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Post by PapaJac on Nov 27, 2012 12:26:26 GMT -5
USB audio is a popular, yet somewhat complicated, subject - and it is still evolving. Some DACs require drivers while others don't. Most computers can play 16/44 audio without any problems, but many, even some quite powerful ones, have problems playing higher-resolution files without dropouts and other issues. There are all sorts of choices and options, but the right ones aren't always obvious, and some combinations and options are still works-in-progress. In this thread we're going to try to cover three different things: 1) General information about USB audio - how it works and the state of the art. 2) Specific information about the USB input options on various Emotiva DACs, which ones require drivers on which computers, and how to configure your computer to get the best performance from your Emotiva DAC. 3) Advice and suggestions about what hardware to choose, and how to set it up, to create a dedicated computer-based audio system. Even though I've titled this thread "USB Audio", other types of computer connections (like optical and coax) are also fair game..... as long as one end is connected to a computer. Likewise, discussion of connecting a computer to a pre/pro is also welcome here. I think its time for Emotiva to take full advantage of these posts and develop the "Music Server" that might resolve all our digital music dilemmas. emotivalounge.proboards.com/index.cgi?action=display&board=updates&thread=25877&page=1#436797 Read LCSeminole post. "Music Server � Big Dan is a believer that streaming is the way of the future, and a Music Server is in the works. Two prototypes were in the lab. Lonnie mentioned the platform has the ability to find all computers/hard drives shared on the network to location music data, and Emotiva will add it�s audio �back end� onto this existing system. For now, it would only do 2-channel. No detailed on features/timing/price were available."
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Post by mrsinister on Nov 27, 2012 15:44:14 GMT -5
What I would be interested to know is where HDMI fits into all of this.
My current system: Desktop, Nvidia 560Ti --with HDMI run to Yamaha RX-A3000 VLC (as music software) No sound card
Being that this is audio straight from Video Card to Receiver, am I ok not having a sound card/DAC? or would I benefit? I dont see this discussed too often, and having a fancy sound card does me no good if it cant provide connections to lossless DTS-HD and its Dolby variant.
Thanks!
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Post by garbulky on Nov 27, 2012 15:57:29 GMT -5
What I would be interested to know is where HDMI fits into all of this. My current system: Desktop, Nvidia 560Ti --with HDMI run to Yamaha RX-A3000 VLC (as music software) No sound card Being that this is audio straight from Video Card to Receiver, am I ok not having a sound card/DAC? or would I benefit? I dont see this discussed too often, and having a fancy sound card does me no good if it cant provide connections to lossless DTS-HD and its Dolby variant. Thanks! You don't need a soundcard if you go HDMI. DACS usually don't process blu-ray surround sound or any kind of surround sound. They are usually two channel only. On average, a standalone DAC of a similar price has better quality than a reciever as more money is dedicated towards the production of sound vs features and amps. A reciever tends to be an exercise in compromise as it tries to do all things. However you have an expensive reciever so the only person that can tell you if you will notice a difference is you. You may be better off with a dedicated surround sound processor like the XMC-1 fed into one of emotiva's power amps. If your reciever has analog inputs you can take the digital input of a DAC into the reciever itself however the analog line stage and any processing the reciever does may affect the sound depending on the kind of receiver it is.
