USB Audio and Computer Audio

[KeithL]

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.

[audiofile]

One thing I have learned when researching DACs and their capabilities, specifically bit depth and sample rate, is that USB audio is usually rated lower than other inputs, such as Toslink or digital coax. Very few DACs will process USB audio at a 24 bit / 192 kHz rate.

Interestingly enough, the Emotiva DACs (XDA-1 & XDA-2) support 24 bit / 192 kHz rates on all inputs.

Your computer holds the drivers for the USB device. The source of your file is also critical. Understanding the differences between file types is paramount to realizing a high quality audio experience vs. another iPod experience. Uncompressed, lossless files such as FLAC are my first choice.

Since I use a home server, a key component for digital music input to my DAC is the quality of the sound card installed. Obviously, the card output should be of the highest quality and highest bit depth / sampling rate available.

As fast as technology changes, a specific hardware suggestion today becomes outdated tomorrow...if not by the end of the work day today! But, for that moment in time you are shopping for hardware, try to be consistent with the specifications between components you are going to purchase.

[maximumkahuna]

"Interestingly enough, the Emotiva DACs (XDA-1 & XDA-2) support 24 bit / 192 kHz rates on all inputs."

Not true. The XDA-1 usb input is limited to 16/44.1. However it does 24/192 on the coax input. So if you get a used XDA-1 and a decent spdif converter you can have a dynamite usb dac for under $300. The XDA-2 does do hirez usb directly.

[jackfish]

Nov 26, 2012 13:33:48 GMT -5 maximumkahuna said:

"Interestingly enough, the Emotiva DACs (XDA-1 & XDA-2) support 24 bit / 192 kHz rates on all inputs."

Not true. The XDA-1 usb input is limited to 16/44.1. However it does 24/192 on the coax input. So if you get a used XDA-1 and a decent spdif converter you can have a dynamite usb dac for under $300. The XDA-2 does do hirez usb directly.

Actually the XDA-1 will do 24 bit, 48 kHz in USB.

[copperband]

"However it does 24/192 on the coax input"

Does the XDA-1's "optical" input does 24/1492 too?

[jackfish]

My experience with computer audio is limited to what I ended up with. I wanted something portable, so I got a MacBook Air. I currently have 220 GB of lossless music on the 256 GB SSD drive, which is backed up to a 2TB USB drive. Since the MacBook Air has no coax or optical digital output I was resigned to a USB interface. In looking at a USB DAC under $500 my research led me to the Schiit Bifrost USB DAC. It was just one of many ways to get into computer audio, but for me it was a very easy way, and has exceeded my expectations.

[Dark Ranger]

Nov 26, 2012 14:09:44 GMT -5 copperband said:

Does the XDA-1's "optical" input does 24/1492 too?

Yes, the optical inputs support up to and including 24/192.

[KeithL]

Actually the XDA-1 does up to 24/192 on the coax and Toslink inputs.

While the XDA-1 itself can accept 24/192 over Toslink, many transmitters only go up to 24/96 (and some Toslink cables are similarly limited). Whether you actually GET 24/192 to work will therefore depend on the transmitter in your source equipment and your cable. Coax ALWAYS works at up to 24/192 and so is preferable.

Nov 26, 2012 14:09:44 GMT -5 copperband said:

"However it does 24/192 on the coax input"

Does the XDA-1's "optical" input does 24/1492 too?

[audiofile]

Nov 26, 2012 14:31:38 GMT -5 KeithL said:

Actually the XDA-1 does up to 24/192 on the coax and Toslink inputs.

While the XDA-1 itself can accept 24/192 over Toslink, many transmitters only go up to 24/96 (and some Toslink cables are similarly limited). Whether you actually GET 24/192 to work will therefore depend on the transmitter in your source equipment and your cable. Coax ALWAYS works at up to 24/192 and so is preferable.

So cable and source generator need also be examined, eh? Good info!

I'll have to dig up my XDA-1 spec sheet again because I swore Vincent told me 24/192 for ALL inputs. Then again, I don't use USB for music on my XDA-1 so it's a moot point for me.

