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Distortion and Noise Floor Measurements of Macintosh Built-In and Third Party Audio

A list of measurements performed by Mac the Scope is given below. The computer's sound output jack was connected to the sound input jack with an audio cable. Waavebox provided the signal. (The one-click measurement procedure also is included with the Mac the Scope demo / updater package.) A "perfect" response would show a single peak at 1 kHz. Most measurements were made with the computer also supplying the test signal (full duplex), except where noted. Thus, the measurement includes noise and distortion both from the computer sound output and the sound input. Measurements with Mac the Scope the results are summarized in the table. Differences of a few dB are insignificant. The devices in the table are ordered chronologically. Measurements are full duplex, unless noted. Values in dB relative to digital full scale; e.g., -120 dB = 0.0001 %. Device Apple MacBook (Late 2006) Built-In Audio (24 bit 2 channel / 44.1 / 96 kHz) M-Box USB Audio Interface (24 bit 2 channel / 44.1 / 48 kHz) (CoreAudio) Apple 867 MHz G4 DP Mirror Drive Door (CoreAudio) LynxTWO (PCI card, 24 bit 6 in / 2 out / 8 kHz to 200 kHz sample rates)* (CoreAudio) RME ADI 8 Pro DS with Digiface (PCMCIA or PCI card, 24 bit 8 in / 8 out / 44.1 / 48 / 88.2 / 96 kHz)* (ASIO) LynxONE (PCI card, 24 bit / 44.1 / 48 / 50 kHz)* (ASIO) Griffin iMic (USB, 20 bit / 44.1 / 48 kHz)* (Sound Manager and CoreAudio) Apple PowerBook G3 500 MHz Apple 333 MHz iMac G3 (OS 8.6, virtual memory) Apple 233 MHz Power Macintosh G3 "Beige" desktop model (OS 8.1, virtual memory) Apple 117 MHz PowerBook 5300ce (OS 7.6.1, Appearance 1.0.1, virtual memory) Apple 80 MHz Power Macintosh 7100/80AV (OS 7.5.1) Apple 80 MHz Power Macintosh 7100/80AV (same, but signal from PowerBook 5300ce) *The LynxONE and LynxTWO are PCI cards (this dispels the longstanding myth that having the sound card "inside" the computer causes excessive noise). The RME ADI-8 is an external, rackmount ADC / DAC that requires an additional interface (PCI or PCMCIA) for connecting the sound input to the computer.

Similar measurements of sound cards designed for Wintel PCs can be found at these websites: http://www.pcavtech.com/soundcards/reports/ http://www.rockpark.com/soundcards/ http://www.hut.fi/Misc/Electronics/docs/soundcardtest/

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