Did We Overhype USB Audio And Overlook Possible Pitfalls?

[wgscott]

Optical or wireless transmission have the inherent advantage of electrical isolation. I wonder if as much time and as many resources were placed into developing either of these, whether they would be ahead of where USB is now?

[The Computer Audiophile]

Optical or wireless transmission have the inherent advantage of electrical isolation. I wonder if as much time and as many resources were placed into developing either of these, whether they would be ahead of where USB is now?

I really wish optical would be perfected.

[Jud]

Optical or wireless transmission have the inherent advantage of electrical isolation. I wonder if as much time and as many resources were placed into developing either of these, whether they would be ahead of where USB is now?

 

Isolation from the transmitter, yes. But even with USB this may not be the main problem. A bigger problem may be the electrical activity of the receiver on the DAC's PCB.

[wgscott]

Isolation from the transmitter, yes. But even with USB this may not be the main problem. A bigger problem may be the electrical activity of the receiver on the DAC's PCB.

 

So would feeding a DAC via coax input from a USB to coax converter be a better path (all else being equal)?

[vortecjr]

Not a single mention of i2s/dsd:)

[tranz]

I really wish optical would be perfected.

 

Optical LAN is a nice go between available now.

 

Not a single mention of i2s/dsd:)

 

My fav - bypass SPDIF and USB....straight to I2S.

[mansr]

Not a single mention of i2s/dsd:)

 

I2S is is a trivial clock+data serial interface only suited for short links, typically on the same PCB or over a very short cable, due to the lack of any error correction. For transmission from a computer to a different device, you really want something using differential signalling and at least some amount of error correction.

[cjf]

I've been using USB as my primary means of audio input to a DAC for many years. I've had my share of issues with Windows based systems that required some sort of driver to make it work properly but since moving to a linux platform all my USB troubles have disappeared.

 

I've often wondered what benefits many of the USB tweaks on the market are really offering when used with a properly designed DAC. As an example, if a DAC takes all the bits from USB into an internal buffer (think Meitner..etc) and then that buffer is what feeds the chip responsible for DA conversion then any jitter at the USB cable connection should be a non-issue, in theory. This method would be in comparison to the DAC's that drink straight from the tap so to speak without any form of buffering. It seems there are many of the later type of DAC's on the market using USB as a primary means of Input. So, when considering a DAC that does use this buffering and then if you read about a DAC of this type having crappy Jitter measurements I would like to think it doesn't really matter considering how it handles the data after the USB Input jack anyway.

 

I think the ideal Input would be Fiber based. Maybe into a black box outside the DAC chassis to isolate any noise generated by the SFP itself. That then leads us to what the output format would be from this black box into the DAC. I'm thinking maybe an old school ribbon cable or similar at a very short length.

 

So who's going to be the first one to make this contraption?

[The Computer Audiophile]

I2S is is a trivial clock+data serial interface only suited for short links, typically on the same PCB or over a very short cable, due to the lack of any error correction. For transmission from a computer to a different device, you really want something using differential signalling and at least some amount of error correction.

There is no error correction in USB audio.

[vortecjr]

I2S is is a trivial clock+data serial interface only suited for short links, typically on the same PCB or over a very short cable, due to the lack of any error correction. For transmission from a computer to a different device, you really want something using differential signalling and at least some amount of error correction.

 

Yes and no:

no - why would you need LVDS if you have a network DAC that excepts Ethernet input and outputs i2s/DSD to your circuit.

yes - LVDS i2s for transmission.

 

BTW have you seen the inside of audio gear lately....nothing short about the audio signal paths;)

 

Jesus R

[mansr]

There is no error correction in USB audio.

 

USB packets have checksums to detect any single or double bit errors, and since it uses differential signalling, it is more robust against interference than I2S to begin with.

[Rexp]

I've been using USB as my primary means of audio input to a DAC for many years. I've had my share of issues with Windows based systems that required some sort of driver to make it work properly but since moving to a linux platform all my USB troubles have disappeared.

 

I've often wondered what benefits many of the USB tweaks on the market are really offering when used with a properly designed DAC. As an example, if a DAC takes all the bits from USB into an internal buffer (think Meitner..etc) and then that buffer is what feeds the chip responsible for DA conversion then any jitter at the USB cable connection should be a non-issue, in theory. This method would be in comparison to the DAC's that drink straight from the tap so to speak without any form of buffering. It seems there are many of the later type of DAC's on the market using USB as a primary means of Input. So, when considering a DAC that does use this buffering and then if you read about a DAC of this type having crappy Jitter measurements I would like to think it doesn't really matter considering how it handles the data after the USB Input jack anyway.

 

I think the ideal Input would be Fiber based. Maybe into a black box outside the DAC chassis to isolate any noise generated by the SFP itself. That then leads us to what the output format would be from this black box into the DAC. I'm thinking maybe an old school ribbon cable or similar at a very short length.

 

So who's going to be the first one to make this contraption?

Hi, I'm a bit confused. In your system, is it the fact you're using a linux based server or that your DAC buffers the incoming USB feed that has solved your USB troubles? Have you tried your server with a DAC that doesn't buffer the input? Cheers

[The Computer Audiophile]

USB packets have checksums to detect any single or double bit errors, and since it uses differential signalling, it is more robust against interference than I2S to begin with.