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KeithL
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Post by KeithL on Nov 27, 2012 23:35:30 GMT -5
Unfortunately, jitter is rather tricky to measure directly - and doing so requires some rather specialized (and expensive) equipment at the moment. When you see those graphs showing a big spike with little mountains around it, what you're seeing is a spectrum display of the output of a DAC. We feed in a pure tone, and what comes out should be a single vertical line - which is what the spectrum of a single pure tone looks like. The extra little spikes, and the spreading at the base of the line, are extra stuff that shouldn't be there. If we were to do that graph using an input with no jitter, we would see only the extra noise and distortion generated in the DAC itself. If we then send in an input signal with jitter, any EXTRA spikes and junk caused by the jitter will show up as EXTRA little spikes, a higher noise floor, and more spreading of the peak at the base. (To slightly oversimplify, each of those indicates a certain type of jitter.) The famous "J-test" used by the AP analyzer is actually somewhat less precise. Since precise amounts of jitter are hard to generate, J-test sends a sort of "torture track" signal to the device being tested - which causes the input circuitry to generate jitter - and we then look at the output. The problem is that we don't know how much jitter is being generated since THAT depends on the input circuitry. (It's sort of like measuring how well built a car is AND how quiet it rides by putting it on a paint shaker and measuring how much it rattles. You know that less rattles mean it's better built and/or quieter, but the details are not especially precise.) Jitter can be generated at the DAC, at the source (the biggest place for USB), and anywhere along the way. Cables don't really "make" jitter, but they can contribute to it. What happens is that the square waves get rounded off in the cable, and noise can get in as well. Either or both of those then make it harder for the input circuitry to "see" the edge of the square wave clearly, so it gets the exact transition point slightly wrong. The GOOD thing about jitter is that it ONLY counts at the DAC when the digital audio is converted to analog. If you had an analog preamp that created distortion, you could avoid adding more distortion by getting a better power amp, but you couldn't remove what was already there. What you got would be the sum total of all the distortions from all the components along the way. In contrast, small timing errors that accumulate along the digital path don't count at all as long as you correct them before doing the D/A conversion. The ASRC in the XDA-2 corrects the clock right before the DAC so, at least in theory, any and all jitter, regardless of where it came from, is removed. In practice, the ASRC reduces the jitter by a factor of hundreds or even thousands (depending on precisely what type of jitter it is), which is pretty darned close to removing all of it . This means that, in principle, there's no point in trying to reduce the jitter going in (beyond making sure it isn't so bad that the data is actually altered), and most differences between cables and sources in general should be largely eliminated when the ASRC is on. Incidentally, the XDA-2 itself doesn't re-sample before converting. However, the ASRC in the XDA-2 also re-samples to 96k as part of its operation to remove jitter. Because of this, engaging the ASRC produces a (very) slight difference in sound character beyond that caused by the elimination of jitter. I just wanna say thanks to Keith for starting this thread and for his posts here and in general as they're always very helpful! +1 Great series Keith, Thanks! Good to have all the info and comments in one place, and well timed with the release of the XDA-2. Is there any way to know, other than your ears, how much jitter is being 'delivered' by your connection of choice? Could vendors add a 'JitOmeter' to a DAC, or would you need clock info? What are the most likely places for jitter to be introduced into the signal, the cable?
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Post by garbulky on Nov 27, 2012 23:49:14 GMT -5
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KeithL
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Post by KeithL on Nov 27, 2012 23:50:30 GMT -5
At the moment, computer AUDIO and home theater are two different beasts. Virtually all audiophile DACs are limited to stereo, and decoding surround sound is generally left to pre / pros with lots more processing power and configuration options. The XDA-2 (and pretty well all other audiophile stereo DACs) ONLY plays two-channel PCM stereo digital audio. When using a USB DAC, there is no point whatsoever in having a sound card (the USB DAC is "a USB sound card" already). If you preferred to use Toslink or S/PDIF, then you could add a sound card with those outputs (because most computers' internal sound cards don't have them). Because of the way a computer handles video and audio, some computer video cards can send audio through the HDMI connection along with the video and others cannot (many ATI cards can, most others can't). This is often limited to sending the audio along with the video when playing a DVD or Blu-Ray disc. (In principle it would be possible to play an audio file and send it along the HDMI connection to a pre-pro, but it would require cooperation from the video card, the player program, and the drivers in the computer. There are probably ways of doing it, but I don't know of any offhand.) There are also low-cost computer "USB sound cards" that provide a Toslink digital output, which can be configured to pass surround sound to the digital input on a pre / pro, and there are obviously sound cards that do include surround decoding and provide 7.1 channel analog outputs directly. (They would, however, be irrelevant to playing stereo audio through the XDA-2.) What I would be interested to know is where HDMI fits into all of this. My current system: Desktop, Nvidia 560Ti --with HDMI run to Yamaha RX-A3000 VLC (as music software) No sound card Being that this is audio straight from Video Card to Receiver, am I ok not having a sound card/DAC? or would I benefit? I dont see this discussed too often, and having a fancy sound card does me no good if it cant provide connections to lossless DTS-HD and its Dolby variant. Thanks!
