Specifications

The Power Mac G5 computer also has the ability to lock its internal audio hardware to the incoming audio

stream to synchronize the audio subsystem to an external device supplying the audio stream. This function

allows audio and video to play in sync with the external audio or video device. The data format for signals

transmitted over the optical cable is S/PDIF protocol IEC 60958-3.

The Power Mac G5 computer’s audio subsystem has built-in sample-rate conversion (SRC) that allows the

incoming audio to have a different rate than the playback audio, enabling the audio to come in the digital-in

connector. For the best digital input quality in its purest form, set the audio clocking preference to “External

Clock.”

External Clocking

When the Power Mac G5 computer is set to “External” clocking, the computer audio circuitry will track and

follow the incoming digital sampling rate and lock the internal audio hardware to the sampling rate of the

external device. The external clock must be stable enough to be locked onto, otherwise the digital circuit will

signal an error and the driver will fall back to using the internal clock.

Internal Clocking

When the Power Mac G5 computer is set for “Internal” clocking, the computer audio circuitry will run using

the computer’s internal clock. Incoming digital audio is automatically sample-rate converted to the selected

output sample rate using the sample rate converter in the audio chip. The sample rate converter is high quality

and does not use CPU bandwidth for audio conversion.

Optical Digital Input/Output Specifications

Based on playback of a 1 kHz, -1dBFS 24-bit sine wave playback, 24-bit 44.1 kHz output sample rate (unless

otherwise specified below) the digital sound input and output have the following electrical characteristics

(nominal specifications):

●

Fsi – input sample rates (external clock mode): 32 kHz, 44.1 kHz or 48 kHz

●

Fsi – input sample rate (internal clock mode): 16 kHz – 96 kHz

●

bits per sample: 16-bit or 24-bit

●

SNR (external clock mode): >130 dB

●

SNR (internal clock mode, 16 kHz < Fsi < 96 kHz): >110 dB

●

THD+N (external clock mode): < -130 dB (0.00003%)

●

THD+N (internal clock mode, 16 kHz < Fsi < 96 kHz): < -110 dB (0.0003%)

Input and Output Devices

Audio