Advancements in computer and component technology have created a genesis in professional audio equipment, allowing studio mixing consoles to offer increased functionality in similar or smaller overall footprints as digital studio mixing consoles emerge. A collection of faders, knobs and buttons provides a control surface for mixing audio, including routing, creating effects, manipulating, and combining multiple digital and analog audio input sources. The experience is enhanced with rotary optical encoders, providing a means of customizing controls, adjusting various audio characteristics and interfacing with on-screen menus.
These devices provide exceptional resolution and flexibility compared to potentiometers in analog consoles. Rather than measuring exact characteristics, rotary optical encoders convert user input, when an adjustment is made to the encoder position, to square wave digital pulses with resolution up to 256 pulses per revolution. Output voltages are compatible with HCMOS, CMOS and TTL systems for processing. Magnitude and direction of adjustment are provided in two-bit incremental quadrature signals. Long rotational life, reliability and small package size, essential to studio audio mixers, are just a few of the benefits rotary optical encoders deliver.
How Rotary Optical Encoders Work
Optical encoders utilize a light source, code disk and detector to generate the digital signal. Light passing through slots in the code disk is detected by a custom ASIC with a switching rate as low as 200 ns and translated into a digital output pulse essentially free of noise and distortion. Since an optical encoder does not have a mechanical contact wiper, its useful life may increase to 200 million rotational cycles at up to 3,000 revolutions per minute (rpm) with the addition of ball bearings in next-generation encoders. Compact packages and splash-proof shaft seals are available on some encoders for space and moisture concerns.
Typical Interface Circuits in Studio Mixer Consoles
Rotary optical encoders are ideal for pan, auxiliary and custom controls in studio mixer consoles. Jog shuttle control, possible with these encoders, allows scrolling of menu options and searching for specific points within audio files for editing. An optional momentary push switch can be utilized for menu selection or power functions. These functions allow digital mixing consoles to incorporate greater functionality with no footprint increase.
Studio mixing consoles using rotary optical encoders benefit from a significant reduction in memory overhead, wiring and program speed. When contacting encoders are used, the turn life cycle and rpm capabilities decrease as mechanical wear and required circuitry increase. Resolution and rotational life are superior with optical solutions, and they provide the durability, flexibility and functionality audio professionals desire. Solid-state electronics produce the output signal, and neither electrical noise nor mechanical wear interferes with an extended product life.
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