The Befaco Slew is a 4 HP Eurorack module that limits how fast a voltage can change and detects whether a signal is rising or falling. It suits modular users who want portamento or acid-style slides on stepped sequences, with separate glide speeds for rising and falling notes. It also handles general CV smoothing and gate-to-envelope tasks.
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Independent rise and fall faders: one-hand control of both slew times. Raising a fader lengthens the slew.
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Three-position range switch: selects fast, medium or slow time ranges.
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Shape control: runs from linear slew to a response where larger jumps glide faster, for time-compensated portamento.
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Voltage-controlled slew time: a 0 to 10 V CV input can be routed to rise, fall or both.
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Slope detector: dedicated RISE and FALL gate outputs fire while the output is moving up or down.
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Accurate pitch tracking: tracking error under 1 mV.
In practice the Slew sits between a sequencer and an oscillator to add glide. It accepts any CV from -10 to +10 V, so it can just as easily smooth stepped modulation or tame abrupt changes elsewhere in a patch. Feed it a gate and the rise and fall faders act as attack and release times, giving a simple Attack-Sustain-Release envelope.
When a CV is patched in, the rise and fall faders become attenuators for that input. That makes it easy to modulate one slope while keeping the other under manual control.
The slope detector reads the output, so its sensitivity follows the slew time. At the fastest settings it reacts to very small movements. If ripple in the incoming signal produces unwanted gates, a longer slew time cleans this up. The RISE and FALL gates can trigger events whenever a voltage moves in either direction.
The Slew is designed in Barcelona by Befaco. This listing is the assembled module.