Performance and Testing
Performance with music will be covered in three categories; Performance with MP3 (256+) encoded music, WAV encoded music and CD quality without any compression so to speak. First up let's have a listen to how the Xonar handles MP3s of reasonable quality, definitely an area that will be important to potential buyers of the card.
I began my MP3 testing with some progressive metal, which encompasses a lot of spacial instruments while still having a driving beat to keep things on track. Overall, I found MP3 reproduction to be of an impressive standard with a more dynamic feel to the overall sound compared to my SB Live!. When dropping the quality to 160KHz, while noticeable the Xonar's musicality brushes over this with far greater ease than my SB Live! ever did.
When auditioning a WAV file things (as expected) only get better due to an inherently smaller amount of compression used in this format and the Xonar's superior DACs (Digital To Analogue convertors). The reality is when you combine a card of this quality with your usual MP3/WAV files there really should not be a great deal to complain about, as all that is asked of the Xonar is to "read" the compressed file and then convert it into an analogue signal, ready to be sent to the speakers with as little added to the signal as possible. I feel the Xonar does this as well as any card I've used before.
When playing back 'real-time' audio from a piece of digital media (CD/DVD) the card's ability to sample the signal frequently with a good resolution becomes important. Don't forget an MP3 has already had a 'picture snapped' of it and can only be read, where as a real-time audio feed must have 'snap-shots' taken at regular intervals; just like a camera, the more information taken with each snap the greater the overall picture and the more detail made visible (or audible for arguments sake) to the user. That's basically the theory behind sample rates and bit depth.
Ok, so if we have a 96KHz/24-bit sample rate (supported by the Xonar) then the card is taking snap shots of all the frequencies up to 96KHz with a resolution of 24-bit (don't forget this is binary - i.e. 8/16/24/32 with 32-bit - 192KHz being the highest resolution currently supported).When using lower sample rates the nyquist frequency comes into play - i.e. a sample rate of 44.1KHz can only capture frequencies not above half of this figure, which would be 22.5KHz, theoretically above the threshold of hearing but it has been proven that we are aware of frequencies above this, thus requiring sample rates up to 192KHz.
Control over the card's sample rate is found within the control suite and can be stepped accordingly. Of course there is little point telling the card to sample a 128k MP3 at 192KHz as the data is already lost once compression is added so this must be taken into consideration. However some DVDs do support 96KHz/24-bit sampling in which case it is necessary to alter the sample rate accordingly.
When listening to an audio signal that has not been compressed the Xonar begins to stretch its legs, delivering a crisp and airy reproduction of the streaming signal with spacial characteristics that are truly impressive. I feel also as an important factor the card's very quiet signal-to-noise ratio of 118db is contributing to the impressive dynamic response. Dynamic response is the difference between the loudest and softest sounds in an audio signal, and also how quickly the response is to these extremes, i.e. a megaphone will have a poor dynamic response as its only intended to 'boost' the range between 1-5KHz where the human voice appears for the most part, with frequencies above and below being left alone, thus providing clear representation of voices but little else in the audible spectrum.
I found reproduction of full range streaming audio to be comparable to more expensive equipment when using my Logitech z5400 digital surround system, and certainly some of the cleanest most transient sound I've heard since the Videologic X-fires paired with their in-house Sonic Fury board many years ago.