Macro Parameter
| Property | Value |
|---|---|
| Category | Unipolar / Modulation |
| Voltage Range | 0..+5V (up to +8V) |
| Polarity | Unipolar |
| Bandwidth | DC..~100Hz |
Description
Macro parameters are general-purpose CV inputs that control sound-shaping parameters of a module. The term "macro" emphasizes that a single parameter often affects multiple internal sonic aspects simultaneously.
Typically, the CV is combined with a potentiometer at the module — either analog (op-amp adds pot voltage and CV) or digital (pot and CV are read separately, addition in firmware). The digital method is more flexible for a generic module.
Use Cases
- Control timbre (timbre, harmonics, morph)
- Granular parameters (position, size, density)
- Wavefolder amount
- Filter resonance
- Effect parameters (delay feedback, reverb size)
Eurorack Examples (Mutable Instruments)
- Plaits: HARMONICS, TIMBRE, MORPH — three macro parameters with CV inputs + attenuverter
- Clouds: POSITION, SIZE, DENSITY, TEXTURE — four macro parameters
- Rings: BRIGHTNESS, DAMPING, POSITION
Hardware Implementation
Input Stage: OpAmp → Mux → ADC
- 1% resistors sufficient
- R_in=100k, R_ref=200k, R_fb=33k (standard -5V..+5V stage)
- Anti-aliasing: 470pF across R_fb (f_c ≈ 10kHz) — sufficient for slow modulation
- Clipping note: Signals >5V will be clipped.
Attenuverter Implementation (digital)
In Eurorack, macro CV inputs almost always have an attenuverter (attenuate + invert). Implemented digitally:
- Read potentiometer via separate mux channel
- Apply pot value as scaling factor (-1.0 to +1.0) to the CV
- Add result to base parameter value
Firmware Requirements
- Adaptive filtering (slew limiting): Smooth heavily when change is small (ADC noise/pot jitter), smooth lightly when change is large (real modulation). Better than a fixed IIR coefficient, since fast modulations are not dampened.
- Scaling: Map CV range to internal parameter range (e.g., 0..1.0 or -1.0..+1.0)