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KeithL
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Post by KeithL on Nov 27, 2012 23:59:44 GMT -5
Yes, thanks. The USB hardware in the XDA-2 (and the rest of the hardware) is quite stable. We have occasionally seen cases where a particular USB port simply doesn't seem to work well with the input circuitry on the XDA-2. On the few occasions we've seen this so far, simply moving the XDA-2 to a different USB port on the computer or using a different cable usually eliminates the issue. This sort of problem can also be caused by conflicts with drivers and/or configuration issues with the player program. Apple computers DO use USB Audio Class 2 drivers to talk to the XDA-2 - but, with Apple, the drivers are already part of the O/S (which is why you don't have to install them). Unfortunately, it also means we don't have much control over that side of things. As a last resort, it might be easier to switch to the Toslink optical port (which most modern Apples also have) rather than try to troubleshoot the driver issue.
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Deleted
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Post by Deleted on Nov 28, 2012 19:21:20 GMT -5
I will be the first to admit that I have little knowledge about DAC's. But why is it that DAC's only have USB, Coax, or Optical options? With all the computers that are out now with HDMI you would think that there would be DAC's with an HDMI port. I bought an ASUS net book solely for the purpose of streaming music and movies. It works great! When I get an Oppo BDP-103 I am hoping to be able to go from HDMI out on the Asus to the HDMI in on the Oppo to take advantage of the Oppo's DAC. Is there anything wrong with this scenario? Will this even work?
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Post by garbulky on Nov 28, 2012 19:56:17 GMT -5
I will be the first to admit that I have little knowledge about DAC's. But why is it that DAC's only have USB, Coax, or Optical options? With all the computers that are out now with HDMI you would think that there would be DAC's with an HDMI port. I bought an ASUS net book solely for the purpose of streaming music and movies. It works great! When I get an Oppo BDP-103 I am hoping to be able to go from HDMI out on the Asus to the HDMI in on the Oppo to take advantage of the Oppo's DAC. Is there anything wrong with this scenario? Will this even work? There are very few DACS that have HDMI input. HDMI requires a fee and I suspect that's why you don't see it on DACs. I too would like to see HDMI input and possibly passthrough. It just makes sense with everything having HDMI outputs. What would be even neater is the possibility for DACS to have onboard decoding of blu-ray and SACD audio into two channel.
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Deleted
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Post by Deleted on Nov 28, 2012 22:29:23 GMT -5
That would be really cool. I believe it will get there before long. That's why I don't want to spend a lot for a DAC right now. Things are just changing too fast. Do you think computers with HDMI outs would benefit much soundwise and/or videowise from accessing the DAC's/Qdeo chip in the new Oppo's thru their HDMI ins? I've not read any comments about anyone that has tried that.
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Post by savjac on Nov 28, 2012 23:01:41 GMT -5
One thing I might mention is that when using USB several problems can and do occur. Using a Mac, if you look at the USB tree you may find that there is a circuit before the USB port that not only powers USB but the keyboard for instance. This could interrupt the signal during playback if the keyboard powers on and off. Second, Windows USB is set up to use a certain percentage of the power for the power supply. Some USB connections can use say 10% of a given about allotted to all of the USB slots in your computer. Others can use 20% of the alloted power or more. Watch for the one with the least other goodies in line with the USB slot as well as use the ones with the most power allotted. Now, the USB connection and cable itself will use very little power and if running longer lengths over 15' please be sure to use a USB repeater cable. This stuff gets so confusing. Yes, thanks. The USB hardware in the XDA-2 (and the rest of the hardware) is quite stable. We have occasionally seen cases where a particular USB port simply doesn't seem to work well with the input circuitry on the XDA-2. On the few occasions we've seen this so far, simply moving the XDA-2 to a different USB port on the computer or using a different cable usually eliminates the issue. This sort of problem can also be caused by conflicts with drivers and/or configuration issues with the player program. Apple computers DO use USB Audio Class 2 drivers to talk to the XDA-2 - but, with Apple, the drivers are already part of the O/S (which is why you don't have to install them). Unfortunately, it also means we don't have much control over that side of things. As a last resort, it might be easier to switch to the Toslink optical port (which most modern Apples also have) rather than try to troubleshoot the driver issue.
