OptiReg® digital power supply

As a rule, digital circuits require extensive regulation to reduce digital noise and phase noise, which if left unresolved, pollute the audio signal. They are also needed to meet the tight supply voltage tolerances required for optimum operation of digital circuits.

Most digital power supply sections in compact disk sources employ basic regulation stages that consist of one single chip regulator (even if many "one stage" regulators are used simultaneously). The resultant effective operating frequency range is only up to ~1kHz , thereafter losing regulation quickly above.

Bearing in mind that digital noise exists all the way into the GHz region and that audio signals reach up to 20 kHz but are influenced by ultrasonic noise of much higher frequencies, the result is a large amount of noise has not actually been suppressed. Still in abundance, digital noise is therefore still very much in existence, continuing to pollute the audio signal.

Understanding and appreciating that digital noise has a very wide frequency bandwidth range is critical. In the CD-77, rather than mindlessly repeating the same generic regulator chip in all positions, a total of 14 different but specifically designed regulators are employed.

Block Diagram illustrating AMR's OptiReg circuitry in the CD-77 CD-Player

Each regulator is matched to the subsequent operational section by applying the most appropriate type of regulation circuit (series regulation, shunt regulation, optimised for lowest noise, optimised for lowest impedance etc.) The result is that every power supply section is fully optimised for every digital circuit to ensure the best possible performance.

The end product was certainly worthwhile, as supply noise has been reduced by a factor of more than 1000 times compared to standard regulators to result in the virtual elimination of digital noise.



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