ASUS Launches Xonar Essence STU USB DAC

by Ian Cutress on 10/21/2013 5:03 AM EST


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  • richardm - Monday, October 21, 2013 - link

    The "600 ohm headphone amplifier" when they really mean "the amplifier is suitable for high-impedance headphones up to 600 ohms" is damned lousy marketing. What is the actual output impedance of the headphone amp? It's definitely not 600 ohms. Reply
  • Rajinder Gill - Monday, October 21, 2013 - link

    TPA6120A2 is used for HP output. Output Impedance is circa 10 ohms. Reply
  • ninjaquick - Tuesday, October 22, 2013 - link

    The TI TPA6120A is rated for Vmax = 30, and Wmax at 1.5, which is 600ohm. Reply
  • DanNeely - Monday, October 21, 2013 - link

    Why only headphones? The main market for a USB audio adapter is going to be laptops when used in desktop alternative. In that mode going to a full 5.1 speaker setup would be nice except that most laptops don't have enough audio out ports. Reply
  • Rajinder Gill - Monday, October 21, 2013 - link

    Xonar U7 is the 7.1 channel capable USB device from ASUS - market for multi-channel is however very small these days. Not many people like to have a bunch of cables strewn across their desktop or room. On top of that, adoption of 7.1 channel gaming oriented headsets hasn't taken off either.. Reply
  • Flunk - Monday, October 21, 2013 - link

    Most people who use multi-channel surround on a computer are using desktops. The speaker setup is so big there is little point in using a laptop because you lose so much performance for no real mobility improvement.

    7.1 channel gaming headsets are just plain stupid, they're very pricey and the speakers are so small and so close to each other. You're better off with a good pair of 2 channel headphones.
  • Flunk - Monday, October 21, 2013 - link

    As a follow up, high-end gaming notebooks actually support 5.1 or more channels natively. I have an Alienware m14x R2 that supports 5.1 analog speakers. Reply
  • stepz - Monday, October 21, 2013 - link

    People who buy $400 DACs do it for music listening. Music is stereo. Reply
  • nathanddrews - Monday, October 21, 2013 - link

    Except for when it's 5.1. ;-) Reply
  • asliarun - Monday, October 21, 2013 - link

    IMHO, special effects (in movies, games etc.) are 5.1
    Music is still predominantly stereo.

    I like the fact that this product uses decent quality components and actually has an analog volume control instead of a digital one that will shed bits.

    However, the price is too high. Compare this to some of the Audio-GD products for example. The NFB 15.32 has similar quality components, and has a better volume control implementation, supports higher resolution (32bit async USB at 384k), has dual DAC chips - one for each channel. For all this, I paid roughly half the price ($235) of the Xonar STU. (Shipping was extra though and was a hefty $50, and I paid $20 more for a clock upgrade - but still...).

  • Impulses - Monday, October 21, 2013 - link

    I agree, I bought an STX because of the value proposition. At $160 on sale (or even the MSRP of $200) it's a pretty solid value compared to most discrete amp/DAC solutions. It won't beat something like a Schiit Magni/Modi for the price (and the 10ohm output impedance is iffy with many low impedance headphones) but it'll come pretty close while being an internal solution and also providing Dolby Headphone. If you don't care about DH processing you're better off looking at stuff like the O2/ODAC, Magni/Modi, etc. At $400 this competes with a higher class of audiophile products. Reply
  • ninjaquick - Tuesday, October 22, 2013 - link

    This is a stereophile device. There are other products for Surround enthusiasts, but those are far less relevant as most Audiophiles don't care about reproduction of surround sources, as most surround sources push most content to center/FL/FR channels, leaving all other channels for strictly surround cues. Reply
  • maecenas - Monday, October 21, 2013 - link

    I've really enjoyed my ST card from Asus, great to see they're providing the same card in an external USB format, but I don't see what justifies this being twice as expensive as the ST/STX cards. Reply
  • extide - Monday, October 21, 2013 - link

    I have said this before and I will say it again. I will only be interested when they stop using off the shelf IC headphone amps. Build a proper discreet amp, then you are talking. At least it is using a burr-brown DAC, but I am a little bit partial to wolfson these days, but that's just me. I am sick of seeing that TI TPA6120A amp though!!! Reply
  • extide - Monday, October 21, 2013 - link

