FXpansion DCAM Synth Squad Operation Manual - Manual (Page 31)

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4:4 Audio-rate sample and hold
Cypher features the ability to sample and hold (S+H) an oscillator using the frequency of another, at audio-rate. A sample
and hold operation involves the amplitude of one signal being sampled and held at a regular clock pulse. On each clock
pulse, the signal’s amplitude value is snapshotted (‘sampled’) and kept constant (‘held’) at the same value until the next
clock pulse.
The sample and hold technique is used for a variety of purposes in analogue synthesis, such as generating a random
LFO by performing S+H on a noise signal.
In Cypher, it is used to provide another audio-rate modulation technique to offer increased timbral variation from each osc.
The clock pulse is provided by the modulating oscillator’s frequency. The result is a quantizing effect on the modulated
osc’s waveshape, illustrated by the following diagram:
0.5 1.0 1.5 2.0
Time mS
0.4
0.2
0.2
0.4
Voltage V
Audio-rate sample and hold on a Triangle waveform.
The sonic characteristics are gritty and buzzy, reminiscent of low-resolution FM and sampling.
The S+H is achieved by using the
Blend control on each Osc, labelled ‘S+H-Osc-Noise’. This control allows a blend of the
S&H signal and the actual oscillator signal.
The S+H position of the Blend control is not comparable to the
FM from  and WM from  amount controls elsewhere
in Osc2, Osc3 and the filter section. The S+H process is always active, with the Blend control allowing you to alter the
oscillator mix to include the S&H signal.
Here is a summary of what is heard when each osc’s Blend control is turned fully to the left:
Osc1 Osc2 sampled & held by Osc1’s frequency.
Osc1 is the clock trigger acting on Osc2
Osc2 Osc3 sampled & held by Osc2’s frequency.
Osc2 is the clock trigger acting on Osc3
Osc3 Osc1 sampled & held by Osc3’s frequency.
Osc3 is the clock trigger acting on Osc1
Using audio-rate sample & hold
. At first you won’t hear anything as the pitch of both oscs is the
same.
Turn up the Osc1 Scale control while playing a key.
1. Fully turn down the S+H-Osc-Noise (Blend) control on Osc1.
The sound of Osc2, sampled and held by Osc1’s frequency, is
now the output of the Osc1 block.
You’ll now hear the sound of Osc1’s frequency applying a sample & hold process to Osc2. Lower Osc1 frequencies result
in a more quantized Osc2 signal. Many parameters can influence the sound. Try the following to investigate the affect of
these parameters on the timbre (you can adjust the parameters manually or by applying modulation to the controls):
• Change the waveforms of both oscs using the
Wave control
• The pitch ( Scale) of Osc2
• Increase Osc3’s Scale and then increase Osc2’s FM from  control