I'll repeat, USB audio has no error correction (as told to me by the Godfather of USB audio, Gordon Rankin).

[mansr]

Yes and no:

no - why would you need LVDS if you have a network DAC that excepts Ethernet input and outputs i2s/DSD to your circuit.

 

Ethernet is differential. I2S is fine within a single device, not between different devices.

 

yes - LVDS i2s for transmission.

 

I2S is by definition single-ended. You can of course send the same signals over a differential link using suitable transceivers, but then it's not really I2S any more.

 

BTW have you seen the inside of audio gear lately....nothing short about the audio signal paths;)

 

We're still talking about inches. The distance from a computer to a DAC is typically several metres.

[mansr]

I'll repeat, USB audio has no error correction (as told to me by the Godfather of USB audio, Gordon Rankin).

 

I just checked the USB 2.0 spec. It has CRCs for each packet. The USB audio layer doesn't add any additional error correction.

[The Computer Audiophile]

I just checked the USB 2.0 spec. It has CRCs for each packet. The USB audio layer doesn't add any additional error correction.

Isochronous USB (used for adaptive and asynchronous audio) can identify errors but has no error correction.

 

Seriously, ask Gordon or John Swenson or someone who has worked with USB audio extensively.

[Jud]

No one makes a DAC without a buffer. No this doesn't make a DAC immune to jitter, even theoretically, though it does prevent gross errors that would occur if the DAC ran out of data in the middle of a track.

[Jud]

So would feeding a DAC via coax input from a USB to coax converter be a better path (all else being equal)?

 

For me personally, it was not, and neither was USB -> Toslink or coax -> Toslink (by a long shot). For some folks a converter sounds better; for me and others, USB has been the best so far.

 

All anecdotal (on my part anyway), so up to you how much credit to give it.

[wgscott]

For me personally, it was not, and neither was USB -> Toslink or coax -> Toslink (by a long shot). For some folks a converter sounds better; for me and others, USB has been the best so far.

 

All anecdotal (on my part anyway), so up to you how much credit to give it.

 

 

My Nova's USB input is only 16 bit, 44.1 or 48 kHz, so I have to go optical or coax. Coax seems to be the most reliable. Someday I may get a new DAC, so I was just wondering ...

[wanta911]

USB Audio has created a never ending stream of add-on products to make it sound better. I concede that this applies to a lot of products but it seems that the USB Audio improvement business is doing particularly well and therefore the demand is particularly high? You could argue that this is based on sheer numbers (most DACs come with a USB input) or there is something inherently wrong with the format in the first place. I subscribe to the latter.

 

I also don't understand why new supposed audiophile products are being released (Aurender streamer/servers for example) with only USB digital outputs? If I wanted to buy an Aurender with other output options, it will cost me AUD 13,500 for an N10!

 

For the manufacturers, is it a case of convenience over function/performance?

[vortecjr]

Ethernet is differential. I2S is fine within a single device, not between different devices.

 

I2S is by definition single-ended. You can of course send the same signals over a differential link using suitable transceivers, but then it's not really I2S any more.

 

We're still talking about inches. The distance from a computer to a DAC is typically several metres.

 

I have no issue sending i2s/DSD between two boxes in LVDS format and the boxes are a meter apart. I have no issues putting it up against USB DACs or ethernet DACs. I have been doing it for years and I have direct feedback from customers. You can't simply brush it off....

 

Jesus R

[vortecjr]

My Nova's USB input is only 16 bit, 44.1 or 48 kHz, so I have to go optical or coax. Coax seems to be the most reliable. Someday I may get a new DAC, so I was just wondering ...

 

They have a mix of adaptive USB and asynchronous USB based products. This happened to many companies during a period where things where changing very quickly. That one sounds like the one that is adaptive USB. Use it for streaming internet radio...

 

Jesus R

[vortecjr]

For me personally, it was not, and neither was USB -> Toslink or coax -> Toslink (by a long shot). For some folks a converter sounds better; for me and others, USB has been the best so far.

 

All anecdotal (on my part anyway), so up to you how much credit to give it.

 

This is fair.

 

I see a bunch of expensive devices with cheap third party USB receivers boards and the owners love the equipment. Can you argue with a happy customer?

 

Jesus R

[YashN]

Isochronous USB (used for adaptive and asynchronous audio) can identify errors but has no error correction.

 

Seriously, ask Gordon or John Swenson or someone who has worked with USB audio extensively.

 

 

Correct, but he was mentioning CRC, this is a 'Check', not a correction.

[ringenesherre]

For most people, the thought of setting up an Ethernet DAC leaves them cold. Not talking about enthusiasts who will venture into the unknown. A direct cable connection to a computer and installing a simple setup program (or none at all) is slightly easier to grasp.

 

For 2016 notebooks, what connections are available for digital audio.

 

I disagree. There is a connection available on all 2016 notebooks that is better at isolation and much more widely employed to transport audio to playback devices than USB.

 

We are, of course, talking wifi and technologies such as airplay, chromecast or roon.

 

If we want to improve quality of ubiquitously available audio playback, we should focus on getting good endpoint implementations of these technologies.