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Digital music transmission via USB - Page 3

post #31 of 58
You left out psychological
post #32 of 58
Quote:
Originally Posted by proton007 View Post

 

The sources of jitter are considered to be Random (Gaussian) or Non-Random (Crosstalk/Power ripple/Temperature/Vibration). 

There are numerous factors that affect jitter. The characteristic of random jitter could be Gaussian but is not the source. The source of jitter is not well known. There are many papers on it. It could be the instability of the junction of the transistors, random electron shot noise etc.It is a very complex topic to discuss here. It is true vibration could be a factor influencing jitter. Since the circuit is solid state (assumption), vibration is a very small factor. The only part I think might be affected by vibration is the quartz crystal oscillator. However, in real application the jitter generated is not critical. A quartz watch uses low grade quartz and has major vibration issue and yet they still maintain good accuracy. I am not an expert on the watch. So unless the watch has equal jitter amplitude on both rails, vibration IMO does not do much to generate jitter.

 

I'll be happy to address the other factors, but I think it'll put people to sleep. In summary, the major contributor of jitter are the clock recovery circuit, bandwidth of the transistors in use and the driver.

post #33 of 58
Quote:
Originally Posted by dvw View Post

There are numerous factors that affect jitter. The characteristic of random jitter could be Gaussian but is not the source. The source of jitter is not well known. There are many papers on it. It could be the instability of the junction of the transistors, random electron shot noise etc.It is a very complex topic to discuss here. It is true vibration could be a factor influencing jitter. Since the circuit is solid state (assumption), vibration is a very small factor. The only part I think might be affected by vibration is the quartz crystal oscillator. However, in real application the jitter generated is not critical. A quartz watch uses low grade quartz and has major vibration issue and yet they still maintain good accuracy. I am not an expert on the watch. So unless the watch has equal jitter amplitude on both rails, vibration IMO does not do much to generate jitter.

 

I'll be happy to address the other factors, but I think it'll put people to sleep. In summary, the major contributor of jitter are the clock recovery circuit, bandwidth of the transistors in use and the driver.

 

You're right, the terms I used refer to a quartz oscillator. And yes, the jitter itself would display Gaussian distribution, not the source.

 

That said, two things are certain. One, the effect of jitter on sound is greatly exaggerated. A simple google search can reveal that there's a certain threshold for jitter, below which its effect is inaudible (-110 dbFS if I'm not wrong). While there are well engineered products like the Benchmark DAC which will outperform a lot of popular DACs when it comes to these measurements, they're merely pushing the envelope further without actually having any significant effect on sound.

Two, it leaves the cable out of the picture, because the DACs will generate their own clock.

post #34 of 58
Quote:
Originally Posted by ab initio View Post


I want to have the high level technical discussion here---

Then you'll have to invite experienced manufacturers to discuss the issue and/or do some measurements with a variety of modern DACs. So far we've only had Jaydee and Dan Lavry post anything in detail about USB audio. Everyone else, including me, isn't qualified or experienced enough to really get into the technicalities of it. 

 

Quote:
Originally Posted by ab initio View Post

I'm pretty sure it's $30 for the USB S/PDIF converter and $1,270 for the weapons-grade uranium that the housing is milled from--- remember, that started as a single billet before it got CNC'd down to it's final form. 

 

IIRC it has a 6-layer circuit board, which isn't cheap and the unit is sealed shut so it cannot be serviced, so if it breaks under warranty he has to replace the whole thing for the customer at his own expense.

 

FYI, I think expensive USB cables are a waste of money too.

post #35 of 58
I just solder all my USB to http://www.ti.com/product/cdcm7005.

Then I am listening to sound as if a dirty window was just washed.
post #36 of 58

Just considering the USB cable itself, I think it really shouldn't have much problems. Sending a digital signal down (essentially) a wire should be able to disregard the problems of noise and distortions common to analogue circuitry, unless timing delays were somehow introduced somewhere, but that wouldn't be caused by the cable itself.

 

Now I haven't yet read the rest of the thread, but the real problem here, I assume, lies in whether the thing (whatever manages the usb signal) sending the signal out is able to do so without much distortion, and finally if the thing receiving it does not as well. The DAC might be more important though.

 

Finally, I personally have not heard a difference switching from usb, to an expense coaxial cable, and back. I don't think the type of connection really matters in the end, in terms of audible quality.

post #37 of 58
Quote:
Originally Posted by Pazz View Post

Just considering the USB cable itself, I think it really shouldn't have much problems.

No no no. You see, I heard some manufacturers (mind you, of audiophile components) talking and they clearly said there's more going on than just transmitting a digital signal. They have to be right because they design and sell really expensive stuff. Don't ask about any details though. If I think about it, don't even ask about basic stuff. rolleyes.gif

 

On a more serious note, that's the perfect example of FUD. This paranoia is what prompts (I'd go as far as saying forces) audiophoiles to waste their money on this nonsense.

