USB Audio and Computer Audio

[Loop 7]

Feb 1, 2015 17:16:11 GMT -5 audiobill said:

CDs are so 2000's.

I agree about CDs now that my Mini with a USB DAC, Amarra and iTunes actually sounds better than discs. I'm guessing locally stored audio will end in the next decade.

[audiobill]

Apr 23, 2015 17:19:58 GMT -5 Loop 7 said:

Feb 1, 2015 17:16:11 GMT -5 audiobill said:

CDs are so 2000's.

I agree about CDs now that my Mini with a USB DAC, Amarra and iTunes actually sounds better than discs. I'm guessing locally stored audio will end in the next decade.

Now, add Tidal and you'll really be singing!

[charlieeco]

Nov 26, 2012 12:39:37 GMT -5 KeithL said:

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.

[charlieeco]

So clear, music server connected via HDMI to OPPO BD-103 then OPPO analog outputs to UMC-200 (analog inputs) would sound with limitations in quality??
will it happen the same if Music server via HDMI is connected to HDMI inputs in the <UMC-200

[garbulky]

If you don't have subwoofer management turned on, I don't think there would be a limitation in sound quality. Basically if you do it usig the analog outputs of oppo then you will use the DACs of the Oppo. This is the thing that converts digital 1's and 0's to an actual analog music signal that will move your speakers. It's where the "quality" comes from.

If you go HDMI to UMC-200 HDMI input then you will be using the DAC of the UMC-200. One of them may be better than the other but I can't tell you which one.
If you use the oppo analog outputs and have subwoofer in your UMC-200 system with bass management, then the UMC-200 will take the analog output of the oppo and then reconvert it back into digital 1's and 0's. Then after it does that, it will then use its own DAC to convert the digital 1 and zero BACK to the analog music signal. So here you are oging from D to A, and then A back to Digital and then Digital to analog. (Obviously, you may want to avoid that).

[charlieeco]

Thanks a lot for explanation, so it will be better to conect the Music server with all my FLAC files via HDMI directly to EMO UMC-200, Does anyone have a comparision of tech specs on both DACS (the OPPO 103D and the UMC-200), maybe KeithL can help us in that particular issue.
Thanks again

[charlieeco]

Think it would be better to avoid the conection via USB, wwhen you have HDMI available from your computer, do you think so?

[rcheliguy]

Asynchronous USB has more bandwidth than HDMI does.

I'm currently using
JRemote - iPad ( nice slick and feels like instant response )
JRiver Media Center - PC
Asynchronous USB to OPPO 105D using the OPPO driver.

I've run 96kHz x 24bit uncompressed audio without any issues.

I play everything using JRiver now.

[jmilton]

^ HDMI allows up to 8 channels of uncompressed audio at sample sizes of 16-bit, 20-bit and 24-bit, with sample rates of 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz and 192 kHz
.
HDMI 2.0 = up to 32 channels of audio, up to 1536 kHz audio. How does USB have more bandwidth?

[rcheliguy]

I stand corrected. I just looked it up and got this.

HDMI = 5.1 x 192kHz or 7.1 x 96kHz

USB Audio = 2ch 192kHz

Coax Audio = 2ch x 96kHz

And that is just what the OPPO 105D supports not the official specification for them.

[dudeisms7]

HDMI vs USB comes down to jitter... and whether or not your ears can even perceive it.... and how your device acting as the dac handles jitter or clocks the data.  Many folks seem to like using Oppo's as their DAC, perhaps it may sound better as a DAC rather than the UMC-200.  If you pass the audio via Hdmi the UMC-200 will act as the DAC.  Try it both ways, see what is most pleasing to your ears.

[rcheliguy]

May 22, 2015 11:03:02 GMT -5 dudeisms7 said:

HDMI vs USB comes down to jitter... and whether or not your ears can even perceive it.... and how your device acting as the dac handles jitter or clocks the data.  Many folks seem to like using Oppo's as their DAC, perhaps it may sound better as a DAC rather than the UMC-200.  If you pass the audio via Hdmi the UMC-200 will act as the DAC.  Try it both ways, see what is most pleasing to your ears.

I really wonder how much of an issue jitter really is with any asynchronous protocol.

