Grand Luxe Quad VCLFO
This module consist of four functional blocks:
The VLFCO core is a
modified version of the VCO
from the ASM-1 synth project. It is really a full-fledged VCO, that can
track the keyboard (1 V/oct) and even can be equipped with
temperature compensation. It also has a sync input, which can be
used to synchronize the LFO waveform to note-on, or any other
signal.
The quadrature waveshaper creates a 90 degree phase-shifted
version of the sawtooth waveform. It was developed by myself and
based on an idea by Magnus Danielsson.
With two saw to triangle/sine converters, four waveforms (saw,
pulse, triangle, sine) are available both as normal and 90 degree
shifted versions. That makes a total of eight different waves.
The normal and shifted waves can be used together to create
quadrature effects. But the main reason the shifting feature was
implemented is that I wanted to sync to the zero crossing of the
sine and triangle waves. By using the shifted sine, you can get a
vibrato or wahwah-effect that starts on zero and then goes both
positive and negative.
The waveform selector is employed mainly to cut down on panel
jacks. With it, you can select any two of the eight waveforms. It
is normally controlled by a pot on the front panel. But it could
be connected to any control voltage, like from a sequencer for
instance.
This is a rather complicated circuit. For each LFO there is a tightly packed 160x100 mm circuit board. To have four copies of this powerful module is really major overkill. But I like to keep the user interface consistent, by having four identical rows of contols for all modules where I'll need more than one.
Circuit board layout (PDF-file)
Component placement (PDF-file)
The VCLFO module without any oscillator boards.
The module seen from below. Front panel graphics not yet in place.
