So let’s compare the levels of individual harmonics.
Xonar D2 Out 1 (Front) Distortion Spectrum
Xonar D2 Out 2 (Rear) Distortion Spectrum
X-Fi Elite Pro Out 1 (Front) Distortion Spectrum
X-Fi Elite Pro Out 2 (Rear) Distortion Spectrum
The front output of the Xonar D2 shows a significant difference between the channels. The level of harmonics in the left channel is about 10dB lower but there is no fifth harmonic in the right channel. I don’t know the reason for that, but the rear output doesn’t behave like that. However, the rear output is worse even than the worst of the two front output channels. The line output of the Creative X-Fi Elite Pro is also worse in the level of the third and fifth harmonics, and its seventh harmonic is higher by over 10dB. As a result, the Xonar D2 wins the competition of the main outputs but Creative’s rear channels are better.
Now let’s see how the measured parameters of the two cards vary depending on the sample rate:
X-Fi Elite Pro
The Creative X-Fi doesn’t allow to record 192kHz signal, so I don’t perform the test in this mode. It’s clear anyway that this card differs from the Xonar D2. The best results in terms of noise and dynamic range are obtained at 96kHz. Moreover, the Xonar is inferior in these parameters at 44kHz, too. Is it a problem with reproduction or recording? I’ll perform another measurement using another card’s line inputs.
It’s clear that the Xonar D2’s reduction of the dynamic range at a sample rate of 44kHz has nothing to do with its ADC but comes from the reproduction section. Is it the reason for the improvement in music playback after software resampling? As I found earlier, the driver correctly transfers digital signal with 24-bit precision, so the problem roots deeper, in the DAC interface or clock generator. Hopefully, ASUS and C-Media will deal with that just as they got rid of the intermodulation distortions in the earlier version of the Xonar D2 driver.
The same test for a sample rate of 96kHz:
Comparing the noise parameters with the previous results, you can see that the ADC in the Creative X-Fi Elite Pro works best at a frequency of 96kHz whereas the same ADC in the ASUS Xonar D2 ensures the largest dynamic range at a frequency of 44.1kHz. If it were not for the annoying problem with the reproduction at this rate and if there was a smaller difference between the left and right channels of the front output, the results of the ASUS card would be even more impressive.
If you want to scrutinize the measurements results, here are the RightMark Audio Analyzer saves.