Sequential Prophet VS - SECTION 6 - OSCILLATORS; OVERALL SIGNAL FLOW

43
SECTION 6
OSCILLATORS
OVERALL SIGNAL FLOW
Figure 6-1 (next page) shows a general block diagram of the overall signal ow
in one voice of the Prophet VS. A "voice" is a sound producer, such as a singer
in a choir or an instrument in an ensemble. While we often speak in terms of
a single voice, it is important to remember that the Prophet VS actually has
eight voices—which is why you can play up to eight keys at once. When the
keyboard is in normal mode (not Split or Double), the basic parameters of
all eight voices are programmed identically, so that each voice produces the
same sound or eect. The dierences between the voices basically depend on
only two things: the position of the key played (which changes the pitch of the
voice), and the playing velocity (which usually aects the loudness or eective
envelope depth).
The Prophet VS's voice modules are laid out similarly to a standard volt-
age-controlled analog synthesizer, such as the Prophet-5. Technically, like all
Prophets, the Prophet VS is a hybrid synthesizer. This means that both digital
and analog techniques are employed to create the sound. As the Prophet line
has developed, functions that were originally handled by voltage-controlled
analog hardware, and which are generally drawn in analog form on block dia-
grams, have been gradually converted to computer software. For example, the
envelope generators and low-frequency oscillators (LFOs) in the Prophet-600
and -T8 were actually in software. And in the Prophet- 2000, the voltage-con-
trolled analog oscillators were replaced by a programmable sample memory.
In the Prophet VS, the most dramatic changes have occured in the oscillator
and modulation modules, which, too, are now based in digital hardware and
software.
In previous performance synthesizers, the oscillators have usually been set
up to provide only basic, raw timbre material. The means for modulating the
oscillator waveform itself has often been limited to pulse-width modulation and
swept-sync eects (such as are available through the Prophet-5's Poly-Mod
section). This has meant that the waveform from the mixer has been relatively
6
HOME

BACK