[KeithL]

There are several reasons why "USB is usually rated lower" than other types of inputs - and not all of them are (still) true.

In the old days, very few USB inputs supported 24/192; today many do. Depending on who you ask, this is or is not important. (There isn't very much music available at 192k, many people never hear a difference between 96k and 192k at all, and a lot of the music that IS now available at 192k came from masters that aren't good enough that it matters.)

Another issue is jitter. In the old days, most USB outputs had HUGE amounts of jitter (enough that they sounded noticeably bad) and most S/PDIF inputs had lower jitter. However, modern USB inputs have much less jitter to begin with, and we have various very effective methods of controlling or removing jitter (like the XDA-2's sample rate converter), so this isn't as much of an issue.

With a USB connection, you don't actually need a sound card at all (if you're playing files). With S/PDIF, you need a sound card that supports S/PDIF output at the sample rates and bit depths you want to play, but it still doesn't make much difference to buy a much more expensive one beyond that point. Fancy sound cards usually have better DACs and audio sections in them - which you won't be using anyway.

In either case, your machine needs to be fast enough, and configured well enough, that it doesn't drop data or otherwise just plain screw up but, improving things beyond that point doesn't buy you much. Some machines do work better with a particular sound card or software, but don't automatically assume that it will make a huge difference.

Nov 26, 2012 13:23:31 GMT -5 audiofile said:

One thing I have learned when researching DACs and their capabilities, specifically bit depth and sample rate, is that USB audio is usually rated lower than other inputs, such as Toslink or digital coax. Very few DACs will process USB audio at a 24 bit / 192 kHz rate.

Interestingly enough, the Emotiva DACs (XDA-1 & XDA-2) support 24 bit / 192 kHz rates on all inputs.

Your computer holds the drivers for the USB device. The source of your file is also critical. Understanding the differences between file types is paramount to realizing a high quality audio experience vs. another iPod experience. Uncompressed, lossless files such as FLAC are my first choice.

Since I use a home server, a key component for digital music input to my DAC is the quality of the sound card installed. Obviously, the card output should be of the highest quality and highest bit depth / sampling rate available.

As fast as technology changes, a specific hardware suggestion today becomes outdated tomorrow...if not by the end of the work day today! But, for that moment in time you are shopping for hardware, try to be consistent with the specifications between components you are going to purchase.

[KeithL]

As for 24/192 over Toslink.... a significant number of devices simply can't do it - and it is rarely explicitly rated one way or the other. You should always start with the shortest cable possible, be careful to avoid sharp bends or kinks (they actually cut down on the light transfer above and beyond risking an outright break), and make sure the ends are nice and clean. Most Toslink cables are plastic core, but there are more expensive glass-fiber ones available; they do transmit more light, but I don't know if it would actually help in real life or not (it would probably help if you have a situation where you get 24/192 for one or two feet but it stops working for longer cables).

Windows often (for some reason) seems to be unwilling to let you choose 48k with the XDA-1, and so limits you to 44k.The XDA-1 USB input hardware is limited by the receiver chip to 48 kbps sample rate.

Depending on the version you use, and your player software, and the settings, Windows will often play files of higher sample rates - and simply convert them down on the fly (without telling you).

Nov 26, 2012 14:41:39 GMT -5 audiofile said:

Nov 26, 2012 14:31:38 GMT -5 KeithL said:

Actually the XDA-1 does up to 24/192 on the coax and Toslink inputs.

While the XDA-1 itself can accept 24/192 over Toslink, many transmitters only go up to 24/96 (and some Toslink cables are similarly limited). Whether you actually GET 24/192 to work will therefore depend on the transmitter in your source equipment and your cable. Coax ALWAYS works at up to 24/192 and so is preferable.

So cable and source generator need also be examined, eh? Good info!

I'll have to dig up my XDA-1 spec sheet again because I swore Vincent told me 24/192 for ALL inputs. Then again, I don't use USB for music on my XDA-1 so it's a moot point for me.