If the music data is sent by Ethernet, WiFi or USB the bits are 100% verified and buffered so the DAC is reading the data with its own clock rate and no one else's.

The Asyncronous USB, WiFi, Ethernet is just doing the equivalent of a file transfer.  All the data is verified and delivered to the DAC's buffer intact. It sends a chunk of "music data" over until the buffer is full and than waits until there is room to send more bytes.

There should be no way for clock boundaries to have any impact on the music data or how the DAC reads that data. 

If the data didn't reach the DAC intact it would mean that proven data transport layers don't work and we know that they do.

[dudeisms7]

USB connections use a one way digital connection for music replay and use the computer's bus frame rate as source for the clock which is less stable than a fixed one. A computer sadly cannot maintain perfect timing of the data sent via USB. A computer's clock is not as stable (powerline fluctuations/RF pollution) as you would like for highend audio purposes. Digital audio streaming is a "real-time" process, meaning that the actual timing of the transfer of each data bit from the source to the D/A converter is important and must be as precise as possible. Data transfers to disk or a printer are not real-time because there is no urgency for the data to arrive at the printer or disk to prevent errors from happening. The data arrives whenever it does and then the device does its job with the data, either writing it to the disk or storing it in a print buffer. If the data does not arrive in time to be written on a particular sector of a disk, the hardware just waits for the disk to rotate again. Streaming audio data on the other hand must arrive at precise time intervals in order that the D/A device create an accurate representation of the original recording. If it does not "keep-up" the pace, then dropouts will occur and the D/A converter will fall out of sync. The clock that moves the data into the D/A cannot be missing any "ticks" and each tick must be precisely placed in time. The audio data transfer must include both 1) accurate data and 2) accurate timing, whereas non-real-time transfers only require accurate data.

Networked audio (Ethernet), both wired and WiFi is a unique case. Because the data is transmitted in packets with flow-control, re-try for errors and buffering at the end-point device, it is not as much of a real-time transfer as USB, S/PDIF or Firewire. The computer transmitting the data packets must still keep-up" the pace to prevent dropouts from occurring, but the real-time nature of the transfer is looser. Unlike with other protocols, there can be dead-times when no data is being transferred. Networking also avoids the use of the audio stack of the computer audio system since it treats all data essentially the same. Because of the packet-transfer protocol of Ethernet and data buffering at the end-point, the jitter of the clock in the computer is a non-issue. The only clock that is important is the one in the end-point device.... Like a dac, network player, or streamer. This would seem to be the ideal situation, which it certainly is. The only problem that can occur is overloading the network with traffic or WiFi interference, which may cause occasional dropouts. The problem for audiophiles is that the majority of these end-point devices were designed with high-volume manufacturing and low-cost as requirements, with performance taking a lower priority. As a result, the jitter from these devices is higher than it could be. It should be the lowest of all the audio source devices available...and it usually is if the device has a quality clock

[qdtjni]

You just described Sycnronous USB transfer, in most cases of USB DACs, Asyncronous USB is used, which uses the clock of the DAC so an unstable clock on the computer side is not affecting the transfer. FTR, USB is also packaged and use buffers.

Also, it is not the Ethernet packaging that is relevant for networked audio, it is the TCP protocol and in some instances UDP.

EDIT: corrected typos

[vneal]

I think you will get better results running your computer or external hard drive HDMI directly to your Oppo 103 using its internal DAC chip Vs directly to the Emotiva 200.7---------That has been my experience 

Computers fail. That is why I recommend a separate external hard drive for stored music files. I have worked with hundeds of computers and in time they will all fail  and I have yet to see an external hard drive fail

[rcheliguy]

May 24, 2015 5:47:09 GMT -5 vneal said:

I think you will get better results running your computer or external hard drive HDMI directly to your Oppo 103 using its internal DAC chip Vs directly to the Emotiva 200.7---------That has been my experience 

Computers fail. That is why I recommend a separate external hard drive for stored music files. I have worked with hundeds of computers and in time they will all fail  and I have yet to see an external hard drive fail

I completely agree with you about making back copies of your music!  

I have mine backed up to a 3Tb drive and a large thumbdrive.

I found a description of the different types of USB Audio transfer.


