Figure 5 shows the opposite state; the
Cycle
button is initially on, so the incoming gate signal stops the
cycling for as long as the gate is high. In this case, as the pulse width of the gate signal gets wider,
there are longer pauses between groups of envelopes.
Note that the first pulse in Figure 5 does not stop the envelopes, and the three rapid pulses in Figure 4
only cause one envelope. This illustrates an important aspect of the
Dual EnvVCA
: the state of the
Cycle
jack and button only matter when the envelope is stopped (at 0V). Any combination of gates and
button presses while the envelope is running have no effect; it’s only when the envelope finishes
running that the
Cycle
jack or button can make it cycle again.
Follow Jack With Gates
Figure 6 illustrates the use of gates on the
Follow
jack. A gate signal will cause the envelope to rise as
long as the gate is high. When the gate goes low,
the envelope will fall.
The fourth gate in Figure 6 shows that if the gate is
held high while the envelope reaches its maximum,
the envelope will hold (sustain) until the gate is
released. This is an easy way to create an ASR
envelope (Attack Sustain Release).
The short burst of pulses at the end illustrates how
the
Follow
jack can be utilized to create complex
envelope shapes using only a sequence of gates.
The
Follow
jack can be used with more than gates, see the next section for a detailed discussion.
Fundamentals of the Follow Jack
The
Follow
jack causes the envelope to rise or fall in order to “follow” the signal on the jack. Sending a
high voltage (5V) into the Follow jack will cause the envelope to rise. Sending a low voltage (0V) will
cause it to fall. This can be seen in Figure 6 of the previous section.
Sending voltages between 0V and 5V, such as a waveform from an LFO, or an audio signal will have
more complex effects.
There are two basic rules that govern this jack:
Rule 1:
If the voltage on the
Follow
jack is greater than the envelope voltage, the envelope will
rise; if the voltage on the
Follow
jack is less than the envelope voltage, the envelope will fall.
That is, the envelope will always “seek” the
Follow
signal: it will go up if the
Follow
signal is higher,
and it will go down if the
Follow
signal is lower. This is where the term “follow” originates.
Rule 2
: The envelope can only rise and fall at the speed set by the
Rise/Fall
controls and CV.
This means that if the
Follow
jack suddenly jumps up (for example, when a gate is applied), the
envelope will try to follow that jump by rising, but it can only rise as fast as the controls allow it. The rate
of change, or slew, is limited, thus we call the
Follow
circuit a “slew limiter”.
Note that the term “envelope voltage” in Rule 1 refers to the internal envelope voltage, before the
Level
and
Offset
knobs and
Env Out
jack output driver. Internally, the envelope has a maximum of 5V and
minimum of 0V, which is why the
Follow
jack only responds to voltages from 0V to 5V. The
Env
Out
jack’s output driver doubles the internal voltage, so a 5V internal envelope corresponds to
approximately 10V envelope on the jack.
Armed with these two basic rules, we can now showcase some advanced uses for the
Follow
jack in
the following sections.
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Figure 6: Sending gates into the Follow jack. When the
input gate goes high, the envelope rises; when the input
goes low, the envelope falls.
