4 Asus Xonar STU
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ASUS Xonar Essence STU USB DAC Review

  1. Introduction
  2. Specifications and Product Pictures
  3. Installation and Initial Impressions
  4. Sound quality
  5. Conclusion
  6. View All

Installation is very straightforward. Just plug the bundled USB cable into a free USB port and attach the bundled power adapter into a power outlet and the DAC is recognized by the OS. You will have to install the drivers on the bundled CD or download the drivers from the ASUS website.

Now here is where the stark differences between ASUS and its nearest competitor Creative arise. The STU doesn’t come with even rudimentary software. Any Creative sound card (aside from the basic budget ones) comes with a huge bevy of software tweaks bundled along with the cards. In comparison the lack of even the Dolby software that comes with ASUS own Xonar U7 which is at a lower price point is a little surprising.

That said most people don’t use these software tweaks for a music oriented card. I would place sound quality much higher than software tweaks anyways.

The build quality and finish of the STU is good with a brushed aluminium finish of the external casing. However I wasn’t very happy with power switch. The switches are recessed into the case to prevent accidental changes but you cannot really tell if the power button is on or off. So if you plug in the DAC when the power button is left on there are sparks at the plug which isn’t very nice.

Other than that there are no complaints. The volume knob has a nice long throw and is sufficiently damped to allow for smooth changes of the volume. ASUS has also provided lots of connectivity options like Optical/SPDIF, Coaxial and USB digital input, a 3.5mm analog input, headphone and unbalanced RCA output. So like the ST/STX sound cards the STU lacks 5.1 channel support which is a downer considering the lower end ASUS Xonar U7 supports 5.1 channel output.

One special mention has to be the OPAMP tuning. ASUS provides a circuit with option to swap 3 OPAMPS. ASUS has to also be commended that their official manual on OPAMP swapping includes a detailed guide from an end user on head-fi which shows what sound one can expect by swapping the OPAMPS. That said its a bit disappointing that ASUS didn’t include any spare OPAMPs in the bundle for testing. However since the sonic characteristics of OPAMP swapping is mentioned in the manual one can purchase only those OPAMPs to get the desired sonic signature.

Other features worth mentioning are a selectable gain switch for using both high impedance and low impedance headphones/earphones, DC Servo jumpers (to minimize the pop up noise when using the built in headphone amp) and jumper settings to bypass the volume control (to use the STU as a pre amp when connected to a dedicated amplifier).

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