[Glassman]

for those curious about USB and jitter, read quickly though this..

USB audio has some great potential, which is unfortunately never utilised in practice.. for the time being, USB audio is actually pretty *****..

 

[stryker]

From an email by pburke without his permission.

That USB discussion on headfi - amazing that you keep hearing the same
datasheet stuff over and over again. What these types don't do is
actually build such a thing and compare it. USB in itself is not jitter
free, but if you use a fast PC, have nothing else on the USB, isolate it
from the DAC, and then do everything else right (like put a Tent clock
with clean battery supply on the USB chip), these things can sound
amazing. I am certain that my current DAC sounds better than anything
under $2500 on the market. There's a lot of distracting information
being spread by some folks, too, mostly by industry people who are
working on competing products

As to whom he is talking about...? Well...let's just say it's people who have a vested/financial interest in bashing USB.

 

[Jon L]

Quote:

Originally Posted by Glassman for those curious about USB and jitter, read quickly though this.. USB audio has some great potential, which is unfortunately never utilised in practice.. for the time being, USB audio is actually pretty *****..

Yup, USB still has great room for better implementation. All we need is one big company (like TI) to realize there is a market for asynchronous USB transfer chips and then have a few of their programmers work on the software. Perhaps we can start a letter-writing campaign to TI to demand such a chip.

As far as that thread involving JohnW, what puts me off is the lack of LISTENING comparisons in a controlled environment with revealing gear/speakers. Also, can anyone confirm who JohnW is? Someone claimed before that he's a manufacturer and that he makes traditional spdif transports, which if true...

 

[Glassman]

he's not producing anything now nor has he produced anything during past few years.. he did listened to it, but that was not the object of that thread.. it's purely about the presence and character of jitter on the outputs of commonly used USB chips and comparison with recovered S/PDIF from regular CD player.. nothing less, nothing more.. just remember the graphs and numbers next time someone's gonna mix the words 'low jitter' with 'USB'

oh and it's not as much Ti's fault as is Microsoft's (again) who failed to implement that part of USB Audio specification, hence all the manufacturers are designing chips for isochronous mode, because that's the only one Windows drivers support.. it takes no more than writing custom WDM + ASIO drivers.. general purpose USB chips are readily available..

 

[Daroid]

I'm using USB myself, and to be honest, it so-to-say beats the crap out of the optical out on the RME to optical toslink input on DAC. I'm not sure if the toslink input is good or not, the coax part was really amateurish with a 75R resistor with a cap shunted to ground, not isolated, nothing.
The transformer coupling helps tremendously, compared to the USB input on the dac, it is much clearer, transparency is better. It was not coupled at any point inside the dac.

 

[thomaspf]

Quote:

Originally Posted by Glassman oh and it's not as much Ti's fault as is Microsoft's (again) who failed to implement that part of USB Audio specification, hence all the manufacturers are designing chips for isochronous mode, because that's the only one Windows drivers support.

Last time I hooked up a USB DAC that supported asynchronous USB (Audigy 2NX), Windows detected it as such and it worked out of the box in asynchronous mode with the standard Wndows driver.

I think his one is back to TI.

Cheers

Thomas

 

[stryker]

Quote:

Originally Posted by Jon L As far as that thread involving JohnW, what puts me off is the lack of LISTENING comparisons in a controlled environment with revealing gear/speakers. Also, can anyone confirm who JohnW is? Someone claimed before that he's a manufacturer and that he makes traditional spdif transports, which if true...

Well, I've heard the same from another reliable source. Specifically, that he is hoping to sell some dedicated rip to hard drive solution box that allegedly has minimal jitter. If true, that would certainly raise my eyebrows as to his specfic opinions and "intepretations." There's also another guy names "fmac" who is also known for the same opinions on asylum.

 

[Glassman]

Quote:

Originally Posted by thomaspf Last time I hooked up a USB DAC that supported asynchronous USB (Audigy 2NX), Windows detected it as such and it worked out of the box in asynchronous mode with the standard Wndows driver. I think his one is back to TI. Cheers Thomas

if it's for real than I just don't get it.. that would certainly ease the things, one would only have to implement USB Audio stack on a general purpose USB controller and be done.. in any case I don't believe they're taking full benefits of asynch mode in Audigy2 NX, meaning you won't find two different oscillators inside, but maybe.. can I ask you kindly to take a picture of the board?

whether JohnW will sell any equipment or not, that can't change the facts as they've been measured and presented.. the jitter is there and it's with significantly higher level compared to ordinary CD player->S/PDIF chain.. that does not necessarily indicate what the sound will be though.. jitter produced by USB chips has different properities than that of S/PDIF induced jitter - audible effects will be different too and it seems like people prefer the USB kind of jitter over the S/PDIF one, even though it's arguably much higher in amplitude.. so talk about the resulting audible effect and not about jitter itself because it really isn't low, much to the contrary..