    I forgot to add, the rest of it looks pretty well done though. I like the ability to bypass all amp circuitry and use it as just a DAC, and the rollable op-amps is a nice touch as well. They are definitely on the right track here, just get rid of that damn TPA6120 and I will be a lot happier. Reply
  • extide - Monday, October 21, 2013 - link

    God I didn't see the price! I currently run an ODAC + JDS Labs C421 HP Amp, and together they are cheaper than this thing's MSRP! Reply
  • moriz - Monday, October 21, 2013 - link

    sounds like a discrete amp is exactly something that you DON'T want.
  • extide - Monday, October 21, 2013 - link

    That guy knows his stuff for sure, but he is talking about going discreet to the point where you arent even using op amps, I wasn't really talking to that extent, just getting rid of the single-chip solution, and moving to something with individual opamps, caps, etc. I should have been more clear, I can see how that could have been taken the wrong way. Reply
  • johan851 - Monday, October 21, 2013 - link

    Having read a lot of that guy's stuff, I'd say he knows enough to be dangerously misleading. Yes, everything in that article is true, but he adds a heavy spin by leaving out quite a bit of important information. He tends to focus only on the point he wants to prove (like discrete is worse) before he writes the article, then goes about finding information to back his point up.

    The opamp used for headphone amplification here is designed to be an output stage, and has built in output buffers. Typically opamps won't have this, as they're not optimized for use as an output stage and don't do a good job of current delivery into demanding loads. Headphones usually aren't very demanding, so you'll still see designs out there with opamp output stages. They're typically inexpensive, simple, and sound fine given those constraints as long as the load isn't too demanding. nwavguy doesn't mention this limitation.

    This particular amplifier opamp is a monolithic amp solution, so it designed to be used as an output stage and has built in buffers. That's a good start. The 13ohm output impedance (according to the datasheet) is... not so great. It tells you that the amp is going to struggle to produce clean output in demanding situations (and again, headphones aren't typically super demanding). There are a lot of benefits to non-discrete designs, including those things mentioned in nwavguy's article, but he doesn't mention one other important metric opamps are optimized for: cost. The TPA6120 chip mentioned here is a $5 part. That's not good or bad in itself, but it tells you what that this USB DAC is also optimized for cost. To some extent you get what you pay for, and I would say that this output stage is a *great* deal at $5. It's a very simple solution that'll sound better than anything you could build to replace it for up to $20 or so.

    Then you see the price tag of the DAC, and it makes you wonder where that $400 MSRP is going. :) I think that's what extide is getting at; the MSRP of this product, for what you're getting, is ridiculous. For $400, I would expect more than a $5 output stage. Replacing that output opamp with a discrete output stage (and opamps as the gain stage would still be good choice in this situation) would have the following tradeoffs:
    - higher cost
    - larger parts (good output transistors are necessarily large)
    - much better output impedance, meaning better current driving ability
    - more complex circuit design

    I would expect a $400 product to make those tradeoffs for quality rather than opting for the very inexpensive, simple single-chip design they did.
  • johan851 - Monday, October 21, 2013 - link

    Correction - that blog post does mention that opamps aren't good at driving difficult loads. Reply
  • AnnonymousCoward - Saturday, October 26, 2013 - link

    You guys are hilarious, and talk as if you designed the TPA6120 yourselves. Are you analog IC designers? If not, shut up.

    > The TPA6120 chip mentioned here is a $5 part.
    Too bad it costs $2.15 for 1000.

    > The 13ohm output impedance...tells you that the amp is going to struggle to produce clean output in demanding situations
    What's your basis? Don't you think the IC designers could have picked whatever they wanted, and they optimized it? SNR exceeds 120dB, there's 0.00014% THD+N, and output noise of just 5uV at 2V/V. But in your simple mind, a 13 ohm driver means it "struggles".
  • n00by - Monday, October 21, 2013 - link

    The fact that this soundcard/audio interface doesn't have balanced line-out for speakers/monitors kinda kills it for me. Not that I was looking to buy it, but if I ever were to replace my current audio interface then it could've been a candidate because most don't look very nice. Reply
  • Ganesh72 - Monday, December 16, 2013 - link

    I had this DAC for a couple of days. The main issue is that when listen to music via headphones , first 2 seconds of each track is missing; there are 2 seconds of noise and crack sound instead of music. It doesn't matter if I usd laptop via USB, or Blu Ray via coaxial the same issue. This makes IMPOSSIBLE to use ASUS Xonar STU as a headphone amplifier. Reply

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