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Pack 6/7 Oscillator Technical Information
CK_Oscillators are designed to operate with system sample rates 44.1Khz and over
They are designed for minimal CPU usage and so do not use Oversampling
Most CK_Oscillators use a wavetable system that controls 256 harmonics
This covers a wide frequency range with full spectrum harmonics (44.1Khz system)
Because there are 256 harmonics it does affect the sharpness of 'single wave' Low frequency sounds
The significance of this is 'arguable' but i am providing this information for the 'techies'
When used with the standard 44.1Khz system:-
Notes/Tones down to 86hz have harmonics extending up to 22 Khz (i.e Full spectrum at 44.1Khz)
From 86hz to 43hz the harmonics gradually roll off down to 11 Khz
From 43hz to 20hz the harmonics gradually roll off down to 5 Khz
So even bass tones at 20hz still have harmonics extending up to 5 Khz
You can easily create Bass tones with harmonics extending to 22Khz simply by using a 'Dual' Oscillator mode
or a Multi_Oscillator and shifting the pitch of the second wave higher
This also allows a more complex harmonic mix to be created compared to the rigidity of a single 'fixed wave'
because you can use different waveforms to define the 'Bass' and 'Mid/High' end harmonics and even modulate/mix between them
Alternatively, you can use Phase Dist/Mod, RingMod, Shaping etc Modes(Flexi Osc) to create extended 'Synthetic Harmonics' (*See: Harmonics section below)
Listen to this sample of a single saw wave to hear how the harmonics respond:- Flexi_Osc Saw Sweep 5Khz to 27Hz
Most Oscillators have a separate '2k' version:-
This indicates that the Wavetables are 2048 samples, 4x larger than used in the standard oscillators
The '2k' versions will give improved sound quality but will use more CPU and memory resources
On my PC system the CPU increase is significant, although some people have reported only a small difference
This is the same single saw wave as above but using the Flexi_Osc_2k version:- 2k_Flexi_Osc Saw Sweep 5Khz to 27Hz
Most people probably wont be able to 'hear' any difference between them - but the '2k' output has lower 'interpolation noise'
The following Spectrum images show how 'interpolation noise' affects the signals:-
From the above, it can be seen that the '2k' versions have an improved 'smoother' response
Controls common to Pack6 and Pack7 Oscillators:-
*Note: Not all controls appear on all modules
Pitch: The pitch/frequency the oscillator produces
This is the main input to use for pitch modulation
Pitch Ref: The Harmonic Reference pitch for the 'Freq Limit System: B' *See below*
This input has no effect on the oscillator pitch and should Not be modulated
Pitch Mode: The pitch/frequency system can be either Octave, Khz or Hz
The standard pitching system in SynthEdit is Octave, but this system uses the highest CPU when modulated in realtime
Khz, Hz systems use much less CPU when modulated in realtime
PitchMod Accuracy: (High, Low)
High: Realtime (sample-by-sample) modulation. Uses most CPU but gives the best sound quality
Low: Block-Rate modulation. This is OK for most LFO/Envelope/Pitch Bending modulation and uses much less CPU
Analogue Drift Depth: This internal feature requires minimal CPU 0.010%
Analogue Drift Rate:
Controls the Depth and Rate of Analogue Drift. 0v = Digital (Off)
Simulates the small voltage variances of analogue synths causing pitch drifting over time
Can also be used for 'irregular Chorusing/Detuning' with multiple Osc's which can sound more 'natural' than Lfo/Delay based chorusing
And with the added benefit of using virtually No CPU !
If you need to 'Lock' several oscillators to the same 'drifting' pattern use an external 'Analogue Drift' module linked to each of them
Tuning (ratio): Used in Oscillators with multiple voices
The Pitch input defines the 'Root' or 'Reference' frequency
Each voice can be 'Tuned' relative to the Pitch
Eg: to play at the Pitch frequency. Tuning = 1.0
to play at one Octave above the Pitch. Tuning = 2.0
to play at one Octave below the Pitch. Tuning = 0.5
If you modulate the 'Pitch' signal, all voices will modulate relating to their 'Tunings'
For independent modulation of 'Tuning' inputs you can convert Pitch(Octave) signals using a '2^x' module (Pack 4)
The '8x_Osc_Tuning' module provides a convienient way of setting fixed Tunings by semitones (+/-48)
Eg: It would be easy to create a 'Chord' sound from one oscillator
Phase: Sets the oscillator starting Phase
This can be modulated for 'Phase modulation' or 'FM' effects
Sync: Resets the phase of the oscillator
Can be used for 'Note-On sync' or for 'Sync modulation' by another wave/oscillator
This is a 'Hard Sync' system which will cause 'Synthetic harmonics' (aliasing)
Sync Accuracy:
High: Intra-sample accuracy - for use with 'Sync Modulation' (recommended)
Low: Sample accurate sync, for Note_On Sync. Can cause increased noise with 'Sync Modulation'
Waveform: Set the waveform shape from the following:-
Sine, Saw, Ramp, Soft Ramp, Peak Ramp, Square, Triangle, Peak, Octava, Cluster1, Cluster2
Wave Quality:
High: Wavetables are interpolated creating a Much smoother sound (recommended)
Low: No interpolation, creates a 'bite' or 'metallic' sound but is not really suited for pitch modulation (IMO)
Uses less CPU in most cases
Harmonics: (1-256) Allows you to set the Maximum number of harmonics in the waveform
Can be used as a simple Low pass filter by removing the higher harmonics at no CPU cost
CK_Oscillators can only control the Harmonics in the internal Wavetables
'Synthetic Harmonics' that are created by Phase Modulation/Distortion, Waveshaping, Sync, Ring etc cannot be directly controlled by the CK_Osc's
'Synthetic Harmonics' are related to the number of harmonics in the Wavetables and CK_Osc's allow you
to set the number of Harmonics used so you have some control over the 'Synthetics'
EG: Phase Dist/Mod is a mode that creates a lot of 'Synthetic harmonics'
To control this simply restrict the harmonics in the Waveforms
Freq Limit(Hz): Restricts the Harmonics in the *Wavetables* below this Frequency
This acts like 'Band limiting' or Low Pass filtering at no CPU cost
Freq Limit System:
OFF: Harmonics can extend beyond Nyquist(1/2 sample rate) creating fold back frequencies
Can be used for wierd fx etc
A: Harmonics are *removed* above the 'Freq Limit'
When modulating the Pitch, if the 'Freq Limit' is low and/or the playing Note is very high (eg A7+)
then noise may be heard as the harmonics are removed or replaced
B: Harmonics are determined by the 'Pitch Ref' input
Now when modulating the Pitch, Harmonics are allowed to extend beyond the 'Freq Limit'
This allows a much better modulating sound with high Notes and/or low 'Freq Limit'
As a general rule System A should be used if 'Freq Limit' is set near to 'Nyquist' (1/2 sampling rate)
System B should be used if 'Freq Limit' is set well into the audible band
HOLD: (On,Off)
Freezes the output when 'ON' and resumes when 'OFF'
Active: (On,Off)
If the oscillator is not being used set to 'OFF' which uses no CPU