[Frederik S]

Introduction

ASUS has been putting a lot of effort into making some decent sound cards over the past years, but it still came as a surprise to many that they have gone into the DAC & headphone amplifier business. ASUS's bid to conquer the DAC & amplifier market is dubbed the Xonar Essence One which features 192 kHz playback capability, asynchronous USB, and a headphone amplifier section with swappable op-amps. It also has an upsampling feature which we will discuss further on in this review.

It is clear that ASUS aimed for the higher end market with this solution and as it stands now the retail price for the Essence One will be a somewhat high €420/$550. Compared to their line of quality integrated sound cards this is a rather high price premium, however, they are two completely different breeds.

The Essence One's design is quite nice and the implementation of both USB transport and DAC section seems top-notch. The headphone amplifier section is likewise of a quality that is in a different league compared to that featured on internal ASUS sound cards. This is of course due to the very different design envelope, being an external unit both the power source and size are pretty much unlimited which allows for a more ideal construction, mechanically as well as electronically.

Feature wise the Essence One is a beast, its main competitor on the market looking besides the semi-stationary HiFiMAN HM-801 is the Cambridge DACMagic II.

Specifications

• Output Signal-to-Noise Ratio (A-Weighted) (Front-out):120 dB
• Output THD+N at 1kHz (Front-out): 0.000316 %(-110 dB)
• Frequency Response (-3dB, 24bit/192KHz input): 10 Hz to 48 KHz
• Output/Input Full-Scale Voltage: Balanced Output : 4 Vrms ( Vp-p), Unbalanced Output : 2 Vrms ( Vp-p), Headphone : 7 Vrms ( Vp-p)
• Audio Processor: C-Media CM6631 High-Definition Sound Processor
• Analog Playback Sample Rate and Resolution: 44.1K/48K/88.2K/96K/176.4K/192KHz @ 16bit/24bit
• S/PDIF Digital Input:44.1K/48K/96K/192KHz @ 16bit/24bit
• Analog Output Jack: 2 x 3.5mm RCA, 6.3mm, 2 x Balanced Output (XLR),
• Input: 2 x Digital S/PDIF Input (1 x Coaxial, 1 x Toslink), 1 x USB
• Dimensions: 261.33 x 230 x 60.65 mm ( L x W x H )

The Package

The ASUS Xonar Essence One ships in a mighty big box. It is well padded which is needed. The unit is quite heavy due to the casing design and the huge toroidal transformer.


Contrary to most mid-end headphone amplifiers and DAC the Essence One has an in-board power solution. It is capable of receiving both 110 and 230 V so the unit can be used anywhere in the world.

Closer Examination

ASUS's style is debatable, it is certainly not the prettiest unit on the market and the many blue LEDs just look a bit misplaced, definitely not what you would expect to see on a $600-ish performance headphone amplifier.


The logo on-top is the golden dragon we have seen on a lot of ASUS sound products. Oddly enough the top part is curved making it impossible to stack something on top of the unit. The surface coating system used makes it a bit of a finger print magnet, fortunately the coating is well executed and will probably last a very long time even with regular cleaning.


The business end of the ASUS Xonar Essence One is relatively well laid out. The placement of the headphone jack is good, but the small headphone volume knob is quite hard to reach when you have inserted a headphone with an over-sized 1/4" jack. It would be better if the central digital volume controller and the headphone volume controller were swapped, since it is unlikely that there is anything plugged into the headphone out while the digital out is in use.


Again the layout is semi-cramped, but looks alright. The knobs have a very average feel to them and it is hard to adjust them properly.


This ASUS unit has a lot of good connectivity options at the back. You get balanced outs, digital in via optical and coax, and a set of RCA outs as well. This is really good considering the price of the unit. Kudos for including balanced outs, I am sure that a lot of people with active speakers will find good use for them.


The back side of the Essence One is well laid out. The unit is passively cooled therefore the back plate is perforated.


ASUS's design oddities do not stop with the curved top plate, also the bottom is profiled which again makes the unit a bit harder to stack. The small natural rubber feet are OK, but it would have been nice to see something beefier that provides better vibration reduction. Given that rubber feet do not cost a lot it seems a bit odd to skip this upgrade from a manufacturing point of view.


With the top off you can see where ASUS's design focus was with this unit. The components used are of a very high quality throughout the unit, and the many swappable op-amps are a delight for tweaking audiophiles.


The Burr-Brown PC1795K DAC in the unit is one of the best sounding on the market today, and it accepts 192 kHz / 24-bit which makes it capable of converting the highest quality source material available online.