 

[00940]

Stryker : there is a difference in practice between the technically best solution and the best sounding solution. The DDDAC Pburke loves so much is far from outstanding technically speaking. The SPDIF receiver section is as basic as it can get, the DAC chips used have terrible distortion and noise figures, the asynchronous reclocking is a complete waste of the tent clock in theory. The DDDAC is all about pushing old stuff to its best. Does that mean that it sounds bad ? You'd indeed have to listen to know.

It is no USB bashing to say that, as far as we know today, basing ourselves on both the results published by JohnW and on the technology as described in the USB white papers, there is no reason to say that USB as commonly implemented is perfect or so much better than SPDIF, technically speaking. The burden of the proof is on those who claim that USB is technically very good. We're waiting for results contradicting JohnW.

However, it might be true that it sounds better. Maybe because it's harder to mess up the receiving circuitry or because the properties of USB jitter aren't the same as SPDIF jitter.

 

[stryker]

In the interest of science, I will purchase a glass toslink and do a comparison between my modified DVP-S7000 and my computer as a source, switching between the coax and the toslink input. That's as close as I can get to a true A/B. If USB sounds better to me, it is better. If not, I will go back to the cd route. All I want is the best sound from a given source.

I believe that if Peter thought that the signal coming from his cd transport was better he would stay that route. However, to his ears, the USB route sounds better. He's a passionate audiophile who just does stuff to get the best sound, like most of us here. I would do the A/B tonight if I had a glass toslink on hand. Best Buy don't carry none.

I'll post my opinions on the matter when I get it all set up. However, regardless of source, the DDDac itself sounds exceptional when stacking 16 of those battery-powered noisy dacs all together and having the signal come straight off the chips with no I/V conversion. I can't go wrong either way.

 

[thomaspf]

I don't have access to the Audigy 2NX any more but I can asure you that the Windows USB audio driver support asynchronous mode. Creative is using a generic USB controller from Philips and has programmed the audio part.

I have no doubts that most current USB solutions are pretty bad with regards to jitter. There is mostly hype and creative marketing around most solutions.

Cheers

Thomas

 

[5Kurt]

Quote:

Originally Posted by thomaspf I have no doubts that most current USB solutions are pretty bad with regards to jitter. There is mostly hype and creative marketing around most solutions.

What is your opinion about the best non-USB solutions?

A good internal soundcard (eg lynx) with good old RCA outputs , Firewire DACs' or anything else?

 

[Glassman]

Quote:

Originally Posted by thomaspf I don't have access to the Audigy 2NX any more but I can asure you that the Windows USB audio driver support asynchronous mode. Creative is using a generic USB controller from Philips and has programmed the audio part. I have no doubts that most current USB solutions are pretty bad with regards to jitter. There is mostly hype and creative marketing around most solutions. Cheers Thomas

thanks for the information.. I'm just reading through the whole USB Audio Class spec as well as relevant parts of the USB 1.1 spec and they describe asynchronous isochronous mode as the most basic one while the adaptive isochronous is the most advanced in their eyes.. funny.. I think I'm eventually going to program up one of the general purpose controllers, because in adaptive mode, there can be as much as +/-1000ppm error, which is out of the reach for any decent clock locking system, which typically only does +/-150ppm.. I was also quite surprised to see that you can set arbitrary bit depth as well as samplerate which means one can have 24bit/96kHz capability without any driver writing.. well, we'll see..

 

[thomaspf]

24/96 works fine for for me on the Audiotrak Optoplay without any additional driver.

There is someone in the PC forum on Audioasylum who has been trying to program asynchronous mode for one of the exisiting chips. I can't recall his alias from the top of my head but you might want to investigate and hook up with him.

Cheers

Thomas

 

[Scrith]

This thread is a bit confusing.

You have some people saying that USB cannot possibly be any good unless the device is using the asynchronous mode.

And you have people who have carefully compared their high-end audio cards to a (assumed non-asynchronous) USB solution and found that the USB solution is clearly better.

I personally have flip-flopped on this issue a few times. I loved my 1212M at first. But then I heard problems and tried an M-Audio Audiophile USB, which sounded OK but was just unusable because of the awful M-Audio drivers. A year later M-Audio released new drivers (brand new and written from the ground up, they say...I wonder if there was some USB tweaking here?) and I, again, performed an exhaustrive comparison between the 1212M and the Audiophile USB and the Audiophile USB came out on top. That's where I am now.

Has ANYONE ever compared a high-end audio card's s/pdif (toslink or coax) output to a reasonably well-implemented external USB sound device and found the audio card to be superior to the USB solution?

Oh...and how does something like the Audiophile Firewire measure up? I am interested in actual, live comparisons, not theoretical comparisons.