Asus product page - http://www.asus.com/uk/Sound_Cards_and_DigitaltoAnalog_Converters/Xonar_Essence_STU/overview/ OcUK product page - https://www.overclockers.co.uk/showproduct.php?prodid=SC-026-AS&groupid=701&catid=1925 Today I will be giving a quick look and thoughts on the ASUS Xonar Essence STU. A headphone amplifier built to very high standards and with some excellent key features such as, • 120dB signal to noise ratio. • High and low gain to drive 600-ohm headphones. • Hot-swappable Op-Amps. • Nichicon Fine gold capacitors used throughout. Packaging. Accessories. Included are, • EU and UK power cords and power supply • USB cable • Quick start guide and driver disk. • 6.3mm to 3.5mm adapter. • Pedestal. The Essence STU. This is not a plastic affair: everything is machined or polished metal. The construction and overall build quality is without question. The unit itself feels weighty and as if you are dealing with an exotic Hi-Fi component. The power and input selector buttons operate with a satisfying click and the two volume knobs also feel excellent. The unbalanced outputs are good for driving powered monitor speakers, etcetera. The flip-switch is to switch the gain for the front headphone amplifier jack - you have to pull the headphones out of the socket to actually switch the gain so this stops you from blowing your ear drums out by accident. And on this side are the inputs. • 3.5mm jack for phones/tablets, etcetera • Coaxial • Optical/Toslink • USB from a PC The pedestal holds the STU extremely well and is a superb snug fit. Using this you can place the STU almost anywhere. Inside the STU. The inside components are beautifully laid out with the power input well-separated away from the main audio section. Nichicon fine gold audiophile capacitors are used throughout the audio section. At the top of this picture are the three Op-Amps that make up the low pass filter and two current/voltage (I/V) converters. At the bottom, surrounded by the blue jumper switches on the left, is the "DC Servo" which filters out unwanted pop noise and controls the headphone jack. You can also see the dedicated right and left channel variable resistors (the blue squares with screws on top). The final blue jumpers seen up on the left (behind the volume knobs) is to bypass the volume control completely for use with a separate power amplifier and you would prefer to use that devices volume control instead. Performance and thoughts. I have been using this for a couple of weeks now with, • Sennheiser HD505 • Corsair raptor HS30 gaming headset • AKG K550 All in a variety of uses from film/sound listening to even just gaming. As its main focus is as a headphone amplifier that's what I concentrated on. The sound is exceptionally clear and can get to some death-defying volume levels with no distortion and remained composed throughout testing. Listing to a wide range of music types from Kate Bush/Michael Jackson to The Shamen to Drum+bass was a joy, but I do tend to prefer a bit more bass if I am being honest. The Op-Amps can be swapped out for other pairings and ASUS have lists of what to use and the effect it can have on the sound. Conclusion. The Essence STU is a well-built and good-sounding piece of kit with the ability to drive the highest impedance headphones with control and poise. Well worth a listen if you are looking for a headphone amplifier that can also drive powered monitor speakers.
Essentially a Xonar Essence STX in a box so, should sound rather good, especially as it has the usually preferred LME49720 opamps in the I/V sockets, that many of the internal card users upgrade to.
