Oscillators 1&2 Mod/Sync. Section - Novation Bass Station Rack Owner's Manual

HOW THE CONTROLS WORK
Oscillator 1 &2 Mod/Sync. Section
This section allows you to setup modulations (automat-
ic changes) to the pitch timbre of the oscillators whilst
they are playing back. This gives the sound more "life",
by making it more interesting to the ear. Pitch changes
include the amount of vibrato and auto bends or slides.
Timbral changes are achieved by varying the pulse
width and thereby the harmonic content. You can also
set the oscillators to syncronise.
Oscillator 1 2 - Switch
This switch selects the oscillator whose modulation you are currently setting. Any
changes you make to the three knobs and the 'PWM Source' switch will be applied to
whichever oscillator is currently selected. When you switch to the other oscillator, you
will need to alter the positions of the knobs and switches in this section to make their
current positions apply to the new oscillator, otherwise the previous settings will still
apply.
Envelope - Rotary
This knob controls the amount of pitch modulation to the currently selected oscillator
(see above) from envelope 2. In the centre position there is no effect on the oscilla-
tor's pitch, to the left the effect is negative (ie. the pitch drops and then rises) and to
the right positive (the pitch rises and then falls). The further you set the knob from the
central position the further the pitch rises and falls. See the "Envelope Section" later
for the exact programming of the rise and fall times.
LFO -Rotary
This knob controls the amount of pitch modulation to the oscillator. ie. how much
above and below the set pitch the oscillator regularly rises and falls. If the LEO is set
to Triangle wave and it's speed is above the centre of its range. then this will normally
produce a vibrato effect, but other effects like a siren or seagull cries are possible with
more extreme settings. See the LEO section on page 12 for more details on adjusting
the LEO parameters to create these effects.
Pulse Width - Rotary
This knob has a direct effect on the Pulse Width when the waveform of the selected
oscillator is set to Pulse (Square). When the Mod Source switch is set to Manual, the
position of this knob controls the actual width of the Pulse. At the far left, the Width is
50% (ie. minimum and maximum values are of equal length) giving a special case
which we refer to as a square wave, which contains all the odd-numbered harmonics
giving a 'hollow' sound reminiscent of a clarinet. As you move the knob to the right the
Pulse Width gets narrower and more and more high harmonics are added at the
expense of the fundamental pitch giving the sound a thin, trebly quality. At the far right
the fundamental has almost disappeared and the sound becomes very thin indeed.
When the Mod Source switch is set to Env 2 or LEO, this knob governs the amount of
variation in the pulse width in a negative or positive direction about a central 'off posi-
tion. As the knob is moved to the left, the variation in the Pulse Width will increase
progressively in a negative manner whilst moving it to the right will vary the Pulse
Width in a positive manner.
PWM Source - Switch
This switch selects how the Width of the Pulse Wave (if selected on either or both
oscillators) is controlled. In the MAN (manual) position, the width is directly controlled
by the position of the Pulse Width knob above. In the ENV 2 position, the variation in
the Pulse Width is controlled by the second Envelope, starting and finishing at 50%
with the amount of shift away from this setting being controlled by the Pulse Width
knob above. In the LFO position, the variation of the Pulse Width around the central
50% is controlled by an additional fixed speed, internal LFO (not to be confused with
the main variable LFO on the front panel), with the amount of variation being con-
trolled by the Pulse Width knob above. Variation in the harmonic content of an oscilla-
tor (which is what changing the Pulse Width achieves) is very pleasing to the ear,
especially at lower pitches where all the associated harmonics fall within the audio
range and can clearly be heard. When selected to Env 2, the effect is best appreciat-
ed using fairly slow changes, so longer Envelope 2 Attack and Decay times are best.
14