Introduction

ASUS is expanding its Essence line with a brand-new DAC/amp design which, like the Essence One, focuses on headphone and DAC performance. As with the recently reviewed ASUS U7, the Essence STU has a wealth of connectivity options, but only two channel analogue outs. The STU slots in between the STX and the Essence One, a very interesting DAC/amp combo.

The STU is priced at €250, which is €200 less than the Essence One, or approximately €100 above that of a normal PCI-E STX sound card. We put it through its paces to see if it is a worthy upgrade over the Xonar STX card which has for some time now held the top position in our bang-for-the-buck category.

Specifications

• Excellent audio quality as inherited from acclaimed Xonar Essence ST/STX
• Precision clock-tuning technology and asynchronous USB transfer ensure jitter-free fidelity
• Integrated 600 Ohm headphone amplifier optimizes sound detail with two gain settings
• 120 dB signal-to-noise ratio (SNR) delivers high definition audio clarity
• Dedicated jumper switch allows direct audio delivery to your power amplifier, bypassing DAC volume controls
• Three swappable Op-Amps enable tonal character tuning based on personal taste

Asynchronous USB is a nice feature, but jitter-wise, you can create something that performs just as well without it. The DAC in the STU sounds very natural and life-like, so jitter is definitely not an audible issue. The "Integrated 600 Ohm" amplifier is of course a marketing gimmick, and the integrated headphone amplifier is the same as on the STX and Zx-series sound cards from Creative. It is supplied by TI. The headphone amplifier chip is a TPA6120A2 capable of driving loads of up to 600 Ohm impedance, which does not mean anything when it comes to wattage delivered, making it a piece of useless information.

The Package

The ASUS Xonar Essence STU comes in a huge box. The unit is very well protected inside the case.


The bundle is quite extensive. You get the charger, USB cable, and stand.


The PSU is quite nice. It never runs hot and is small.