Testbed Configuration and Testing Participants
The sound cards were tested on a testbed with the following configuration:
- Mainboard: ASUS A8R-MVP (Radeon Xpress 200 chipset)
- Processor: AMD dual-core Opteron 165 at 2.7 GHz
- System memory: Corsair CMXP-3200XL 2 GB
- Graphics card: Gainward Bliss 9800GTX
- Hard disk drives: Samsung SpinPoint S250 and Hitachi Deskstar T7K250
- Optical drives: Plextor Premium and BenQ DW1640
- Power supply: OCZ StealthXstream 2 (600 W)
- Audio interface: E-MU 1820
- Headphone amplifier: C.E.C. HD53-R80
- Headphones: Grado SR 325i
I will compare the Auzen X-Fi Bravura with the Auzen X-Fi Prelude 7.1 and the ASUS Xonar D2 as well as with the Creative PCI Express X-Fi Xtreme Audio which is based on the same CA0110 audio controller as the Bravura itself.
The PCI Express Xtreme Audio makes use of Asahi Kasei DACs instead of Cirrus Logic ones you can see on other Creative cards. An eight-channel AK4359 (106 dB DR, -94 dB THD) is responsible for the card’s line outputs and a stereophonic AK4388 (104 dB DR, -90 THD) for the headphone output. The converters of the other sound cards covered in this review have better specs. For example, the Bravura’s line outputs are serviced by an eight-channel CS4382A (110 dB DR, -100 dB THD), and a stereophonic AK4396 (117 dB DR, -99 dB THD) is responsible for its headphone output.
The analog-to-digital converters of the PCI Express Xtreme Audio were chosen regardless of the tradition, too. These are two stereophonic AK5358 ADCs with rather mediocre parameters (about -100 dB DR and -93 dB THD depending on the sampling rate). For example, a WM8782 chip with the same specs is only responsible for the front-panel microphone input in the Auzen Bravura and many other Creative products. On the other hand, the WM8775 chip in the line inputs of these cards is not much better in its specs and is far inferior to the parameters of their analog outputs.
Winding up this electronics-related part of the review, I want to take a look at the operation amplifiers employed in the playback sections of the sound cards.
The Auzen Bravura has three different opamp models and you can replace them in each of the five output channels. Thus, users of this sound card are offered a unique opportunity to evaluate the effect that opamps may have on sound quality without purchasing additional chips. The default configuration is like that: an LME49720NA in the headphone amplifier, an NJM4580 for the center and subwoofer and an NJM5532 for the rest of the output channels.
Creative are more conservative in this respect and do not offer swappable opamps in their products. The PCI Express Xtreme Audio has NJM4556A opamps in the front channel of its line output as well as in the headphone output (for the front panel of the system case). It features very low distortions even at a 200-Ohm load. The rear channel is based on an NJM4558 which is not really meant for audio.
The table below summarizes the key specs of the abovementioned opamps together with those of a related model which was employed in the Creative X-Fi Elite Pro as well as in some E-MU products.
The specified distortion data for the LME49720 were gathered under special conditions, precluding us from directly comparing them to the New Japan Radio data. However, I can tell you that the LME49720 has a distortion level of less than 0.0001% in most applications. The NJM4556A is second best, ensuring the lowest level of distortions under harsher conditions than the rest of these chips. The downside of this opamp is its rather slow performance, resulting in a sudden growth of distortions at high frequencies. The NJM4580 has low distortions at low frequencies and is better high frequencies than the NJM4556, therefore I have no objections to Auzentech's installing it into the center and subwoofer channels. The use of the NJM5532 for the rest of the line outputs is questionable, though. We shall see shortly if this opamp should be replaced with something else.
Interestingly, there are four chips from New Japan Radio that are designed in an identical way but differ in their operation modes. The current balance is biased in the NJM4580 towards the input cascade. The NJM4558 can be viewed as a slowed-down NJM4556 with a weaker output cascade. The low operation current of this chip provokes such distortions that the manufacturer is ashamed of voicing the numbers. You can get a notion of them by the example of the NJM2068 which features the same circuit design and differs from the NJM4558 in slew rate and gain band product: the NJM2068 is declared to have a distortion level of 0.001% whereas the slower NJM4580 has a distortion level of 0.0005%.
Thus, we can see that the rear channels of the Creative PCI Express X-Fi Xtreme audio are inferior in quality to any components of the Auzen Bravura as well as of the rest of the sound cards I'm going to use in my tests. As for the front line output, I can’t make any predictions as yet.