==> Credibility of audiophilia -1 which makes an unchanged total of 0.


Edited by xnor - 8/1/13 at 10:11am
post #38 of 58
"...paranoia...forces audiophiles..."
It is a "force" that's part of this hobby and difficult to overcome. I was there years ago.

Let's now hear from a psychologist, if one belongs to this site.
Edited by Mambosenior - 8/1/13 at 10:37am
post #39 of 58
Quote:
Originally Posted by Mambosenior View Post

"...paranoia...forces audiophiles..."
It is a "force" that's part of this hobby and difficult to overcome. I was there years ago.

Let's now hear from a psychologist, if one belongs to this site.

 

I have two degrees in Psychology (BA and MSc)[1] but never bothered getting chartered - however you don't need any to recognize obsessional/rationalizing behavior and a host of other cognitive biases as these are pretty well documented

 

 

 

* 1 - despite these I have a certain skepticism about the value of psychology when it is not based on strong observational data, for instance it is suggested that psychological profiling is  "worse than useless"


Edited by nick_charles - 8/1/13 at 11:25am
post #40 of 58

"I'm not a Doctor, but I play one on TV..."

 

Only us old fogeys will get that one!

post #41 of 58
Quote:
Originally Posted by nick_charles View Post

 

I have two degrees in Psychology (BA and MSc)[1] but never bothered getting chartered - however you don't need any to recognize obsessional/rationalizing behavior and a host of other cognitive biases as these are pretty well documented

 

 

 

* 1 - despite these I have a certain skepticism about the value of psychology when it is not based on strong observational data, for instance it is suggested that psychological profiling is  "worse than useless"

 

I would concur with that. However, it would have been nice if I had had someone—back when I was in the throes of upgrading every component plus all signal and power cables in my system, and had become deaf to my kids and wife screaming to be fed outside my locked  listening room—to "talk" me down. Since I am positive that a previous post of mine detailing how I broke the "audio cable-spell" was instrumental in locking down another thread and causing replies to disappear, I wont reveal all details here. Suffice it to say that I encountered a pair of Home Depot ($8.99/ea at the time) power cables that didn't sound any different from $1200 cables (let's call them brand X) on my speaker system amps (Pass X600). For me, the path out of audiophilia nervosa started there, much to my relief. At this point in my life, I read cable advertising for the humor and with the same amount of cynicism I bestow on all reports that come out of Washington, D.C..

 

 

Quote:
Originally Posted by bigshot View Post

"I'm not a Doctor, but I play one on TV..."

 

Only us old fogeys will get that one!


Old fogey here. Still playing doctor with spouse.biggrin.gif

post #42 of 58
Quote:
Originally Posted by Mambosenior View Post

 

... it would have been nice if I had had someone—back when I was in the throes of upgrading every component plus all signal and power cables in my system, and had become deaf to my kids and wife screaming to be fed outside my locked  listening room—to "talk" me down. 

 

The problem is that your previous condition was not rational and so rational arguments may not have worked anyway[1], whereas you discovered "enlightenment" yourself... albeit the expensive way wink.gif

 

With me the spell-breaker was a simple switch box - best $20 I ever spent !

 

 

 

Quote:

1.Some people can't be told you know they have to learn the hard way - Elvis Costello

post #43 of 58
Quote:
Originally Posted by nick_charles View Post

The problem is that your previous condition was not rational and so rational arguments may not have worked anyway[1], whereas you discovered "enlightenment" yourself... albeit the expensive way wink.gif


With me the spell-breaker was a simple switch box - best $20 I ever spent !

Can I hear an Aaaaaaamen!


post #44 of 58
Quote:
Originally Posted by nick_charles View Post

[...] previous condition was not rational and so rational arguments may not have worked anyway [...]

You hit the nail on the head.

post #45 of 58
Quote:
Originally Posted by Currawong View Post

Then you'll have to invite experienced manufacturers to discuss the issue and/or do some measurements with a variety of modern DACs. So far we've only had Jaydee and Dan Lavry post anything in detail about USB audio. Everyone else, including me, isn't qualified or experienced enough to really get into the technicalities of it. 

 

With all due respect, I do not consider Jaydee and Dan are the "experienced" digital transmission expert. They might be brilliant engineers in audiophile equipment, but they still buys the USB transceivers and did not design one themselves. I think some of the members on this board have considerable technical skill and are perfectly qualified to discuss this topic.

 

It is bad manner to post one's credential in a Internet forum. But you must be asking who are you to judge and what's your qualification. I have seven patents in digital communication. Full disclosure, they're not in USB only in Ethernet, but transmission theory is the same. I was also in the IEEE802.3 standard working group for over 10 years. I am not familiar with the USB DAC audio playback. However, I did design instrument DAC chips early in my career. I do believe I am perfectly qualified to discuss the USB transmission. This is not meant to be a put down, I apologize if I offended anyone. But this qualification issue kept coming up to nullify opinions, so I just want to clear the air.

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