Audio/Video, Hardware, Mobile Computing, Reviews

ASUS Xonar U7: An Audio Upgrade for All

xonar u7

Mainboard manufacturers always push the latest and greatest integrated devices, but onboard audio is often left behind. The generic “HD Audio Device” chip is king, supplying the very basic multi-channel options and sample rates — disregarding the infrastructure, component quality, and connectivity that makes a true audio device.

For consumers that don’t want to settle for lacking audio quality, finding a value product without making compromises is difficult.

Enter the ASUS Xonar U7

Luckily, ASUS’ Xonar U7 USB sound card is an on-point choice for sound performance, features, and simplicity, all for a under $100. As a 7.1-channel sound card, headphone amplifier, and DAC in one, the U7 is an integral member of the Xonar family. Everything fits into a compact chassis, great for computing on the go, or even as a low profile desktop unit.

Besides the golden color trim, the U7 is unassuming at first. But what lies inside the U7 is what really makes it shine. Let’s take a look:


A single dial on top controls the volume of all “Headphone”, “Speaker”, and “SPDIF” outputs, which are toggled through by pressing down on the dial. The same knob controls volume on every source independently, so switching from Speakers to Headphones doesn’t blow out your ears. The U7 can even detect when headphones are plugged in or unplugged, and immediately switch between outputs.

On the front sits a 3.5 mm Headphone port, bridged to an integrated amp suited for 32-150 Ohm impedance. This is crucial for headphones that require more power, to deliver accurate reproduction at higher volumes. It may not be able to properly drive, say, Sennheiser’s HD 600 and above (300 ohm impedance), but can still accommodate a wide variety of music, reference, and studio models.

Some enthusiasts would complain that the Xonar U7 does not have a dedicated, full-size 1/4″ port. But due to its compact size, there was most likely no space to comfortably fit the component. It may be a deal breaker for some, but this is easily solved by using a proper adapter.

Next door is a Mic/Line input jack, which supports any 3.5 mm computer microphone, and is useful for your gaming headphones’ mic too. There is a dedicated microphone volume control alongside the port, for easy adjustments without having to dive into Windows settings.

The same input can also detect line-level sources (192 kHz/24-bit) like music players or instruments, for recording and even for listening. Enable the “Listen” functionality for the Xonar U7 Line device, under Windows’ Sound Properties, and you can route your favorite music player directly to speakers.

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Finally, the important I/O panel on the back. Starting from the left, R and L outputs (RCA), Side Surround (7.1), Center/LFE, and Rear Surround outputs. Because this is a USB device, these are not amplified outputs, so you’ll need powered speakers (more about that later).

Next is the SPDIF port, for both coaxial and optical connections, with an included TOSLINK adapter. The controller supplies PCM, Dolby Digital, and DTS standards to AV receivers and home theater systems, for up to 7.1 channels.

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Finally, there is a Type-B USB 2.0 connector that plugs into your system. There is also switch on the bottom with a selector between “USB 1.0” and “USB 2.0”. This should be already set to 2.0, and your system needs to provide a fully powered port for full functionality and performance. Why there is even a choice is anybody’s guess, but ASUS claims this backwards compatibility can still supply 7.1-channel playback up to 48 kHz/16 bit sampling.

A Quick look inside

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The Xonar U7 uses the popular Cirrus Logic CS4398 stereo DAC for headphone output (120 dB SNR), a CS5361 chip for A/D input handling, and a CS4362 multi-channel DAC (114 dB SNR) for all other outputs — pretty impressive for its overall size. At 0.0006%, total harmonic distortion/noise (THD+N) is also kept to a minimum, keeping outputs as clean as possible.

Controlling it all is a C-Media 6632A Audio Processor, a Class 2 USB audio chip fueled by its own dedicated DSP and drivers. Combine these chips with all Japanese solid-state capacitors on top of a 4-layer grounded PCB, and you have a device that’s built to last.

All outputs are capable of sample rates up to 192 kHz/24 bit depth, expected from a current HD audio device. However, when it comes to sampling, keep in mind that there is very little 192 kHz content out there to appreciate (or even notice the difference). For ASUS Xonar, this is more about numbers marketing than actual benefits. Higher sampling is useful for capturing music, but even mastering-quality “true vinyl” rips are encoded at 96 kHz / 24-bit.

For a product that only runs on 5V / 500 mW of USB power, the U7 packs a bigger punch than most discreet audio solutions, while also removed from the EMI-noisy environment inside a computer. The components inside aren’t the best in the market, but definitely a bargain for the U7’s price point.

