User's Manual

4.4. VCF (Voltage Controlled Filter) filters the sound
Next comes the VCF, where the real fun begins. The VCF has the power to “open or shut” the
low-pass filter, depending on the settings of the VCF's CUT Control and the input from either
ENV-1 or ENV-2 as selected by the 2-position switch between them. Like the Oscillators, the
VCF can receive LFO modulation either directly, or via the MOD wheel.
4.4.1. The difference between HPF CUT and VCF CUT
The most common misunderstanding of the filter section of the Jupiter 8 involves the two
CUT faders that are right next to each other:
• When the HPF CUT fader is all the way down, the filter is wide open and is
essentially bypassed.
• The VCF CUT control is the opposite: it’s wide open when its fader is all the way
up.
This apparent contradiction is because the two CUT controls are not “level controls”, they
are crossover frequency controls. When VCF CUT is at the bottom, it rolls off all frequencies
above 20 Hz…which shuts the audio path down entirely (unless one of the modulators opens
the filter).
Which leads to another common question from first-time programmers: “How come the
VCF MOD control doesn’t seem to affect the sound at all? How can I get that filter sweep
sound?” The answer is simple: When the VCF CUT control is at maximum, the filter is almost
wide open, so opening it further with modulation has very little effect. Lower the VCF CUT
fader until you hear the effect you want.
4.4.2. Envelope choice and Resonance (RES)
The switch between the envelopes and the VCF lets you select which envelope controls the
filter. In the ENV-1 position, the VCF can follow a different curve from the VCA; in the ENV-2
position, the VCF follows the same envelope that controls the VCA.
The RES control of the VCF stands for Resonance. A resonant filter has a “peak” or resonance
that emphasizes the frequency at the pass point; at a high resonance, it is so close to feeding
back that it is like another tone generator. (In some synths, the resonance can go into total
feedback and generate a sine wave; the Jupiter stops short of that point.)
4.5. VCA (Voltage-Controlled Amplifier) controls the
amplitude of the sound over time
The last stage in the audio path is the VCA, which is usually triggered to open and close by
ENV-2. The VCA's default setting is off. If it's not opened by a modulator (either ENV-2 LVL or
LFO MOD), no audio signal will pass through to the output.
31 Arturia - User Manual Jup-8 V4 - How Analog Synthesis Works