USB AUDIO - SYNCHRONOUS/ASYNCHRONOUS DATA TRANSFER



There are a couple of methods for sending audiodata over an usb cable. Here's an explanation of the principles behind them and the advantages of one over another.





Synchronous USB connections use a one way digital connection for music replay and are considered the worst type of connection for audio purposes

Adaptive mode is a little smarter. It asesses the amount of data in the frame and adjusts that dac's clock-timing to it.

Asynchronous mode is technically most advanced in that it has a feedback loop so that the amount of data in the frame can be controlled.



Conventional USB connections use a one way digital connection for music replay and use the computer's bus frame rate as source for the clock which is less stable than a fixed one. A computer sadly cannot maintain perfect timing of the data sent via USB. For adaptive mode, the receiving chip adapts to this drifting signal by re-adjusting its own frequency every milisecond to match the incoming frequency. This is already considered better. The downside of both methods is that they tend to cause high levels of jitter. On top of this, the computer's clock is not as stable (powerline fluctuations/RF pollution) as you would like for highend audio purposes.



Asynchronous USB (not to be confused with asynchronous samplerate conversion) uses a clock housed near the dac (usually in the external dac's casing) and allows it to drive the converter directly, thereby not relying on the instable computer's clock. Well, someone who is technically more adept at this matter than me informed me that this is still not entirely true as the interface or dac is still somewhat dependent upon the stability of the PC's bus clock*. It is called asychronous because the dac's master clock isn't synchronized directly to any clocks within the computer. Instead, the dac is controlled by a (potentially high-precision) fixed-frequency clock. This clock controls the datastream from the computer to a buffer near the DA converter.

[charlieeco]

Wonderful technical explanation, thanks to all of you , I think i´ll try from music server to oppo 103D via HDMI.

[ksan]

I stream my iTunes lossless music from iMac through Monster USB cable to Emotiva Stealth DC-1, I get 24 bit 192K rate. I have yet to try Toslink but hearing from others that USB cable might give better tone than that from optical cable.

[Mark]

Hi All,
Glad to have a forum that I can consult with.   Thank you all for any help or advice.  Here is my streaming setup and issue:

Synology NAS running Logitech Media Server (upstairs)
Powerline Ethernet to downstairs, to
Sonic Orbiter SE (Cubox ARM) running SqueezeLite via
USB to
XDA2 to
RCA analog to my Integra Receiver

I have learned that when powering up the XDA, it takes 100 seconds for the USB bus to be recognized and ready to stream.  I found this out through a live debug session with the tech pros at Sonic Orbiter, they were able to connect to my SOSE and see the  DAC behavior and help debug the long connect time, as I thought the delay was on their end.  It's not.   One suggestion was to keep the XDA powered on.  I might if the power draw is sufficiently low.   Any insights into startup time for the USB DAC?  BTW, the SQ of this new setup is really good, kills the Squeezebos Duet it replaced...

Thanks for ideas and feedback,
Mark

[hemster]

Mar 4, 2016 19:06:24 GMT -5 Mark said:

Hi All,
Glad to have a forum that I can consult with.   Thank you all for any help or advice.  Here is my streaming setup and issue:

Synology NAS running Logitech Media Server (upstairs)
Powerline Ethernet to downstairs, to
Sonic Orbiter SE (Cubox ARM) running SqueezeLite via
USB to
XDA2 to
RCA analog to my Integra Receiver

I have learned that when powering up the XDA, it takes 100 seconds for the USB bus to be recognized and ready to stream.  I found this out through a live debug session with the tech pros at Sonic Orbiter, they were able to connect to my SOSE and see the  DAC behavior and help debug the long connect time, as I thought the delay was on their end.  It's not.   One suggestion was to keep the XDA powered on.  I might if the power draw is sufficiently low.   Any insights into startup time for the USB DAC?  BTW, the SQ of this new setup is really good, kills the Squeezebos Duet it replaced...

Thanks for ideas and feedback,
Mark

I'm not using USB with my XDA-2 but 100 seconds is a long time. Have you contacted Emotiva support for help? If so, what did they say? If not, suggest you call them Monday morning.

BTW, is this the case with the USB as the last input selected when the Xda-2 was used previously? I'm wondering if the delay is when the USB input is selected after powering on.