Gratrix Modules for VCV Rack

by Sam Gratrix

Introduction

I've been a fan of polysynths for a while and recently I've had an itch to develop one of my own in software. And then came along VCV Rack with all it's open source VCOs, VCFs and VCAs. So here I am, creating a polyphonic modular synth!

Design Philosophy

When designing these modules I'm working along the following lines:

It should look like and feel like a real Eurorack module.
Were possible generalize to six voice polyphony, even at the expense of lots of wires!
Build on the work of others, especially if I can turn a monosynth into a polysynth.
Learn some stuff along the way. (I'm starting with very little music, synthesis and Eurorack knowledge.)
Try out daft things and have some fun...

Inputs and Outputs

Polyphonic inputs and outputs are arranged in a circle. There wasn't a particularity strong reason to do thus other than I felt it looks like a socket for a six prong plug and I quite like it. Port number one is at 12 o'clock and then they count up in a clockwise fashion.

In a lot of cases the inputs have an additional seventh port in the centre. Should an outer input not be connected, then it will inherit the center input (if it's connected). In other words, it's just a time-saving fanout option resulting in less wiring should you want all inputs to work in the same way.

Modules

I would like to mention that in a lot of these modules I have simply duplicated the work of others to create a poly module out of a mono module.

A module ending with -C is based heavily on a VCV Rack Core module.
A module ending with -F is based heavily on a VCV Rack Fundamental module.
Modules ending with -G vary on how much they use the work of others. Sometimes they may be a modification of something else, or, it may be entirely original design on my part.

Oscillators and Filters

VCO-F1 is a six voice straight clone of Fundamental VCO-1.
VCO-F2 is a six voice straight clone of Fundamental VCO-2.
VCF-F1 is a six voice straight clone of Fundamental VCF.

Amplifiers and Envelopes

VCA-F1 is a six voice straight clone of the Fundamental VCA with a basic mixer to combine the voices to single outputs.
ENV-F1 is a six voice straight clone of the Fundamental ADSR with an additional inverted output.

Faders

FADE-G1 is a two input six voice one-dimensional fader.
FADE-G2 is a four input six voice two-dimensional fader.

Generators

OCTAVE quantises the input to 12-ET and provides an octaves-worth of output with the input value used as the fundamental. Additionally, several whole-octave transpositions of the input are also provided at output.
TODO: I am probably going to redesign this.
CHORD-G1 genearates chords via a CV program selection and a fundamental bass note V/octave input. Upto 12 different chords can be programmed, each with up to six voices.

Interfaces

MIDI-C1 is a six voice straight clone of the Core Quad MIDI-to-CV Interface.
MIDI-G1 is a simplified version MIDI-C1 for those tight on rack space.

Diagnostics

VU-G1 is a simple six input volume monitoring module.
SCOPE-G1 is based on the Fundamental Scope module.
KEYS-G1 is a six input times six voice note monitoring module.

Blanks

Simple do nothing 3-hole high quality blank.
Simple do nothing 6-hole high quality blank.
Simple do nothing 9-hole high quality blank.
Simple do nothing 12-hole high quality blank.

Download

Current release is 0.5.0 and requires VCV Rack 0.5.x:

Mac: Gratrix-0.5.0-mac.zip [670,913 bytes]
Windows: Gratrix-0.5.0-win.zip [3,844,673 bytes]

I hope to add a build for Linux soon. Older releases can be found here.

Source

The source code is avaliable on GitHub.