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KeithL
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Post by KeithL on Dec 1, 2012 17:15:13 GMT -5
It looks like you should be able to do that - and it should work fine. The only requirement is that your Asus puts out audio on the HDMI output (some PCs do, but many do not, and so require a separate audio connection). In that case, the Oppo would also be serving as "an HDMI DAC"... which is what pre / pros are anyway..... Don't be confused by the terminology (which can be confusing). Take our new UMC-200, which is a pre / pro will full audio processing and fast video switching (but no video processing per-se), put tape over the HDMI video output, and you have an HDMI DAC. I will be the first to admit that I have little knowledge about DAC's. But why is it that DAC's only have USB, Coax, or Optical options? With all the computers that are out now with HDMI you would think that there would be DAC's with an HDMI port. I bought an ASUS net book solely for the purpose of streaming music and movies. It works great! When I get an Oppo BDP-103 I am hoping to be able to go from HDMI out on the Asus to the HDMI in on the Oppo to take advantage of the Oppo's DAC. Is there anything wrong with this scenario? Will this even work? There are very few DACS that have HDMI input. HDMI requires a fee and I suspect that's why you don't see it on DACs. I too would like to see HDMI input and possibly passthrough. It just makes sense with everything having HDMI outputs. What would be even neater is the possibility for DACS to have onboard decoding of blu-ray and SACD audio into two channel.
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KeithL
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Post by KeithL on Dec 1, 2012 17:15:35 GMT -5
It looks like you should be able to do that - and it should work fine. The only requirement is that your Asus puts out audio on the HDMI output (some PCs do, but many do not, and so require a separate audio connection). In that case, the Oppo would also be serving as "an HDMI DAC"... which is what pre / pros are anyway..... Don't be confused by the terminology (which can be confusing). Take our new UMC-200, which is a pre / pro will full audio processing and fast video switching (but no video processing per-se), put tape over the HDMI video output, and you have an HDMI DAC. I will be the first to admit that I have little knowledge about DAC's. But why is it that DAC's only have USB, Coax, or Optical options? With all the computers that are out now with HDMI you would think that there would be DAC's with an HDMI port. I bought an ASUS net book solely for the purpose of streaming music and movies. It works great! When I get an Oppo BDP-103 I am hoping to be able to go from HDMI out on the Asus to the HDMI in on the Oppo to take advantage of the Oppo's DAC. Is there anything wrong with this scenario? Will this even work? There are very few DACS that have HDMI input. HDMI requires a fee and I suspect that's why you don't see it on DACs. I too would like to see HDMI input and possibly passthrough. It just makes sense with everything having HDMI outputs. What would be even neater is the possibility for DACS to have onboard decoding of blu-ray and SACD audio into two channel.
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KeithL
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Post by KeithL on Dec 1, 2012 17:31:05 GMT -5
I wanted to address this part of the question separately. You will NEVER see the last part of that (at least not until the licensing changes) because both Blu-Ray and SACD licensing only allows three options: 1) decode the digital audio and send it out as analog audio 2) send out the digital audio (still encoded) to some other device 3) send out a reduced-quality version of the digital audio in some other form The "DAC" you're talking about is a preamp / processor.... it decodes the audio, puts it out as analog audio, and passes the HDMI video on to the TV. Most pre / pros CAN send out a mixed-down version in digital form, but the quality will be limited (usually to 24/48) for reasons of copy protection - as required by the licenses.. There are very few DACS that have HDMI input. HDMI requires a fee and I suspect that's why you don't see it on DACs. I too would like to see HDMI input and possibly passthrough. It just makes sense with everything having HDMI outputs. What would be even neater is the possibility for DACS to have onboard decoding of blu-ray and SACD audio into two channel. [/quote]
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Deleted
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Post by Deleted on Dec 3, 2012 1:11:07 GMT -5
My Asus does output audio & video thru it's HDMI out. Just to make sure I understand you are you saying that because of copyright protection you get approximately 24/48 through HDMI out of a computer to the Oppo's HDMI in, or a pre/pro's HDMI in, whereas with a USB/Coax/Optical DAC 24/192 is achievable?
