Using a computer as a source for an audio system is an increasingly common method of making a cost effective digital server cum transport. In recent years the sophistication of both the playback software available to users and the USB decoding options to connect them to have increased dramatically as well. Where USB was once a fairly crude method of transferring audio, it has developed into a very reliable and extremely high quality method of doing so.
Most of the development of USB as an audio transmission format has fallen to audio manufacturers. This is logical enough - USB is being developed to do all manner of things more efficiently and many of these innovations are of more day to day worth than transferring a tiny percentage of total music sales. What you see here though is a computer manufacturer making the move into audio components. More unusually still, the product that they’ve produced is no ‘by the numbers’ device either. The Asus Xonar Essence One boasts an impressive technical specification, unusual feature set and distinctive styling. Can it deliver against the more conventional industry offerings?
The first is that the Asus doesn’t have one volume control but two. The ‘main’ control adjusts the output of the XLR and RCA outputs on the rear panel. The second is a dedicated remote for a pair of headphones. This is unusual in itself but still more radical is that the main volume is a standard potentiometer rather than a digital control and that it is permanently engaged as part of the circuit. This means that the Asus really is a digital preamp rather than a DAC with a volume control and in use it feels more familiar than some of the devices with digital volume controls.
The second is that the Asus has been designed with some very challenging headphones in mind. Asus claims that the output can handle headphones with resistance of up to 600 ohms. To put this into some form of perspective, no headphone I have reviewed for AVForums (or indeed anywhere else) would technically be beyond the Asus to drive and pretty much every headphone on the market at any price is going to be something that the Asus can handle. Most DACs with headphone amplifiers really have them as a convenience feature but the Asus goes toe to toe with dedicated headphone amps.
The Asus should still be thought of as a DAC because the decoding element of the design is also extremely extensive as well. The decoding engine is built around the Texas Instruments/Burr Brown PCM1795 chipset but the implementation is bespoke. The Asus is an upsampling design and boasts an 8x algorithm (which although they claim is a world first is likely to be contested by Cambridge Audio, Cary Audio and Simaudio to name three of the top of my head). This means that a 16/44.1kHz signal from a CD will be upsampled 8 times to an output of 32/352.8kHz. What is unusual about this is that the sampling rate stays native to the incoming frequency. Switch to a 16/48kHz signal or multiple thereof and the final upsampled rate will be 384kHz. Exactly how much harm ‘forcing’ a sampling rate from one multiple to the other is open to question but it is impressive that Asus has gone to the effort of supporting both. Incoming signals are supported at 16/44, 16/48, 24/48, 24/88.1, 24/96. 24/176.2 and 24/192kHz. Interestingly, the upsampling can also be turned off. This is normally indicative that the manufacturer believes it does make a difference and that you can hear it too.
The USB input of the Asus is controlled by a bespoke driver which besides coming on a hilariously unbalanced CD which sounded like a chainsaw on both computers it was used on to install, was hassle free to get going. This allows for the Asus to establish a bit perfect ASIO connection with suitable software on your computer. As you might expect from a PC manufacturer, exactly what happens if you plug the Xonar into a Mac is unclear but given that the unit won’t work without the driver and the driver seems to be Windows only suggests that this is a PC only device.
In connection terms, the Asus supports one coaxial, one optical and one USB input and can output them to XLR and RCA analogue outputs and the headphone socket. There is no digital output to act as a sampling rate loopthrough and the analogue output cannot bypass the volume control which means that in comparison to more conventional DAC’s, the Asus can seem slightly limited.The fit and finish of the Asus is excellent though and it feels extremely substantial and weighty- thanks in no small part to the sizeable power supply that provides the horsepower for the headphone output.
The looks are going to be something that divides opinion somewhat though. The Asus doesn’t really look like a DAC and is more visibly reminiscent of a preamp. The most visually arresting feature of the design is the mythical drawing of a tiger on the top panel. This looks vaguely like a tribal tattoo and, while different, might not be what everybody spending £350 on a DAC is after in design terms. I rather like it but I’m less keen on the contrasting silver controls on black equipment which I think ends up looking a little gaudy and unsuitable. The controls themselves are logically laid out and easy to use.
The first phase of testing with the Asus was done purely as a headphone amplifier. It was connected to my Lenovo ThinkPad and run with headphones including the Harman Kardon BT, Grado SR60i and earphones such as the Musical Fidelity EB-50 and XTZ Earphone 12. Music replay software included Songbird, Spotify and Bandcamp.
For the second phase of testing, the Asus was connected to a Cambridge Audio 851A which can be made to function as a power amp, allowing the main volume to be more effectively tested. Speakers used in this testing phase included the Acoustic Energy AE1 Classic and the Guru Junior - the review of which will be published later this month.
The final aspect of testing was to run the Asus with my wife’s Packard Bell laptop to test the ASIO driver installation with Ableton live and Kontakt plugins. This is a stiffer test of the ASIO function than most audio replay software and an effective way of finding out how good the implementation is.
