2-OP FM Mode
2-OP is an abbreviation for Yamaha’s ‘2-operator’ FM synthesis. The E330 generates 2 sine oscillators
and FM modulates one with the other. The modulated result is on
OUT 1
, while
OUT 2
has just the sine
VCO which is modulating the carrier (the audio). The 2 parameters you can control are the Depth of
Modulation (or the ‘Index’) using
MODULATION A/MOD A
and the ‘Ratio’, which is the ratio of the
frequency of the modulator to the carrier, using
MODUALTION B/MOD B
.
The Index can vary from 0% (
OUT 1
is just a pure sine wave) to over 400% (harmonic sidebands).
The Ratio is a 64-level, quantized look-up table as in the original Yamaha chips, from 0:0 (which means
OUT 2
is muted) to 7.875:1 (
OUT 2
is 7.875 times the frequency of
OUT 1
). The steps are in ratios of
0.125. This allows
OUT 2
to ‘track’
OUT 1
as either a sub-harmonic of 1/8
th
of
OUT 1
(a RATIO of
0.125:1) all the way past the 7
th
harmonic (RATIO of 7.00:1).
OUT 2
can be used in many ways. Common patches are using an external mixer to ‘add back in’ the
harmonics, or using a VCA to modulate
OUT 2
, then patching it back into the E330’s
FM
input. This can
create a wild assortment of audio from
OUT 1
, from gongs and cymbals to white noise bursts. Another
common patch is to apply an envelope to
MOD A
CV in, which will produce drum sounds.
It is important to note that the internal audio sample rate of the E330 is 41KHz, so if the main audio
out (
OUT 1
) has high INDEX and/or high RATIO, the sine output on
OUT 2
can be aliased which will
result in ‘odd and strange’ waveforms. This may be useful in some situations.
MORPH Mode
MORPH
mode generates 2 identical frequencies, but independent waveforms on
OUT 1
and
OUT 2
.
The 32 wavetables used are from the E350 Morphing Terrarium and are listed at the website link at the
top of Page 1.
MODULATION A/MOD A
selects the wavetable for
OUT 1
, and
MODULATION B/MOD
B
selects the wavetable for
OUT 2
.
CLOUD Mode
Cloud mode is a 4-oscillator Sine and Saw VCO with variable detuning, called ‘Spread’. This is
equivalent to a subset of the E340 Cloud Generator, without the independent ‘CHAOS BANDWIDTH”
control.
OUT 1
has the Sine VCO and
OUT 2
has the Sawtooth VCO. With the 2 MOD controls at ‘0’ and no CV
inputs, the VCOs are a single pitch (‘unison’ tuned). As
MODULATION A/MOD A
is increased, the 4
frequencies spread apart (‘detune’) to cause beating, which richens the sound. The range of ‘Spread’ is
from very small to very wide.
The second control,
MODUALTION B/MOD B
, also detunes the 4 VCOs but does so using filtered
noise (similar to the ‘CHAOS’ in an E340). At small settings, this adds a ‘shimmer’ effect to the overall
detuned sound. As the depth is increased, the outputs evolve into a mass of buzzing clusters of audio
(the ‘angry bees’ setting). In general, just a small amount of effect is needed to get the deep ‘detuned
lead sound’. Setting Spread to ‘0’ and Chaos to ‘10’ will generate noise out of both outputs.
General Info
CV Inputs: -5V to +5V, DC to 8KHz.
Audio Output: 9V pk-pk (typical 10V pk-pk max), 41KHz sample rate, 16bits.
Frequency Range (OUT 1): 16Hz to 18KHz (OUT 2) 2Hz to ~21KHz.
Power supply range: +-9V to +-15V
Power supply current (typical): -12V @10ma +12V @ 48ma
1V/OCT trimmer:
There is a trimmer to adjust the VCO scaling to 1V/OCT as needed.
