TPA - USB Transport

[Goto]

Originally Posted by thomaspf

What you describe is an asynchronous transmission mode where the master clock for reclocking the received bits is located on the recieving side. There is however a caveat. Interfaces like the original HiFace invented their own protocol and USB driver module to achieve this asynchronous transmission. While this is not a problem now I wonder for how long these companies plan to update their drivers. While the average lifetime of a computer is around 3 years I tend to keep my audio equipment for much longer. The way to deal with that problem is to look for interfaces that implement USB class drivers that are supported by the mainstream operating systems. For 24bit / 192 Khz playback that means USB Audio Class 2. MacOS and I believe Linux already support this latest USB Audio standard and it is a pretty safe bet that Windows will eventually do the same. This protects you from having a dead box in 10 years.

The XMOS controller that Russ is planning to use supports this standard, so does the update to the Hiface called the HiFace 2. Probably the cheapest option for projects right now is the Audio-GD USB upgrade kit which is based on the Tenor TE8802L chip that also supports USB Audio Class 2. Right now the board is $39 plus shipping. It does not, however, provide for galvanic isolation and all clock singals are derived from a single 12Mhz crystal.

While I wait for the XMOS module from Russ I ordered one of those so I can finally test out my build.

Cheers

Thomas

Thomas

I certainly agree that adoption of the Audio Class 2.0 standard for USB is desirable as it simplifies and removes reliance on proprietary drivers. With the long gestatiion period of the TPA XMOS implementation I have bought another product which relies on non-standard drivers. There is no Linux support consequently but that is no big deal for me (though for others a deal breaker I am sure) as I am committed to the Windows pllatform.

Committing to proprietary drivers is a risk longterm, but it does allow the possibility of optimised integration of driver and hardware, rather than the inevitably compromised integration of a universal approach. Standards-based engineering is fraught with the "interpretation" by one company or another in my own experience.

I will investigate the Audio-GD board as it seems very well priced. Worth a punt.

Thanks

Mark

[barrows]

There are those (who make USB interfaces with their own drivers which are not USB Class 2 Audio compliant) who purport the following to be true:

"...rather than the inevitably compromised integration of a universal approach"

There is no real world evidence that a USB Class 2 Audio compatible approach based on the XMOS chip is actually compromised in any way. To say it is "inevitably compromised" is entirely unsupported by the actual evidence of how well these interfaces are performing. And indeed, lack of Linux supprt is a real downside, as my experience is that low power, Linux (vortexbox and voyage/MPD) based server solutions handily outperfrom other platforms.

[thomaspf]

Agreed!

I am also running a Lindemann DDC 24/192 based on the Tenor chip and a USB Audio class 2 driver with great success.

Optimizing and updating drivers is not a task that many companies on this planet are good at. The native OS drivers go through an incredible test matrix that simply cannot be matched by any other company.

Cheers

Thomas

[Goto]

Chaps

This is veering off piste and I did not intend to inflame. My statement is made on the observation that standardised (that is engineeringn solutions set by international standards bodies, formal or otherwise) are always compromised in some way. That doesn't mean they don't work well enough - indeed the purpose of standardisation is to find a scheme that works well in most circumstances.

It is impossible to say whether a standardised or specialised driver will work better unless you can measure them in a particular system and analyse the results. It depend on lots of factors, not least the design goals of each solution, which will almost always be at least somwhat different.

I will say however that I will go for an optimum approach over a standardised approach any day. I have no interest in a merely acceptable solution which will be the best outcome of any standardisation process. You have to remember that none of this engineering is done for the benefit of audiphiles (we are a very fringe bunch, with very little commercial clout compared the mainstream) but to appease the demands of "mass market" multimedia computer product sales.

USB Class 2 audio is a good solution, easy to integrate with, plug and play for a growing portion of the overall market. It's unlikely to ever be the absolute best because it's real market doesn't demand that. Indeed, the proliferation of asynchronous reclocking devices seems to support the argument that this standard does not inherently solve any of the real engineering problems facing the computer audiophile.

More options is always good though, and the compliant solutions all seem to be coming in cheaper than the non-compliant route I've gone down.

(Barrows - I can entirely understand why USB Class 2 would appeal in a Linux environment. Surely your best hope of getting any sound out of the set-up!)

[thomaspf]

Having lived in the space of operating systems for the last 25 years or so I am less optimistic that any audiophile company will ever get their driver into a state that you won't need to buy the right computer to match the USB device you just bought.

Standardization is one part of the equation. Testing a controller and driver against a couple of thausend of different configurations tracking all new chipsets etc. is a completely different one.

I am not pushing back that one might be capable of designing a better transport in theory. In practice however I have not found that to be an approach that scales much outside the labs of the company doing that work.

In fact once an inbox driver exists, the whole ecosystem flips around. Every hardware vendor will optimize their devices to work reliably with that driver. Which over time will lead to most bugs being reported and fixed in that one driver.

However, if someone believes they get a benefit from a custom design, go for it.

Cheers

Thomas

[Goto]

Originally Posted by thomaspf

Having lived in the space of operating systems for the last 25 years or so I am less optimistic that any audiophile company will ever get their driver into a state that you won't need to buy the right computer to match the USB device you just bought.

Standardization is one part of the equation. Testing a controller and driver against a couple of thausend of different configurations tracking all new chipsets etc. is a completely different one.

I am not pushing back that one might be capable of designing a better transport in theory. In practice however I have not found that to be an approach that scales much outside the labs of the company doing that work.

In fact once an inbox driver exists, the whole ecosystem flips around. Every hardware vendor will optimize their devices to work reliably with that driver. Which over time will lead to most bugs being reported and fixed in that one driver.

However, if someone believes they get a benefit from a custom design, go for it.

Cheers

Thomas

In Englad we say "Swngs and Roundabouts...", good and not-so-great in every option.

Two years ago there were few choices - if any - in this arena. Now there are many and the advantage of the standardised approach should be better price/performance. Just not necessarily "The Best". And that is a whole other debate and not one for Russ and Brian's paid-for space I am sure! But DACs like the Buffalo have driven this demand in our smal corner of the audio market, so TPA have played a big part already in driving demand for better transport options.

We are all winning, I think.

Mark

[amix]

Originally Posted by barrows

would be off topic here, I will send you a PM...

Since this is the thread, where BuffaloII owners drool for a USB connect for one and a half year, it may be nice to share all knowledge available

[amix]

Hello,

I just want to add myself to those people interested in a Hi-Rez USB input for the Buffalo. Since I have the Buffalo-II I am fine with Stereo, though, I would welcome the 8 channel solution even more, since I may want to upgrade one day.

Oh, and please, keep it affordable ;-) The last time I checked the ExA-U2I it was over 400 USD !!!

[barrows]

Originally Posted by amix

Since this is the thread, where BuffaloII owners drool for a USB connect for one and a half year, it may be nice to share all knowledge available

really innappropriate to discuss competing products on the TPA forums. I am happy to share by PM, but also note that I am looking forward to the TPA solution, as I expect it will be a no compromise product which will provide the best possible sonic performance for a Buffalo DAC.

[Spirit02]

Originally Posted by barrows

really innappropriate to discuss competing products on the TPA forums.

Indeed. You tend to get ignored by Russ and Brian after doing so

Really looking forward to the USB-I2S converter so I can box up my BII