CV Input Signal Types #19 — Slew/Glide CV
| Property | Value |
|---|---|
| Category | Special |
| Voltage Range | 0..+5V |
| Polarity | Unipolar |
| Bandwidth | Low-frequency (LFO rate) |
Description
Slew/Glide CV controls the portamento time between notes (glide) or the transition speed of a slew limiter. Higher voltage = longer transition (or vice versa, depending on implementation).
Although often considered a "DC" signal, Eurorack users regularly patch LFOs or envelopes into glide inputs to dynamically vary the portamento time per note.
Use Cases
- Control portamento time (slow gliding between notes)
- Vary slew rate of a parameter
- Influence legato behavior via CV
Eurorack Examples (Mutable Instruments)
- Stages: In glide mode, a parameter value controls the slew rate
Hardware Implementation
Standard Input Stage: OpAmp → Mux → ADC
Identical to generic unipolar CV. No special precision requirements.
Firmware Requirements
- Exponential scaling: Slew times should be mapped exponentially (e.g., 0V = 1ms, 2.5V = 100ms, 5V = 10s). Linear scaling feels unmusical.
- Sample rate: ~1kHz sufficient. Signal must however be smoothed via software low-pass (IIR) to prevent "zipper noise" (audible stepping) when modulated by LFOs.