PCB Design and Technical Specifications
The specs and features of the Auzen X-Fi Bravura 7.1 are detailed at the manufacturer’s website and I don’t want to simply copy and paste that information. I will just dwell on a few of the most important things.
The Bravura is extremely close to Auzentech’s X-Fi Forte and HomeTheater products in its functions, components and exclusive technologies. It too has a symmetric power circuit, two microphone amplifiers with independent converters, and an individual headphone output. The similarity with the Forte is emphasized by the AK4396 DAC in the headphone amplifier, but the rest of the circuitry is different. In the Forte, the headphone output duplicated the line output of the front channel, making the individual converter unnecessary, so it was removed in the HomeTheater. Now it returns with an important mission. It allows the headphone amplifier to work independently of the line output.
The amplifier itself has changed, too. It used to be driven by the front output’s low-pass filter but now the headphone amplifier is itself part of the filter. ASUS implemented this solution in its Xonar Essence STX, by the way. Otherwise, it is the same dual-channel amplifier circuit with a buffer of eight transistors. As if in response to my thoughts about the weak power supply of this circuit on the Auzen X-Fi HomeTheater, the engineers installed four polymer capacitors instead of two aluminum ones into the power converter and added three thick printed conductors into the amplifier itself, obviously to better cool the transistors. We’ll see the effect of this shortly.
As opposed to the previous Auzentech products and to the card’s own line outputs, the Bravura’s headphone amplifier filter employs higher-quality capacitors. It is the metallized propylene FKP2 manufactured by WIMA. The opamp in the headphone output is swappable without soldering, which is handy. By the way, there are four empty places for transistors in the headphone amplifier and a place for one more opamp on the reverse side of the PCB. It seems that the engineers had wanted to separate the headphone amplifier from the DAC filter at first.
The headphone output is designed for users who prefer 6.3mm rather than 3.5mm connectors. Besides professional audio equipment, 6.3mm headphones could only be directly connected to the ASUS Xonar Essence. Owners of other sound cards had to use an awkward adapter or an external amplifier.
Judging by the opamp compatibility table, the design of the line output filters has changed somewhat since Auzentech’s earlier products. Although the Bravura is not declared to deliver optimum sound quality with the decompensated opamps of the OPA637 series, I didn’t have any problems with them in my tests. So, you can use such opamps with your Bravura if their price suits you.
The inputs have remained the same as in the previous Auzentech products except for the different way of switching the operation mode of the microphone amplifier. Instead of a switch, there is now an electronic selector. You can refer to the How To section of the product page for details. This unit is also responsible for the operation mode of the headphone output DAC and allows to enable a smooth frequency response decay or lower the peak output signal level. The headphone and line outputs are controlled in sync but by different rules.
It is unclear why the Auzentech engineers preferred to implement this array of hard-to-access micro-switches and barely visible LEDs. Software-based control over these features would be far more practical.