Getting the Xonar U7 up and running is simple…

…but there may be a few bumps on the road.

After connecting it to your system, you need to install drivers from an included CD. Those who don’t have an optical drive need to download it from the ASUS support site. Instead of a standard .ZIP file, ASUS provides a .RAR archive for download, which isn’t native to Windows, and needs third-party software to access.

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The U7 is compatible with Windows 8.1 64-bit down to XP. While there are no official drivers for Mac, it can still run off generic USB Audio protocol on OSX 10.6+, at least as a headphone DAC/amp up with full sampling.

From there, you have a variety of output connectivity to choose from. Stereo headphones, 5.1 headphones, 2 channel analog speakers, 4-7.1 channel surround — the choice is yours. However, keep in mind that all of the rear-panel analog outputs are passive, and you may also need RCA adapters to plug in the L & R speakers.

So if you have an existing system for your desktop, like a Logitech surround set, you’ll still need to use its power control and therefore, gain stage two different knobs to set your levels. The same is true for reference studio monitors, which need to be powered and tuned properly for accurate mixing. I recommend playing a song, setting the U7 volume to ~90%, then slowly increase the speaker control to its highest comfortable volume without distortion, then only adjust the U7 from then on.

This is probably the only downside of the Xonar U7, but only because of USB power limitations. As a mobile DAC and headphone amplifier, there are less potential headaches.

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Packaged with the drivers two different DSP suites – Xonar and Dolby. The “U7 Suite” controls settings for every source individually, including speaker setup, sample rates, and your usually unnecessary “environmental effects”. While in Headphone mode, you can adjust the U7’s built-in amp gain from -12 to 0 dB, depending on your headphone impedance.

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The “Dolby Home Theater v4” suite is loaded with profiles of different EQ curves, volume leveling, and surround visualizations. The “Volume Leveler” setting has a similar feeling to the “Crystalizer” effect heard on Creative audio cards. This compression/excitation effect could give your music and games an extra oomph, but when reference listening and mixing audio, all effects can be disabled by accessing the Dolby taskbar quick menu.

Music, gaming, studio monitoring, and more

The Xonar U7 has you covered.

Being able to at least hear clean, properly driven 24-bit sound is worth the price tag alone. Audiophiles may have more discerning requirements, but this could also make a great gift for friends who haven’t yet experienced the difference. Enthusiasts will pay hundreds, if not thousands on graphics and computing hardware – why leave audio behind?

Music, no matter which output you choose, sounds great on the U7. Without all the DSP effects, you can still enjoy clean, unbiased digital audio. It may not be able to properly drive audiophile-class headphones or passive monitors, but it can improve most consumer or prosumer setups. Even the Line-in passthrough has independent A/D conversion, so I can route content off of portable FLAC players, like the Astell&Kern AK100, with minimal information loss.

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As mentioned before, you may need to experiment with speaker gain staging, because all rear analog outputs on the U7 are passive. Regardless, all genres of music shine with the U7, it just comes down to your headphone or speaker choice.

Gaming audio is also improved, especially if surround speakers are in play.  Surround channels are usually not provided as much power as other channels on discreet solutions, to discourage EMI. With an external device like the U7, there are much stronger signals to the surround L & R channels.

For headphones, the U7 can handle your favorite stereo pair, or even true hardware surround models, and provide a clean digital source. Most current games, especially FPS titles, already use upmix algorithms that provide virtual surround stages for stereo headphones. So using the C-Media Xear or Dolby effects in the included suites, which realistically only adds the “room” back into the mix, is unnecessary.

This product isn’t marketed for studio or reference accurate listening, but it’s still an option for those getting started. RCA connections (front left and right speakers) are unbalanced, but this is rarely an issue for short distance cabling. The U7 could properly send signal to a pair of Yamaha HS8 powered studio monitors, without distortion or a noticeable noise floor at comfortable volumes.

As a DAC, the U7 is also ASIO (Audio Stream I/O) compliant, providing low-latency interaction with sound/music editing applications. Users can choose between 16 and 24-bit, and as low as 4 ms latency.


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When we add up its rich audio processing, connectivity, features, and compact size, the Xonar U7 has exceeded our expectations, especially at a MSRP of $89.99. At a fraction of how much you would invest in quality graphics, there is practically no reason why you should settle for onboard audio today.

And for that, BSN* is awarding the Xonar U7 with our Editors Choice Award.