Primary Functions
Wide range analogue voltage-controlled oscillator with five waveform outputs, pulse-width modulator, and waveshapers, versatile pattern and wipe generation and animation control source

What your ear may hear as a subtle difference, your eye may see as a huge one. Since the end results in video synthesis are visual: texture, pattern, and shape instead of audio, there are a number of features and controls in this VCO design that take into consideration this unique application.

Frequency Adjustment

Coarse and fine tuning controls allow oscillator frequency adjustment across over 7 octaves, with a six-position rotary switch allowing selection of 6 separate frequency ranges. Notification LED serves as a useful frequency indicator, showing triangle wave output at lower frequency ranges.

Synchronization

Precision hard sync circuit enables jitter-free synchronization to high speed video clocks when the video is used as a stable image source. Toggle switch selects between Sync Bus 1 and Sync Bus 2, distributed from Video Sync Generator as switched sync sources — this switch may also be set to center, unsynchronized, position for free-running operation. Two separate synchronization modes, trigger and gate, can be enabled via PCB jumper. By default, trigger mode is selected — oscillator will be reset as quickly as possible after sensing a rising edge. Gate mode will hold the oscillator outputs at 0 Volts so long as sync input signal is high.

Frequency Ranges & Sync Relationships

	Min	Max	Unsynced	Field Sync	Line Sync
	1 min	4 Hz	Slow animation	Blank	Blank
	1 sec	180 Hz	Fast animation, strobing, scrolling horizontal bars	Stable horizontal bars	Blank
	10 Hz	2 KHz	Scrolling horizontal bars	Stable horizontal bars	Blank
	80 Hz	20 KHz	Scrolling horizontal bars	Stable horizontal bars	Blank
	4 KHz	700 KHz	Random textures	Little effect	Stable vertical bars
	20 KHz	3.2 MHz	Random textures	Little effect	Stable vertical bars

Frequency Modulation

Two separate frequency modulation channels are accessible, via level and inversion controls. Exponential and linear frequency modulation modes are selectable via PCB jumper and are automatically set to exponential frequency modulation. Exponential scale is 1 Volt for the entire selectable frequency range (the combined range of the coarse and fine tuning controls.)

Pulse Width Modulation

Pulse width modulation is controlled by the sum of the input to the level and inversion processor, and a bias control. Pulse width is adjustable from 0% to 100% over a 1 Volt scale. This modulation only affects the pulse output.

Sine Shape Modulation

Sine shape modulation is controlled by the sum of the input to the level and inversion processor, and a bias control. Sine shape is adjustable from 0% to 100% over a 1 Volt scale. This modulation only affects the sine output.

Waveform Outputs

Five separate waveform outputs are accessible: triangle, sawtooth, square (at half the frequency of other outputs), pulse and sine.

Specifications

Demonstration Videos

Frontpanel Key

Block Diagram

Patching Techniques

Video Clock Synchronization
A primary function of the Video Waveform Generator is its wide frequency range and ability to reset itself via its synchronization input at video clock speeds such as Field rate and Line rate in order to produce a stable, jitter-free pattern. The synchronization input is connected to the Sync Bus 1 & 2 distributed via the Video Sync Generator module to allow easy distribution of sync signals to multiple oscillators. Alternatively, the desired sync source can be patched in directly. When free-running (non-synchronized) operation is desired, the Sync Bus selection switch can be set to its middle position. When clocking Field and Line clocks, it is important to also adjust the oscillator to the desired frequency range, which must be close to or faster than the synchronizing clock. Frequency ranges 3 & 4 are optimized for Field rate clock usage, and frequency ranges 5 & 6 are optimized for Line rate usage. When locked to Field clock, the oscillator will produce stable horizontal bars. When locked to Line rate, the oscillator will produce stable vertical bars. Unsync’ed operation at frequency ranges 3 thru 6 can be used to create moving animation and texture. Unsync’ed operation at frequency ranges 1 & 2 can be used for slow animation and strobing.

Frequency Modulation
Changing the frequency of a video-synchronized oscillator will change the number of bars which are displayed. By modulating a Line synchronized oscillator with a Field-synchronized oscillator, the creation of zig-zag and curved patterns can be achieved. Complex frequency modulation relationships between multiple oscillator sources can create more intricate patterns. Additionally, feeding waveform outputs back to frequency modulation inputs will allow additional waveform creation. The square wave output, which is at half the frequency of the other outputs, can be used to alter the frequency of every 2nd waveform cycle.

Pulse Width & Sine Shape Modulation
The same basic modulation principles apply to these modulation inputs, only they serve to change the shape of the waveform rather than the frequency of the oscillator. This is especially effective when fed with external video or audio sources.

Where to purchase

Purchase this module at Analogue Haven.

If you have any additional questions about this module that you feel were not answered on this page, please e-mail us and let us know.