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Post by redbeemer on Dec 5, 2012 17:10:55 GMT -5
My Asus does output audio & video thru it's HDMI out. Just to make sure I understand you are you saying that because of copyright protection you get approximately 24/48 through HDMI out of a computer to the Oppo's HDMI in, or a pre/pro's HDMI in, whereas with a USB/Coax/Optical DAC 24/192 is achievable? I don't believe that is correct. My Acer laptop as well as my HP desktop before it outputs the full resolution of my HD audio files(up to 96/24) using JRiver Media Center via HDMI output. If HDMI output were limited to 24/48, then you could never play DTS-HD Master or Dolby TrueHD audio out when playing a Blu-ray disc. I specifically use HDMI output from my computer to my Denon 4311 AVR since that way I am assured of getting the full resolution of my audio files to the onboard DAC in the AVR. I hope this helps.
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KeithL
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Post by KeithL on Dec 6, 2012 15:49:42 GMT -5
Not exactly. HDMI is considered to be a "secure link" between devices (for reasons of security and preventing piracy) - it is even actually encrypted to prevent the signal being "intercepted". An HDMI device may receive input via HDMI, and send output via HDMI, at any resolution it likes. For example, a converter can take in component video at full HD and output HDMI at full HD (because we are going from "unsecured" to "secured"). HOWEVER, a converter cannot take in full HD video via HDMI and send it out via component video (because we are going from "secured" to unsecured"). The reason is that doing so would expose the secured HD video signal to being copied, and so "break" the HDMI security. I believe that the default minimum security in HDMI itself would allow you to output the video at reduced resolution, but Blu-Ray discs in specific have the option of "requesting" different levels of security, and, for many, that means no output at all. This continues to change - you can Google "HDCP" for the latest and greatest details. There are similar restrictions on audio. As far as I know, "legal" devices with HDMI inputs are restricted to putting out audio at 24/48 or below. SACDs have their own security requirements; a SACD player can send digital audio from a SACD through HDMI (because it is "secure"), but cannot send it out as other forms of high-resolution digital audio. DVD-A has similar restrictions for the same reason. The simplest way to remember it is that there are no digital recorders that accept HDMI inputs, and no HDMI or SACD device will let you have full quality digital output in any format that you CAN feed into a recorder (so no SPDIF coax or optical). You get either reduced resolution or silence..... Now this is all for "devices" like the Oppo or another standalone player. Computer players and cards are supposed to follow similar rules, but some may simply fail to follow the rules. Likewise, some computer hardware may not even do everything it's allowed to. An example there is audio over HDMI... On most computers, the HDMI output comes from the graphics card. This is NOT the same as the HDMI from a Blu-Ray player... the computer actually "handles" the video and audio separately. Therefore, it becomes a matter of whether the computer is willing to properly recombine them to send them out the HDMI output. Some graphics cards simply don't handle audio - period; in which case you will need an extra connection for the audio. Some actually take the audio output as a separate output, and then plug it back into the video card and recombine it with the video. The point is that, when you play a Blu-Ray on a computer, it has been "disassembled and reassembled", so the audio options available will be as much determined by what the computer and your player software support as by what was recorded on the original disc. For example, depending on your sound card and graphics card, you might play a dolby digital surround disc and end up with stereo PCM sound coming out of your HDMI port. My Asus does output audio & video thru it's HDMI out. Just to make sure I understand you are you saying that because of copyright protection you get approximately 24/48 through HDMI out of a computer to the Oppo's HDMI in, or a pre/pro's HDMI in, whereas with a USB/Coax/Optical DAC 24/192 is achievable?
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bibo
Seeker Of Truth
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Post by bibo on Dec 12, 2012 3:11:21 GMT -5
Hello and welcome, yesterday my XDA-2 arrived:) Did anybody now if there is any chance to let it work with USB and a Squeezebox touch with "Triodes Enhanced Digital Output app" Thanks
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Post by GreenKiwi on Dec 12, 2012 3:34:23 GMT -5
I'm guessing there is a reasonable chance that it works
That being said their class 2 driver would have to work... but follow all the steps in that link and give it a try. Very cool.
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bibo
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Post by bibo on Dec 12, 2012 14:22:48 GMT -5
Hello
thanks for your help, but after several hours of frustration I decided to take the Coaxial Inputs... If anybody can handle it please feel free to tell me...
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