ASUS uses an Alpha pot to control the volume for the headphone out section. The way it is integrated means that there is a channel imbalance occurring every second step, effectively halving the resolution of the volume pot. The volume imbalance is around 1-2 dB which makes it noticeable through the headphones. Since the imbalance is present throughout the volume control's reach it is an extremely annoying bug, especially when you are using high sensitivity headphones.


A relatively big toroidal transformer powers the unit.


Clicking the image above gives you an ultra-high resolution stitched image for those that want to see the details. The NN5532s are swapped for LM4562NAs on the picture above, otherwise it depicts a stock Essence One.

Performance

The performance of the ASUS Xonar Essence One is tested both via listening tests with a barrage of headphones and a set of RMAA tests carried out by hooking its headphone out up to a ASUS Xonar Essence STX sound card with the latest drivers installed. The STX was setup according to the guide on RightMark’s webpage.

RMAA

RightMark Audio Analyzer is by all means an obsolete piece of software, but it still provides good enough results to be able to judge some of the core qualities of a DAC and headphone amplifier. The Essence One provides a neutral output and features a cut off at the 20 kHz mark. It is linear all the way to the bottom of the audible spectrum in an unloaded scenario. All measurements give the unit a score way above average and all the measurements are in line with what you would expect from any high-end DAC and headphone amplifier combination.

The sound card used for the test was an ASUS Xonar Essesnce STX which of course has its limits when it comes to measurements. The measurements provided by ASUS in their Audio Precision report concurs on a number of aspects with what we saw on the RMAA test, except for the THD + N measurements which Audio Precision reveals is in the range of 0.000316% (-110 dB) the discrepancy is most likely due to RMAA in conjunction with the Essence STX.

Listening Tests

Before any listening was done the unit was updated to the latest firmware, this process is a bit tedious since there are essentially two sets of firmware on the device. One for the USB receiver and, one for the rest of the unit. After the update was done the unit was allowed to play for 100 hours before any critical listening was done.

For this particular test we brought out the big guns to see what this unit it capable of, the following headphones were used for testing: Sennheiser HD600/HD650/PX-200II, BeyerDynamic MMX300 (DT770 32 Ohm version), HiFiMAN HE-6/HE-500/HE-400/HE-300/HE-5LE, Westone ES5/W4R, Ultimate Ears In-ear Reference Monitors, Jerry Harvey Audio JH|16Pro, Fostex T50RP (slightly modded), Grado SR-60 (slightly modded),

Since ASUS is kind enough to enable op-amp swapping on their higher end headphone solutions we thought it would be fun tryout LM4562s and OPA 2604AP instead of the stock NE5532, and AD 797BRZ instead of the LM49720NAs.

The Essence One brings a lot of neat features to the table. For one it has 192 kHz 24-bit playback (4.35 times the resolution of a CD content) and features a well implemented USB interface. In order to kick off our testing Foobar 2k was fired up and ASIO drivers configured to get the most out of the unit. Even straight out of the box the Essence One proves to be an entertaining piece of kit. Through ASIO support the unit can change sampling rate per track in Foobar almost instantaneously which is great since HD music files rarely feature the same sampling rate. In our test library we had content mixed across the following sampling rates: 44.1, 88.2, 96, 176.4, 192 kHz (16/24-bit). The Essence One eats them all without any issues or awkward artifacts appearing which is to be expected of such a relative high-end piece of kit. It does have a slight pre track judder sometimes but that is most likely due to Foobar 2k and its ASIO plug-in.

With the standard op-amps installed the unit simply outdoes the HiFiMAN HM-801 on all accounts, right from 44.1 kHz to 96 kHz which is the highest sampling rate the HiFiMAN player can handle. Sonically the two units are very different sounding. The HiFiMAN has an early roll-off which gives it a somewhat soft sounding high-end, bass control is tremendous with both units and the HiFiMAN player's balanced module gives the ASUS Xonar Essence One a real run for its money bass definition wise. Comparatively the midrange of the Essence One is more detailed albeit slightly less spacious sounding with the stock op-amps in the unit. Both the HiFiMAN HM-801 and the Essence One is capable of driving quite demanding headphones like the Sennheiser HD650s and the HiFiMAN HE-5LEs without breaking a sweat, however, the Xonar Essence One provides more headroom in terms of volume due to a slightly higher default gain setting.

