FXPANSION DCAM SYNTH SQUAD, Руководство по эксплуатации

Страница: 32 / 110

4:5 Variable-depth oscillator sync
Compared to FM, oscillator synchronization is far more common on classic analogue synthesizers. This is because it
makes complex harmonic timbres possible without suffering from the inherent tuning drawbacks of analogue frequency
modulation.
Most conventional implementations of osc sync are known as ‘hard sync’. This is when the cycle of an oscillator (called the
‘sync source’ or ‘sync master’) is used to reset the phase of a second oscillator (the ‘sync slave’).
In order to create a useful effect, the sync slave osc’s frequency should be set higher than that of the sync source osc.
The end result is a more complex waveform from the slave osc that contains additional harmonics, but maintains the
same fundamental frequency as that of the master osc.
Main uses of osc sync
A practical advantage of osc sync is that it allows you to combine oscillators without the inherent beating that occurs
by mixing them normally (due to the fact that it is virtually impossible to get two analogue oscs perfectly in tune with
each other). While the sound of oscs beating against each other is often desirable, there are situations when it can be a
problem.
Perhaps the most well-known uses of osc sync is to create extreme, aggressive lead sounds. Another common technique
is to perform ‘sync sweeps’ – where the slave osc’s frequency is swept manually or with an LFO to create harmonically
rich movement.
Variable-depth osc sync in Cypher
In Cypher, Osc1 is the sync master, and Osc2 and Osc3 are the sync slaves. Both Osc2 and Osc3 can be synced to
Osc1’s frequency – their phase can be reset on each cycle of Osc1.
You will notice that rather than simply having ‘sync on/off’ buttons for the slave oscs, Cypher has variable controls, called
Sync to 1 , for these two oscs.
Minimum (0) and maximum (1) settings
When Sync to 1 is turned up to its maximum setting (1) on Osc2 or Osc3, the phase of these oscs is reset fully to
their initial state upon each cycle of Osc1. This technique is commonly known as ‘hard sync’. When the control is at the
minimum setting (0), no osc sync occurs.
Settings between 0 and 1
At Sync to 1 settings between 0 and 1, Osc2 or Osc3 reset their phase on each Osc1 cycle only if the following condition
is met:
Osc2 [or Osc3] phase > (1-
(Osc2 [or Osc3] Sync to 1 amount)
100
)
This resembles some analogue implementations of ‘soft sync’, and can create a range of complex sounds that are not
possible with full, ‘hard’ osc-sync.
This example shows a saw-up waveform (filled) on
Osc2, synced to a lower-frequency saw-up waveform on
Osc1. The Sync to 1 control is set to 100%.
Note the phase of the Osc2 waveform is reset to 0 on
every completed cycle of Osc1.
In this example, the Osc2 waveform does not re-sync on
the first cycle of Osc1, because Osc2’s phase is approx.
0.35, which is not greater than 0.5 (or 1-( 50 /
100
)).
On the second cycle of Osc1, Osc2’s phase is approx.
0.67, which is greater than 0.5 – therefore Osc2’s phase
is reset to 0 and it syncs to Osc1.
0.5 1.0 1.5 2.0
Time mS
0.2
0.4
0.6
0.8
1.0
Phase
0.5 1.0 1.5 2.0
Time mS
0.2
0.4
0.6
0.8
1.0
Phase
Sync to 1 at 100%
Sync to 1 at 50%