3
Interpole
Structure and Overview
A ”voltage controlled” amplifier module
(VCA) follows the filter. The amplifier is
also controlled by the envelope and LFO.
Envelope control can be switched off so
that the LFO/VCA can serve as a tremolo
or autopanner.
Thanks to the Circuit Modeling process,
the audio is faithfully rendered and free of
aliasing. Those familiar with aliasing know
that it produces unpleasant and unnatural
sounding analog signals. Interpole’s
various modulation effects and the resulting
audio quality profit from this unique
process. Often various distortions or
sidebands fill out the full range of the
spectrum as a result of heavy or wild
modulations (such as frequency
modulation). Alias-free rendition is
absolutely necessary for producing such
spectra. After working for a while with new
sounds you will come to appreciate this
characteristic.
No less important than the envelope stage
is the LFO. It features six modulation
waveforms, and synchronization to MIDI
clock if desired. Individually adjustable
intensities are available for filter frequency
and amplitude modulation. In
link mode,
the LFO switches the signal from the first
channel to the second, with optional
modulation inversion on the second
channel, to produce stereo-filter autopan
effects. By restarting the LFO with MIDI
triggers or by modulating the LFO rate with
an envelope, the LFO modulation becomes
even more complex and lively.
But it is the filter that performs the most
impor tant task: the actual signal
processing. In addition to the standard cut-
off and resonance parameters, the filter
also provides a
Drive parameter to
introduce distortion that produces effects
from gentle saturation to heavy distortion
with strong resonance—everything you
could ask for in a filter. The filter is
controlled by the envelope and/or the LFO.
With appropriate configuration all kinds of
exciting stereo filter effects can be
produced.
Interpole is a stereo effect consisting of
two identical sections, left and right, for
the processing of any audio signal. Each
section consists of an envelope follower
or ADSR envelope generator, an LFO, a
lowpass filter, and a VCA. The two sections
can operate independently or in tandem in
link mode so that the filter can be used to
process either two mono signals or one
stereo signal.
Interpole is more than a simple effect: think
of it as a synthesizer in which the
oscillators are replaced by external signals.
The envelopes and LFOs control the filter
and the VCA just as in a synthesizer.
One of Interpole’s most important features
is the envelope section. The envelope
section can operate in one of two modes:
”Env” or ”Gate”. In Env mode the section
implements an envelope follower. Gate
mode implements an attack-decay-sustain-
release (ADSR) envelope generator which
can be triggered by a Threshold or via MIDI.
The envelope can modulate filter
frequency, amplitude, and LFO rate.