Compared to the ASUS Essence STX sound card which is considered a good mid-end source for headphones the Essence One is just better on all accounts. The STX sounds coarser and the sound stage is a far cry away from being up to the same standard of the Essence One. These two products are miles apart in terms of sound quality, even though the STX sound good by all accounts. Depending on the headphones in use the differences vary in size. With a set of high end headphones like the HD600s or HD650s the differences are easily noticeable and the same thing goes for the HE-400/HE-500s. Going back to a set of BeyerDynamic MMX300s, Sennheiser PX 200-II and HE-300s the differences are less apparent albeit the difference in sound stage dynamics are still very present.

Interestingly enough our much loved Fostex HP-P1 proved its worth albeit being limited by only being able to decode 44.1 kHz content. Its organic and smooth presentation is up there with the HM-801 and with the filter set to option 2 you get almost the same kind of liquid like sound as the Essence One provides with the LM4562s and the AD 797BRZs installed. The Fostex HP-P1 is only let down by its detail level with 44.1 kHz source material. The Essence One is just some much more effortless in producing micro-details and delivering a coherent and spacious sound.

The gain of the Essence One is quite high making it less than ideal for use with ultra-high sensitivity in-ears. Even with the volume at its lowest balanced level we had to turn down the volume in Foobar in order not to damage our ears.

The stock op-amps are alright, the use of NE5532s for the I/V and filter stage and LM49720NA for the headphone amplification stage does the trick and gives the sound good balance. Some might find the neutral sound of this particular combination a bit boring, but luckily you can induce a warmer sound signature by opting for some slightly higher end op-amps for the filter stage and some notoriously hot sounding op-amps for the headphone gain stage.

Our first experiment with op-amps was a simple job of pulling out the NNE5532s and loading the device with six LM4562NAs and this change seemed to give a better rendition of the sound stage and a better sense of layering in the sound. Particularly the midrange definition change makes the swap well worth the extra dollars in my opinion, listening to 96 kHz versions of Bueno Vista Social Clubs "Chan Chan" really highlights the change as the two male voices in the center become so much easier to tell apart spatially. The LM4562s are definitely more transparent and smoother sounding in the ASUS Xonar Essence One.

Introducing the AD 797BRZs to the headphone stage opened up the sound a bit more, but the changes are marginal over the stock op-amp. Separation and layering was a bit better and the midrange seemed to gain some much needed warmth. The highs are definitely sweeter with the AD 797BRZs installed, but the cost of these op-amps makes it a tough call. We got our dual SOIC AD 797BRZs on DIP8 adapter for around $60, which seems to be the going rate for these hyped high-end op-amps. If you are going all in and what the sound signature of the AD 797BRZs the upgrade is alright bang-for-buck wise, but it is definitely not a must have for all users. The stock ones do a magnificent job in this particular design.

Synergy wise the ASUS Xonar Essence One will pair well with most headphones since it is neutral sounding with the default op-amps. Due to the implementation of swappable op-amps you can get the Essence One to sound just the way to want it, however, exotic op-amps will be hard to find and adds to the total cost of the solution albeit providing only minor upgrades to the sound quality.

Value and Conclusion

	The ASUS Xonar Essence One DAC & Headphone Amplifier sells for approximately €400/$500 online
	Versatile Accepts 192 kHz / 24-bit over USB Swappable op-amps Balanced out-puts Multiple in-puts Headphone amplifier section capable of driving even demanding loads One unit design Good price / performance ratio
	Upsampling feature Volume control issues Blue LEDs on front Curved up and bottom plate Somewhat cramped front lay-out
9.0	With the Xonar Essence One ASUS have definitely taken the fight to the DAC and headphone amplifier manufacturers. The design provides excellent sonic characteristics and qualities and furthermore it is easily customizable. The headphone amplifier section of the Essence One is definitely one of the better out there both in terms of power but also definition, unfortunately it is paired with an annoying volume control that does not give the necessary control. Looking into the DAC section of the amplifier reveals that ASUS means business with the One. The 192 kHz / 24-bit DAC section easily bests the NOS 1704 UK setup in the HiFiMAN HM-801 and is ahead of the AKM4480 equipped Fostex HP-P1. The question on everyone's lips is of course whether or not the Essence One is worth the price difference compared to the Essence ST/STX sound cards and the simple answer is yes, for anyone with a set of high-quality headphones or studio monitors. The Essence One punches above its weight, and if you can live with some of the quirks like the somewhat annoying volume control, odd shape, and lots of blue LEDs then Essence One is brilliant value. Upsampling with the Essence One is a hit and miss, it simply does not improve anything, but it is a borderline who-cares situation since it sounds so brilliant with standard CD quality source material.