The first experiences of the Asus as a headphone amplifier were very positive and suggest that the efforts that have been put into the headphone section are worthwhile. The power in reserve that the Asus has with any of the headphones I had at my disposal suggests that there isn’t much on the market it won’t be able to achieve a decent volume level with. Compared directly to a Cambridge Audio DacMagic Plus, there is volume on offer here that the Cambridge can’t get near.
Listening to a lossless download of Fanga & Abdallah Guinea’s Fangnawa Experience, the Asus is packed full of sonic detail and sounds powerful and exciting. This North African ‘Gnawa’ guitar style is all about complex rhythms and pinpoint timing and the Asus captures this with style and conviction. The bass in particular is excellent. It has extremely commendable low end detail and real impact and matches this with a speed and agility that gives the music a life and realism that is very enjoyable.
The tonality is good too. The detail and texture of voices and instruments is generally very consistent and partnered with the Grado SR60i’s that also excel in this regard, there is very little that can manage the same vivid and tangible presentation at the same cumulative asking price as this pairing. Switch to the more conventional work of Martha Tilston and the effect is still lively and vivid but it manages to slow down to better suit the more relaxed style of the piece.
The Grado (and the similarly sensitive Musical Fidelity EB-50) shows up a small issue with the volume pot on the Asus though. Pots of this nature are sequential - they engage in one channel and then the other - and at low levels this can lead to channel imbalance. The more you fork out for a pot, the less of an issue this should be. The one fitted to the Asus is extremely good but because the amp behind it has so much grunt, with sensitive headphones you wind up using it right at the bottom of the volume control and this means that a degree of imbalance is audible.
Placing the Asus in a more conventional audio system was less unconditionally successful than using it as a headphone amplifier. Connected to a Cambridge Audio 851A, the Asus has much of the same sonic characteristics as a DAC as it does as a headphone amplifier but as a line level device I really don’t like having a second volume control in play. With the volume set to maximum (and thus technically out of circuit), the output seems rather high with it in this setting - compared to other line level devices. This meant I tended to wind the volume back to roughly the same point as the other line level sources I have to hand.
With the 851A preamp bypassed and working into a fixed input, the result is more reassuring and more akin to the performance as a headphone amplifier. The Asus has the same powerful and lively sound as it does via headphones and the impression is consistently one of very well sorted digital indeed. Switching between the upsampling and the native sampling rate was interesting because it seemed to work in reverse to other experiences of switchable sampling rates. The better the recording, the more effective the upsampling proved to be. Anything that sounded thin or bright at the normal sampling rate tended to sound thinner and brighter when upsampled but high quality recordings generally experienced a small but worthwhile step forward in terms of space and soundstage. This wasn’t defined by the sampling rate either. A well recorded album on Spotify like Bellowhead’s Broadside sounded better when upsampled than the 24/192k version of R.E.M’s Out of Time which is one of the most eloquent demonstrations that simply because a file is high res that it automatically sounds any good. At the very least, the Asus allows you to switch between the modes.
The problem I have with the Asus’ performance in this regard is that the number of ways you can use it as a preamp will depend on whether you are building a new system around it or trying to fit it into an existing one. As a possible control point for active speakers, it shows huge potential but connecting it to a device with another volume control is less effective and it really would benefit from a volume bypass.
The final tests using the Asus as a USB DAC connected via ASIO to Ableton live were more successful however. The driver was easy to get going with the software at hand and proved stable and effective once running. Left for an afternoon with my wife who as a composer and musician is looking for a slightly different presentation to me generated some interesting feedback. Compared to the exceptionally flat and neutral response of the Cambridge Audio DacMagic Plus, the Asus seemed to be slightly brighter and more forward but some test tones and other response sweeps suggested that the response is equally flat - simply a little more ‘well lit.’
- Excellent decoding with a powerful and lively sound
- Superb headphone amp
- Solid build
- Volume control constantly in the circuit when used at line level
- Won't flatter poor recordings
- No shortage of competition
Asus Xonar Essence One DAC Review
The Asus Xonar Essence One is a genuinely surprising product in a number of ways. It would have been easy for a company making a first foray into the hi-fi market to play it safe with a relatively conventional product. That they haven’t is to be commended and depending on your requirements Asus has gone and made a device that in some areas is exceptionally capable.
If you are looking for a straightforward, line level DAC, the Asus is less convincing. The presence of the volume control in the circuit at all times and the fact you are paying for components that you won’t be using, makes it less convincing. The very distinctive set of design decisions that the company has taken mean that this is not an absolute all rounder and if I was shopping for a line level DAC at this price point this is probably not the one I’d choose.
If you are looking for a headphone amp for digital sources though - be they USB or electrical digital - this is a must audition product. The Asus combines the performance and power handling of a dedicated headphone amp with excellent digital decoding. I don’t believe there is pair of headphones under £1,000 that they won’t do justice to. This is an exciting and thoroughly musical performer that is very enjoyable. Equally, if you are looking to connect the Asus to a power amp or pair of active speakers, the same basic traits seem to stay present and correct. The experience that Asus has with USB is clearly apparent and this is a product full of technical knowhow. This product won’t be all things to all men but it could be exactly what you need.
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