This is an updated version of the low frequency oscillator on the classic analogue synthesiser, the Korg MS-20. It features two output waveforms, triangle and square. But, the design also incorporates a ‘Shape’ control that affects the rise and fall times of the triangle waveform. Therefore, you can get sawtooth and reverse sawtooth from the triangle output by using the Shape control.
The Little LFO uses an integrated dual SPDT FET switch to enhance the Korg design. It also allows the use of waveform synchronisation. This is where the output waveform is reset back to zero when a SYNC pulse arrives from another module. A range switch may be fitted to allow even lower frequencies to be made.
(Note: The Little EG is no longer available from Oakley. The following text is from the original Little EG manual written by Tony Allgood.)
This is a simple but effective envelope generator module primarily designed for use in modular synthesisers.The envelope generator or EG for short, generates a rising and falling voltage at its output when triggered by a gate signal. The speed of the rise in output voltage is determined by the Attack control. The speed of the fall of the output voltage is determined by the Decay or Release controls. The output of an EG is traditionally patched to the VCA control voltage input, to control the volume of the note when the keyboard is pressed; or to the VCF, where it dynamically alters the harmonic structure of the sound throughout the duration of the note played. There are three basic analogue EG types available: attack-decay (AD), attack-release (AR), and attack-decay-sustain-release (ADSR). The AD type produces a rising voltage in the attack phase. This rises exponentially from zero until a predetermined value is reached. The decay phase then starts where the output voltage falls back to zero. If the gate is removed during the attack phase, the decay is prematurely started and the voltage output will fall without the peak ever being attained. Two pots are required for the control of an AD type EG. The AR type produces a rising voltage in the attack phase, again rising exponentially, to the sustain level. The voltage will then remain at this level for as long as the gate is held high. When the gate is removed, the output will fall back to zero. This is the final release stage. Again, only two pots are needed for an AR-EG.
The Oakley Little EG is able to produce AD and AR simultaneously. The unit can be wired up to have two pots, so that attack and decay/release phases are controlled together for the both types of EG output.
- Added range switch for LFO.
- Omitted LFO pulse output to save panel space.
- Used a toggle switch to select between AD/AR envelope shapes to save panel space.
- Front-Panel-Express Panel.
Note the unusual location for LEDs and toggle switches to the lower right of the pots. This works for Oakley modules because of their orientation on the back of the panel.