Signal Types

Every jack in Soba has a signal type, and every type has a color. The color of a jack tells you what it sends or expects, and a cable takes the color of the output it comes from, so you can read a patch's signal flow at a glance.

Type	Color	Range	Carries
Audio	Blue	−1.0 to 1.0	Sound
Control	Orange	0.0 to 1.0, or −1.0 to 1.0	Modulation and pitch (CV)
Gate	Green	0.0 or 1.0	Notes, clock pulses, triggers
MIDI	Purple	Note and controller events	Reserved; see MIDI
Bus	Pale steel	A whole stereo mix and its sends	A Mixer's Chain Out into the next Mixer's Chain In; see Bus

Underneath, audio, control and gate signals are all the same thing: a stream of numbers at the audio sample rate. The type describes what the numbers mean, and it decides which jacks a cable may connect (see Which types connect).

Audio

Audio is the sound itself: a waveform swinging between −1.0 and 1.0, at your audio device's sample rate (typically 44.1 or 48 kHz). Oscillators make it; filters, the VCA, the Mix, the Mixer and the effects shape it; the Audio Output sends it to your speakers.

Keep audio within ±1.0 and it passes through the output untouched. Louder than that and the output stage's limiter, on by default, catches the peaks before they clip. It's a safety net, though, not a mixing tool. When several voices or oscillators add up, bring the level down with a VCA or the Mixer.

Control

Control signals, often called CV (control voltage), move a parameter instead of making a sound. They come from envelopes, LFOs, the sequencer and Note In, and they go into jacks such as a filter's Cutoff or an oscillator's FM.

A control signal is either:

Unipolar, from 0.0 to 1.0. An envelope is unipolar: it rises from nothing to its peak and falls back.
Bipolar, from −1.0 to 1.0. An LFO in bipolar mode swings both ways around the center, which suits vibrato or a sweep around a set cutoff.

Most control signals change slowly, but nothing stops them running at audio rate. Patch an oscillator into another oscillator's FM input and you have FM synthesis.

Pitch: 1 per octave

Pitch travels as a control signal on a 1-per-octave scale, the digital version of the 1 V/octave standard in hardware modular. Each 1.0 is an octave:

Pitch CV	Note (with the oscillator's tune knobs at 0)
−1.0	C3
0.0	C4 (261.63 Hz)
0.5	F♯4
1.0	C5
2.0	C6

One semitone is 1/12. The Pitch outputs of Note In and the Step Sequencer both use this scale, so they play an Oscillator in tune with nothing to calibrate. Both filters take their Cutoff CV on the same scale, so a pitch cable patched into Cutoff makes the filter track the keyboard exactly.

Gate

A gate is either on (1.0) or off (0.0). It says when: a key held down, a step in a sequence, a tick of the clock. The ADSR Envelope, for example, starts its attack the moment its Gate goes on (the rising edge) and starts its release the moment it goes off (the falling edge).

A short gate is often called a trigger. Modules that only care about the moment a gate begins, such as the clock input of the Step Sequencer or the Trig input of Sample & Hold, treat both the same way.

Gates come from the Gate outputs of Note In, the Clock and the Step Sequencer (which also has an EOC, end-of-cycle, gate).

MIDI

MIDI is the purple signal type, and today no jack uses it. MIDI from your controller doesn't arrive over a cable. It goes straight into the modules that listen for it: Note In and the MIDI Monitor. Note In turns notes into ordinary Pitch, Gate and Velocity signals that the rest of the patch understands, and does the same for your computer keyboard.

Bus

Bus is the pale steel signal type. One Bus cable carries a Mixer's whole mix and its sends from its Chain Out to the next Mixer's Chain In, so Mixers can be chained for more than four channels. It connects only to another Bus: no audio, control or gate jack takes it, and a Bus jack takes nothing else.

Which types connect

Same-type connections always work. A few cross-type connections work too, and the rest are refused:

From	To	Allowed?	Why
Audio	Control	Yes	Audio-rate modulation, such as FM
Control	Audio	Yes	Mix or process a CV like audio, such as an LFO into the Mix
Gate	Control	Yes	Use a gate as a 0-or-1 modulation signal
Gate	Audio	No	A gate needs an envelope or VCA to become sound
Audio or Control	Gate	No	Gate inputs only take gates
MIDI	Anything else	No	MIDI needs a converter module

Allowed cross-type connections pass the signal through unchanged. An audio cable into a control input is the raw waveform; a gate into a control input is exactly 0.0 or 1.0.

If you drop a cable on a jack that can't take it, Soba removes the cable and the status bar at the bottom of the window explains why, for example Control cannot connect to Gate.

Signal color and category color

Don't confuse the two palettes. Jacks and cables are colored by signal type, as above. The bar across the top of each module is colored by the module's category: blue for Sources, teal for Filters, and so on. See the Module Overview.

Soba Documentation