[KeithL]

As you probably know, the XDA-2 now displays the sample rate of the incoming digital audio on the display.

You may notice that the rate you see displayed is sometimes different than you expect. Specifically, you may see 44.1 displayed (or 96k) when you were expecting a higher sample rate.
THE SAMPLE RATE ON THE XDA-2 DISPLAY IS CORRECT. Many operating systems, including Windows, often re-sample the playback rate for digital audio files as they are played.

So, for example, you may play a 96k file in FooBar2000 (a very popular player program), and see 96k displayed in the player status window, but see 44.1 displayed on the XDA-2's display. What's happening is that FooBar2000 is playing your 96k file, and correctly reporting the sample rate. It then passes the file to Windows, which is re-sampling the file to 44.1k (which is probably set as its default rate), and passing it on to the XDA-2, which then correctly reports what IT receives as 44.1k.

Whether this happens or not will depend on your software (Windows 7 does it by default, as do some Macs). In some instances you may be able to choose a different playback mode which doesn't re-sample, some players may automatically override the Windows preference, and you may actually find that you prefer the sound of a specific sample rate (for example, some people prefer to let Windows up-sample their 44.1k files to 96k).

[The XDA-2 does have an ASRC (sample rate converter) which INTERNALLY re-samples data to 96k while eliminating jitter when it is engaged (NOT bypassed). The operation of the ASRC is transparent to the display; the display will always display the sample rate of the incoming data as it really is, even when the ASRC is operating.]

[monkumonku]

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!

[powxpa]

I really curious about usb audio. How do you play music from pc through usb cable? what programs do i need?

[Dark Ranger]

Nov 26, 2012 15:43:22 GMT -5 powxpa said:

I really curious about usb audio. How do you play music from pc through usb cable? what programs do i need?

There are several ways to do it. Two of the most common methods are explained below:


1) After connecting the USB DAC to your computer (and installing the driver if applicable), the DAC will show up in your available Audio Devices. You just select the USB DAC as the default playback device. Most applications (iTunes, Windows Media Player, etc.) will automatically send audio to the default playback device.

2) Some programs (like JRiver Media Center) allow you to select the output device without regard to system defaults. So as an example, you might have your computer HDMI output set for default audio output, but JRiver would allow you to use the SPDIF/optical output instead.


You don't need any specific programs to use USB-based audio devices. What you're using right now will work just fine. All that you need to do is configure the computer (or program) to use the USB DAC. Regarding USB cables, I recommend using a quality, shielded USB cable for best performance. There's no need to buy exotic and expensive USB cables, though. I use a Belkin gold series cable purchased for $10 on sale.

[garbulky]

Also powxpa, make sure you use a software player that provides bit-perfect audio for the best sound quality. J-river and the free foobar will do it using a technique called WASAPI for windows. YOu have to manually tell these players to use WASAPI. For instance foobar, you need to download a free WASAPI plugin and configure the output to be wasapi.

[AudioHTIT]

Nov 26, 2012 15:29:43 GMT -5 monkumonku said:

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?

[hemster]

I too want to add my vote of thanks to Keith for this thread. I hope it helps many and I know that I'm still (and continuously) learning about this stuff. There's a lot more to digital than 1s and 0s!

[bargain]

When streaming is going to be the focus of Emotiva products going forward, it's great to read a laymans terms thread on this, cheers

I'm sure if I did a bit of googling it would have become clear, but I'd wondered for a while what the go was with 'usb audio' for hi-rez music...

It's good to know that it basically just 'becomes' your sound card when you plug it in. Awesome! Good reason to get some newer better headphones as well (referring to the XDA-2 of course)

[savjac]

I have been playing with computer audio for some time now and can say first hand that J River Media center is much better than Windows is at playing your music files. By better I mean sound and delivery to your external DAC. I also use a Music Fidelity V-Link 192 to change the USB to SPDIF and stop and jitter issues. This are sounding very good this way.