Specifications and benchmarksThe tests were conducted using the following equipment:
Please also see the "Specifications" section of the γ1 website for related information.
Note: γ2 will not decode AC3, ADAT or other non-PCM, non-audio data streams.
RMAA test resultsSeveral tests were performed, one with the M-Audio Firewire Audiophile mobile interface running in loopback mode to establish the baseline (lowest limit of measurement resolution). The Firewire Audiophile's S/PDIF output was then connected to the companion γ1 coaxial input. γ2's analog output is fed back to the M-Audio Firewire Audiophile analog input for recording in the remaining tests (for the three digital filter settings).
RMAA loopback testing sets the measurement sound card's ADC sampling mode the same as the digital output. With the γ2, this artificially makes the test results worse for any mode less than 24-bit 96KHz. This is the mode which γ2's DAC operates at regardless of the input stream mode, due to the upsampling. Hence, only the 24-bit 96KHz results are shown here. The "32 bits" results are actually in 24-bit mode but contained in 32-bit words.
Click on the following links to see the results.
Comments on the RMAA test resultsγ2's measured frequency response is flat with extended bandwidth and minimal passband ripple (see graph below). The noise floor, THD and IMD distortion products, and stereo crosstalk are all supremely low. In fact, the results are limited by the M-Audio Firewire Audiophile's loopback baseline. Some measurements were actually better than the baseline due to γ2's superior DAC. Indeed, the γ2's performance exceeds that of the measurement instrument, thus the results are arrtificially limited by it. Nevertheless, the numbers compare favorably to other far more expensive high-end DACs.
It is also noteworthy that (in separate tests), changing the ASRC chip to the SRC4192, or changing the DAC chip to WM8742, or changing the opamp to OPA2365 did not produce tangible differences in the RMAA test results.
Oscilloscope waveformsSome oscillogram waveforms of the γ2 DAC are shown below. All input waveforms are digitally generated on the computer. A Tektronix TDS2014B digital storage oscilloscope is used to display the analog line output waveform.
The impulse and square wave response graphs exhibit the Gibbs Phenomenon ringing behavior. It is affected by the choice of digital filter setting, as shown. Please see a discussion about the digital filters in the Tech highlights section.
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