Great sound at a cost you can afford

You can enjoy high quality music from a sleek and compact digital-to-analog converter (DAC) from Asus, Xonar Essence STU USB.

The STU is both a DAC and headphone amplifier and comes in a slim profile. And you can further save desktop space by placing it vertically with a bundled stand.

It cannot compete against Asus’ flagship Xonar Essence MUSES in terms of sound quality but STU is good for music lovers who have a limited budget but want a DAC/headphones with good sound quality.

STU offers clear sound with a 120dB signal to noise ratio (SNR), a powerful 600ohm headphone amplifier, asynchronous USB audio and swappable Op-Amps for DIY sound modification. It uses precision clock tuning technology further enhances audio fidelity.

STU is easy to set up. You simply connect it to your computer’s USB port, using a provided cable. Then you install the driver program from a companion CD and you are ready to enjoy Hi-Fi music from your compute with your headphones.

The unit also comes with optical input and coaxial input port for connecting to other sound sources such as a DVD or Blu-ray player to use STU to decode and amplify music for your headphones.

It has a 6.3mm stereo connector at the front and the package comes with a 6.3mm/3.5mm adapter for using with most headphones that use a 3.5mm jack.

As an external device, STU offers readily accessible controls with no need to go into software menus. You can switch between low and high gain settings, accommodating better listening experiences across a wide range of headphones, from in-ear headsets (typically 16ohm-32ohm) to premium full-size headphones (up to 600ohm).

It also has a headphone volume control knob at the front for adjusting sound level. You can also connect the DAC to your home stereo system or active speaker system using the unbalanced RCA output (line-out) and the unit also has a separate volume control knob for the speaker output.

STU also supports bit-perfect playback, which is loved by music purists. The bit-perfect playback is aided by support for ASIO audio drivers.

To enjoy bit-perfect playback, you need to install Foobar 2000 music player program and then you will need to select the program’s output device to be ASIO: Xonar Essence STU ASIO. Unfortunately, the manual of the DAC does not tell about this. Anyway, it is not difficult to do but if you don’t know, you may have to search how to do it on Internet or ask your expert friends. When the DAC receives the bit-perfect signal from your computer, its Bit Perfect LED will be lighted up.

I tested the STU with my Sony MDR EX-1000 premium in-ear headphones. I was impressed in music clarity reproduced by the DAC. I used an ASIO driver with Foobar 2000 and enjoyed listening to the songs for hours.

For example, the saxophone sound of “Sax for Sex – Beautiful Night” was very sweet with a lot of details from other music instruments. The voices of vocalists on the album “Best Audiophile Voices V” were also very sweet with good detail in the instruments.

Asus explains there are some secrets behind the good music quality. First, STU embeds a precise clock tuning IC that kills jitters prior to signal processing, ensuring the highest fidelity with extensive detail and lively sound imaging.

And it uses high fidelity Texas Instruments PCM1792A DAC to deliver accurate digital-to-analog conversion, audio clarity, and low distortion.

The circuit board also uses WIMA FKP2 and Nichicon Finegold capacitors for delivering balanced and rich sound. And it uses balanced PCB layout for symmetrical analog output path to ensure balanced and truthful representation of all sound sources and minimal crosstalk.

For the headphone amplifier section, STU uses the renowned TPA6120A2 headphone amplifier, which supports up to 600ohm impedance. It uses Texas Instruments NS-LME49720 and NS-LM4562NA Op-Amps (operational amplifiers) to deliver acoustics fine-tuned by audio engineers to support livelier, more detailed, and more spacious sound.

And STU has been designed in a way that allows advanced users to replace three swappable Op-Amps to adjust tonal performance based on personal taste. This open-ended and customisable design is inherited from previous Xonar Essence audio products, and remains true to the series’ commitment to accommodating audiophile preferences.

For advanced users, STU also provides a jumper switch to re-route sound and allow STU to be used as a pre-amplifier in conjunction with a dedicated power amplifier. 

This allows you to adjust master volume directly on the power amplifier without having to reach the STU controls.

ASUS Xonar Essence STU retails for Bt12,900.

 

 

Key specs

_ Interface: USB 2.0 

_ SNR: 120dB

_ THD+N: 0.00032%

_ Frequency response: 10Hz-48kHz

_ Analog Playback Sample Rate and Resolution: 44.1K/48K/88.2K/96K/176.4K/192KHz @ 16bit/24bit

_ ASIO Driver Support: 44.1K/48K/88.2K/96K/176.4K/192KHz @ 16bit/24bit Main chipset: DAC: TI PCM1792A

_ Headphone amplifier: TPA 6120A2 

_ Headphone amplifier impedance: Up to 600ohm

_ Swappable Op-Amps: I/V: 2x LME49720, LPF: 1 x LM4562NA

_ Additional features: Asynchronous USB interface, bit-perfect ASIO support

_ Operating system supported: Windows 8: 32bit/64bit; Windows 7: 32bit/64bit; Windows XP: 32bit/64bit; Mac OS X

_ Accessories: 6.3mm to 3.5mm stereo adapter x 1, Driver CD x 1, Quick Start Guide x 1, USB cable x 1, Power cord x 1, Power adapter x 1