Arturia Microbrute User’s Manual
31
Low Frequency Oscillator (LFO)
An LFO is very much like a regular oscillator except that it typically runs at a much lower
frequency. The MicroBrute low frequency oscillator can produce various waveforms at
sub-audio frequencies (0.1Hz up to 200Hz). In general the waveform options are sine or
triangle, sawtooth, and square, waves. The amount, or output level of the LFO can be
controlled before being fed to the target devices to make subtle or wider range sounds.
Envelope Generator
Contrary to an LFO, an envelope generator (or ADSR generator, for “Attack / Decay /
Sustain / Release”) does not provide a repeating pattern but is something that starts at
a certain time, runs its course and then ends. The time that an envelope starts its
sequence of stages is normally triggered by the keyboard, a sequencer or the Gate
input. Pressing down a key or sending a gate signal provides an evolving signal with four
different stages: The ATTACK, DECAY, SUSTAIN and RELEASE
The
attack
stage determines how long it takes for the envelope to go from zero to
its maximum level. The attack time can be as short as 2.5ms or as long as 2.5 seconds.
The
decay
stage begins when the attack stage reaches its maximum value. After
the attack stage is finished the decay takes over and decreases from this maximum
attack level down to a level set by the SUSTAIN parameter. The speed of this decay can
vary from 2.5ms to 2.5 seconds.
The
sustain
stage starts at the end of the decay phase, and remains at the sustain
value as long as a keyboard key is held down or a gate signal remains full on. The
sustain level is variable between zero (no sustain) and the envelope’s maximum value.
With a SUSTAIN value set to the maximum level, you will not hear the DECAY stages
effect because it will not have a level to decay too.