Specifications

Details and Specifications

Let’s take a look at the specifications for the Xonar U7, shall we?  They are very good for and audio device, but just about what you’d expect for an external device free from the electrically noisy environment inside your computer.

Cut ‘n paste from ASUS’s website:

First off, this is fairly impressive specifications for a sound card powered off of 5 volts, 500mw of USB power.  Now that I think about it, the U7 has specifications that are better than a lot of discreet enthusiast sound cards.  Huh.

Same as it ever was, signal-to-noise ratio (SNR) is the primary metric for audio measurement.  It doesn’t mean something will sound good, but a good indicator of overall sound quality.  The Xonar U7 uses a Cirrus Logic CS4398 2-channel DAC for the headphone output that boasts a meaty 114dB of SNR, which after listening to it, I tend to believe the U7 is achieving close to that number. The other important measurement is the THD+N, which is basically everything else that comes out of the circuits other than what went into it.  At 0.0006% THD+N, the Xonar U7 is very clean.  A well-trained human ear can discern THD down to about 0.005%, so the Xonar U7 is well below what few humans can hear.

No specification I could find on the microphone analog-to-digital converter, short of tearing it apart (for science), but testing proved the U7 also has high quality ADC.

Connecting up the Xonar U7 requires a free USB port.  Do try to use a USB 2.0 port or above.  The USB 1.1 is rumored to not work so well.  There are two types of USB for audio, regular and asynchronous, with the latter being the most preferred type for audio.  Since ASUS didn’t make any noise in the fact chit about asynchronous USB with the U7, I can assume that it uses regular USB.  Of course it’s not that easy, there’s also USB Audio Class 2, which the Xonar U7 most certainly is, and guarantees audio up to 32-bits/384KHz.  Hey, keep your eyes open, and don’t click away to porn.

Anyway, at the heart of the the Xonar U7 beats a C-Media 6632A Sound Processor. This is not the average USB audio chip that we typically find in headsets, or even sound cards that support the driverless USB Audio Class 1. The 6632A supports USB Audio Class 2, which means it does need a driver, but it also means it has a good bit more horsepower for DSP effects, 7.1 channel surround, 24bit/192KHz sampling rates, and specifications on all things audio are much tighter.  This is a good thing.

With the added horsepower of the 6632A DSP, the Dolby Home Theatre v4 suite of technologies is supported.  These aim to solve some ‘common’ problems with audio such as encoding stereo sources to surround sound, normalizing volumes, and increasing intelligibility of the voice range.  It reminds me of Creative’s Crystallizer technology from years ago.  This also brings up a whole articles’ worth of HRTF, Dolby versus DTS, and other home theatre topics, but I’ll concede to not paying too much attention in the age of Netflix and Youtube where sound quality is just about good enough for most folks.  This is what Dolby is trying to fix.  It is my opinion that adding algorithms on the output side of audio is a noble fight, but not the best way to go about it.  Using computing power to fix audio problems during decoding will just never be as good as fixing audio quality during recoding and mixing.  Part of the problem is that the bit rates for surround sound is pretty low, 24-bit/48KHz for DVD, and for streaming, bitrates for audio can be much, much lower. 

I want to mention nVidia’s well loved SoundStorm on the nForce2 chipset. It could do DDL encoding on the fly, a feature that was novel at the time (2002-ish), and since it was included with the chipset, very inexpensive.  It was a killer feature.  Then nVidia killed it because the licensing fees were becoming too expensive.  Yes, the price of success.  Nowadays, you’re hit or miss for surround encoding, some on-board audio chips support it, and some discreet audio cards support it.  It depends on who got the best deal for the algorithms from Dolby. Well, good news everyone, the Xonar U7 does support DDL.

One feature that isn’t listed is the headphone amplifier.  The amplifier has adjustable gain settings (see the Driver section) that will help boost the volume of low sensitivity headphones.  The AKG K701 headphones, for example, are around 62 Ohm at 1KHz, which means they are a little less loud than other headphones at the same level.  Most headphones and headsets are around 32 Ohm, and of course, most home speakers are around 8 Ohm.  The U7 will handle headphones up to 150 Ohms.

In conclusion, the Xonar U7 are very well specified and already much better than what you’d get with on-board sound.  The only downside I can find is the lack of a 6.3mm (¼”) headphone output jack.  Let’s move on to the photos.