USB Gremlins exposed!

[amirm]

Google does not. Nor does wayback machine.

 

[NorthSky]

I have just read those two links:
1. http://suiteminute.com/how-to-find-...osts-wayback-machine-and-googles-cache-video/
2. http://www.searchscribe.com/Legal/add-law-article/wayback-machine.htm

Amir, the USB audio world doesn't look easy as ABC?

 

[amirm]

Bob, it is easy. Folks try to make it hard to sell you things you don't need. Or justify buying things you don't need. I have multiple asynch. USB devices and all of them perform superbly.

 

[NorthSky]

Yes, you previously said to use USB for high fidelity audio. ...HDMI for video (movies with audio of course).
USB is the computer audio connection, and for few other sources too.

And if someone doesn't have asynchronous USB?

 

[amirm]

And if someone doesn't have asynchronous USB?

You need to get one one . Your computer always has it. And today you can get DACs at $200 price point that have async USB. You can also get async USB to S/PDIF interfaces that cost that much to use your existing DAC. So it is an easy and cheap enough upgrade.

 

[NorthSky]

My computer always had it? ...My laptop too?

 

[amirm]

Sure. Async USB on the computer side has been there forever.

 

[RayDunzl]

My computer always had it? ...My laptop too?

Some history:

http://www.usb.org/developers/docs/devclass_docs/audio10.pdf

 

[NorthSky]

My laptop costed me the same price as my last BR player (Oppo 103).
The laptop has four USB ports and the BR player three.
I thought that because the BR player has no USB asynchronous port that it was the same for the laptop.
_______

I was thinking in terms of USB DAC, my mistake.

• USB Asynchronous DAC – By bypassing the low fidelity, poor quality DAC of traditional computer soundcards, the BDP-105 turns any computer into a high performing multi-media source by converting digital audio to analog through the ESS Sabre32Reference DAC.

 

[Cosmik]

You can also get async USB to S/PDIF interfaces that cost that much to use your existing DAC. So it is an easy and cheap enough upgrade.

Am I missing something here? As I see it, the chief (only?) advantage of asynchronous USB is that it eliminates two related problems: (a) the necessity for the DAC to adapt to an external sample rate which must always cause 'impurities' in the output, and (b) any influence the physical link might have. As soon as we re-introduce S/PDIF anywhere in the chain, aren't we back to square one..? (at least for that part of the chain)

The notion of a perfect, purist's digital audio system only applies to the very specific circumstance of a single DAC with local, high precision, low jitter sample clock, and a data stream whose rate can be controlled by the DAC. Luckily for us, this corresponds to the domestic audio system playing recordings. Asynchronous USB can implement this model, as does an integrated CD player. For more complex, real time systems such as might be encountered in a professional setting, this model may not work and so adaptive systems might be employed. But there is no need for us to contaminate our systems with such components.

 

[Phelonious Ponk]

So...my system goes wireless to an Apple TV, then optical to active speakers with built-in DAC. If I buy an outboard DAC, would it likely be worthwhile (audible while listening to music, not artifacts) to put a converter between the Apple TV and the DAC to use async USB?

Tim

 

[Cosmik]

So...my system goes wireless to an Apple TV, then optical to active speakers with built-in DAC. If I buy an outboard DAC, would it likely be worthwhile (audible while listening to music, not artifacts) to put a converter between the Apple TV and the DAC to use async USB?

If the Apple TV doesn't have asynchronous USB (hence the need for a converter..?) I don't think it would make any improvement to fit the converter. Optical to active speakers with built in DAC is an elegant system anyway, so if it was me, I would stick with that, and only worry about asynchronous USB and external DACs if I was starting from scratch. (And I am not claiming I would ever hear a difference, by the way).

 

[amirm]

Am I missing something here? As I see it, the chief (only?) advantage of asynchronous USB is that it eliminates two related problems: (a) the necessity for the DAC to adapt to an external sample rate which must always cause 'impurities' in the output, and (b) any influence the physical link might have. As soon as we re-introduce S/PDIF anywhere in the chain, aren't we back to square one..? (at least for that part of the chain)

In the abstract you are right. In practice, if you are using the motherboard S/PDIF interface on a computer, you are way better off using an async USB interface with isolation.

Here is an example in the form of low-cost/low-end converter driving a DAC with high susceptibility to noise and jitter. First, an RME audio card in the PC driving that DAC with optical S/PDIF cable: http://www.stereophile.com/content/...if-converter-measurements#X4tjs0mb8lBE9Qmi.97

As always the center spike is our source signal and everything else to its sides are distortions/jitter.

This is what happens when we instead use the Halide USB to S/PDIF interface:

We see a much better response.

Now, you could invest in a high-performance sound card such as Lynx in the computer and get similar benefit. But then you are married to an internal card that can and has become obsolete, requires proprietary drivers, does not work on a laptop, etc.

As a practical matter, modern laptops and computers have nothing but USB ports anyway. So if you are going to hook that up to a legacy DAC with only S/PDIF input, it makes much more sense to use a USB to S/PDIF interface than getting a "sound card" and having it drive S/PDIF.

 

[Fitzcaraldo215]

Sure. Async USB on the computer side has been there forever.

Yes, the hardware capability has been there on the PC side to support it. But, to make asynch USB audio work, it requires an asynch USB DAC or other device supporting asynch USB on the receiving side plus, importantly, driver software on the PC side that supports asynch USB. That driver software is often DAC-specific.

 

[amirm]

Yes, the hardware capability has been there on the PC side to support it. But, to make asynch USB audio work, it requires an asynch USB DAC or other device supporting asynch USB on the receiving side plus, importantly, driver software on the PC side that supports asynch USB. That driver software is often DAC-specific.

The class driver in Mac supports async USB up to 192 Khz. On the PC, the same is true up to 96 Khz. Indeed that was the "discovery" which was a way to program a USB receiver in the DAC to work in a backward compatible way. If you wanted to install a driver, such a solution has always existed as evidenced in Pro audio cards/devices.