature
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Automatic mixing: unpatched outputs are summed into 4>1 or two 2>1 mixes, for audio, external modulation and the internal envelopes
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Stereo tools: linked channel pairs gain a constant-loudness Balance control with bipolar balance CV, plus mono-in to stereo-out
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Recall: settings are saved at power-off and restored at power-on, with six memory slots
The VCAs offer zero-crossing switching, which delays level changes until the waveform passes zero volts to avoid clicks. With some offset dialled in, a bipolar LFO can fully modulate a VCA for tremolo. In Log mode the response behaves much like a mixer fader, attenuating low levels more. Linking channels 1+2 or 3+4 turns the second CV input into a balance input, and if the second input of a pair is left empty, the first is copied to both sides.
When a channel's envelope is active, its CV input becomes a gate/trigger input, and the envelope either drives that channel's VCA or LPG or, with no signal patched in, appears at the output as CV peaking at 8 V. Mixing two channels makes more complex envelopes possible. The manual also covers half-wave rectification, modulation shaping, AND/OR logic and gate or trigger delays.
Five knobs and two buttons are shared across the channels, which you select with four channel buttons. Five white LEDs show when a knob matches its stored value and which way to turn it. The module has a 2 mm aluminium panel, takes firmware updates via audio file and comes in silver or black.