Yamaha PLG150AN Manuel du propriétaire télécharger pdf (Page 8)

Analog Physical Modeling Synthesis and the PLG150-AN Tone Generator

However, the instrument also gives you a wide variety of tools (including Pulse Width Modulation

and Edge) for introducing analog-like “imperfections” to the waveforms and making them much more

complex and interesting.

The VCO of the PLG150-AN actually has two blocks: VCO 1 and VCO 2. With VCO 1, you can

select a variety of waves, and it can be conﬁgured with one of three “sync modes” that syncs “master”

and “slave” oscillators within the VCO 1. Thus, when the sync is on, the VCO 1 is actually two oscil-

lators in one, and additional waves are available.

The VCO 1 is always ﬁxed as the FM carrier, but the carrier can either be the master or slave oscillator

depending on the selected algorithm, when Sync mode is set to on. The FM modulator can be

selected from VCO2, the PEG, FEG, LFO1, LFO2 or others. The Pitch Envelope Generator (PEG)

lets you determine how the pitch of the VCO changes over time, and the LFO can be used to modulate

the VCO to create vibrato.

The PLG150-AN also has a second oscillator section: VCO 2. VCO 2 has many of the same waves

and controls as does VCO 1, but differs slightly in the waves that are available . For certain waves, it

also features special cross-modulation that generates complex harmonics by modulating the fre-

quency of the oscillator. The VCO 2 can also be set (with the Sync parameter) to modulate the VCO

■

Pulse Width and Pulse Width Modulation

In conventional analog synthesizers, pulse width (PW) is used to change the shape of a pulse wave-

form. This changes the harmonics or overtones (which determine the timbre or tone) of the sound.

Pulse width modulation (PWM) uses an LFO to periodically change the width, and hence, the har-

monics.

The PLG150-AN lets you control not only the Pulse wave in this way, but also Saw and Mix (a com-

bination of Saw and Pulse). In addition to using an LFO to modulate the Pulse Width, the PLG150-

AN lets you create a “fat” chorus-like effect, depending on the parameter settings.

Basic sawtooth

waveform.

When Pulse Width

is set to a value

under “64”.

...the sound has

many harmonics.

...the sound is that

of typical pulse

wave, with only

odd-numbered

harmonics.

...the sound has

many harmonics.

When Pulse

Width is small...

When the Pulse

Width is set to

"64" (50%)...

When Pulse

Width is large...

Saw (Sawtooth)Pulse

1 2 3 4 5 6 7 8 9 10 11 12 13 ... 76 77

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Yamaha PLG150AN Manuel du propriétaire Page 8

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