# MUTU – DUAL VCO

A synthesizer with two oscillators in a mutual relationship with each other.



## Goals

- flexible sound-generator
- simple and DIY-friendly
- eurorack-compatible (CV inputs for FM and VCA, size fits eurorack)



## Non-Goals

- No perfect tonal tracking intended
- No features that raise the parts count too much



## Topology

![](images/topology.svg)

## Interface

Panel draft with 16 HP (~80 mm wide, 119 mm tall)

<img src="panel/mutu_panel_top.svg" style="width:340px;" />

### Inputs

| Name       | Function                                                     | Normalization                                    |
| ---------- | ------------------------------------------------------------ | ------------------------------------------------ |
| `CV-VCA-A` | CV-Input for the first VCA. Positive voltages turn up the level of the first oscillator | Fixed positive voltage                           |
| `CV-VCA-B` | CV-Input for the second VCA. Positive voltages turn up the level of the second oscillator | Fixed positive voltage                           |
| `CV-FM-A`  | Frequency modulation (FM) input for the first oscillator     | -                                                |
| `CV-FM-B`  | Frequency modulation (FM) input for the second oscillator    | Signal plugged to the first FM-Input (`CV-FM-A`) |



### Knobs

| Name       | Function                                                     |
| ---------- | ------------------------------------------------------------ |
| `FREQ-A`   | Sets the base frequency (pitch) of the first oscillator      |
| `FREQ-B`   | Sets the base frequency (pitch) of the first oscillator. If `Track` is on, this gets added to the frequency set by `FREQ-A` |
| `MOD-A`    | Changes the amount of frequency modulation (FM) the second oscillator applies to the first |
| `MOD-B`    | Changes the amount of frequency modulation (FM) the first oscillator applies to the second |
| `ATT-FM-A` | Attenuates any incoming (external) modulation signal plugged into the input `CV-FM-A` |
| `ATT-FM-B` | Attenuates any incoming (external) modulation signal plugged into the input `CV-FM-B`. If no signal is plugged into `CV-FM-B` the signal of `CV-FM-A` is used here. |
| `FORM-A`   | Morphs the waveform of the first oscillator between triangle and sawtooth. Might also detune the oscillator |
| `FORM-B`   | Morphs the waveform of the second oscillator between triangle and sawtooth. Might also detune the oscillator |
| `LVL-A`    | Sets the level of the first oscillator. If something is plugged into the CV-input `CV-LVL-A` this knob attenuates the level of the incoming CV-signal. |
| `LVL-B`    | Sets the level of the second oscillator. If something is plugged into the CV-input `CV-LVL-B` this knob attenuates the level of the incoming signal. |



### Switches/Toggles

| Name      | Function                                                     |
| --------- | ------------------------------------------------------------ |
| `S_TRACK` | Switches on or off the tracking function where the second oscillator follows the frequency changes of the first. |
| `S_SYNC`  | Hardsyncs the second oscillator to the first one             |



### Outputs

| Name     | Function                                      |
| -------- | --------------------------------------------- |
| `OUTPUT` | Outputs the summed signal of both oscillators |