The 921B generate frequencies from 1Hz to 40kHZ minimum. Like 921 oscillator, this is one of the building block of analog synthesis. This oscillator generates both sub-audio and audio frequencies for control an audio signal use. 

The frequency pot at the top of the module has a two octave range for fine tuning. The range switch shifts the frequency of the range switch correspond to traditional organ pipe range notations. Fixed level outputs for sine, triangle, sawtooth, and rectangular waveforms are found at the right of the module. DC modulate is a linear frequency control input (does not conform to 1V/octave). AC Modulate input is a capacitor coupled circuit like the DC Modulate input, however, blocking constant DC voltages. 

921B oscillators are generally ordered in sets wired to a common 921A oscillator driver. The 921B is controlled by the oscillator driver for both exponential frequency control and rectangular width voltage control. For ease of tuning, and convenience, the 921B are connected to a single 921A may all be moved in parallel by the manual controls found on the 921A. 

921B may be phase locked together via the Synch. Input jack. Phase locking capability is generally limited to the first six harmonics of the input signal. A sawtooth waveform is recommended for best synchronization results. 

Toggle switch allows to deactivate the frequency control of the associated 921A oscillator driver. 



The 921B oscillator set forms the core of the modular synthesizer for generating both audio frequencies and sub-audio frequencies. The outputs of these oscillators can be used alternately or concurrently, for a primary signal (tone generation) or as a control voltage source. 

As an audio generator, the 921B production of sine, triangle, sawtooth waveform with all numerical harmonics. 1V/octave frequency control through the 921A oscillator driver constitutes the primary way in wich controllers are connected to the oscillators. However, independant linear control voltage inputs are found on each 921B for additional control. Varying control voltages for vibrato, frequency modulation at audio rates, and many others control voltages of this type may all be introduced directly into the 921B oscillator through the D.C. Modulate input jack. The A.C. Modulate input functions in much the same way, however, blocking D.C. voltages (like a keyboard input), and permitting only constantly varying sources to modulate the oscillator frequency. 


As low frequency control voltage generators, or audio frequency control voltages, the 921AB oscillator sets can be modulate any voltage controlled source. Variations of frequency, timbre, amplification, or speed of function (speed of the clock on a sequencer) are all accomplished with these modules. 


Frequency range : 1Hz to 40kHz
Frequency control inputs : DC Modulate / AC Modulate
Manual control inputs :
Range switch : changes VCO frequency in steps of 2:1 (octave steps)
Frequency knob : adjust frequency +/-12 semitones
Waveforms Output : 4 : sine, triangle, sawtooth, rectangular
Nominal level : -4dBm (approx. 1,3Vpp)
Nominal output impedance of sine, triangle, sawtooth : 1KΩ
nominal output of rectangular : 2,5kΩ
All waveforms are centered around zero volts.

Power supply requirements : +12V@40 mA / -12V@40mA