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post #466 of 783

Interesting questions bigshot. As it might be semi-related could I point you clever lot at this thread http://www.head-fi.org/t/620094/dropouts-in-foobar-over-spdif-with-boinc-and-eist-solved

 

In short, I used to run intensive computing progs in the background while listening to music through an Asus DX -> CA Dacmagic. Occasionally you'd hear very tiny clicks, but they were so quiet and brief as to be ignorable and I didn't realise it was a problem. Then I swapped the DX out for an M-Audio 2496 and it was terrible! Clicks more frequent and more disruptive to the music. However with BOINC switched off and speedstep disabled it was fine. Recently I've been using an AMB gamma2 (gone back to the DX) and it must be far more robust (it has a clever asynchronous something-or-other) as it seems to be immune to any of these problems regardless of what else is running.

 

So what were these noises I was hearing? Perhaps they were this mysterious "jitter" caught in the act? Or buffer under runs? You can try the same thing yourself using a cpu stress test - something like prime95, Intel Burn Test, or LinX, and listen out.

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post #467 of 783
Quote:
Originally Posted by joeyjojo View Post

So what were these noises I was hearing? Perhaps they were this mysterious "jitter" caught in the act? Or buffer under runs? You can try the same thing yourself using a cpu stress test - something like prime95, Intel Burn Test, or LinX, and listen out.

 

It was the sweet sound of missing and/or wrong bits.


Edited by ultrabike - 9/21/12 at 2:16pm
post #468 of 783
Quote:
Originally Posted by bigshot View Post

Quote:
Originally Posted by grokit View Post

Random results often provide for the gestation of pure genius.

That's how evolution works! If you're willing to wait from the Pleistocene to the Paleozoic for your sound quality to improve, random mutation is the way to go. I'm just a little too impatient for that myself.

 

Not random mutation, trying random tweaks to see what sticks. Who knows, could get lucky!

post #469 of 783
Quote:
Originally Posted by grokit View Post

 

Not random mutation, trying random tweaks to see what sticks. Who knows, could get lucky!

 

HiFi audio Vegas style baby! cool.gif

post #470 of 783
Roll dem bones! Papa needs a new pair of cans!
post #471 of 783

http://en.wikipedia.org/wiki/Infinite_monkey_theorem

 

 

don't expect them to do any better with soldering irons instead of typewriters

post #472 of 783
Quote:
Originally Posted by ultrabike View Post

 

It was the sweet sound of missing and/or wrong bits.

 

yes this would be my guess as well, dropouts are not jitter IMO.

post #473 of 783
Quote:
Originally Posted by bigshot View Post


I don't think a basic understanding of how digital audio works is all that difficult. I think people are just too lazy to do the googling, so they assume spending a lot of money will get them the sound they want without going to all that trouble. They're lazy and they pay through the nose for it. Audio is pretty straightforward, and once you know how your ears work, you can give them what they need. It isn't difficult or expensive.
It's been my experience that when technical explanations start turning to swamps of molassas, it's because someone is starting to count angels dancing on the heads of pins. For instance, I'd love to have someone explain to me what jitter actually sounds like. When I spent a few days puzzling it all out, I came to the conclusion that not only is it extremely rare in home audio, it occupies a time frame so tiny, ears would likely pass right over it. Repeating patterns of gross amounts of jitter might affect upper frequencies, but I have yet to hear anyone say it sounds like that. That's probably because jitter flat out doesn't affect sound in any audible way.

 

I think it also depends on where the jitter is in the audio stream as well as what type of jitter, which are the components being affected, what are the jitter reduction mechanisms etc.  I agree 100% about throwing the money at the "problem."  I think there are a lot of misconceptions about computer audio and digital transports/cables, most of them probably inspired by some audiophile products/companies marketing material.  From my own experiences I have heard influence of some USB controllers, galvanic isolation etc. that spans the entire frequency spectrum as increased bloom and lack of focus - I have no idea how that works (none of the tweaks were better than USB straight out of the motherboard IMO.)  Keeping things simple, high quality and direct seems to win out over buying into miracle components, but some people seem to think that digital should sound like analog, and therefore that anything that sounds different to analog is jitter, forgetting that analog has much lower timing accuracy....

post #474 of 783
I have a $120 Sony bluray player.it has no audible jitter. Jitter is not an audio problem. It's a sales tool.
post #475 of 783
Quote:
Originally Posted by bigshot View Post

I have a $120 Sony bluray player.it has no audible jitter. Jitter is not an audio problem. It's a sales tool.

 

I thin it might be both a sales tool and an audio problem, just that the problem is some audiophile companies selling products that actually perform badly and colour the sound.  I have no evidence for this but this is what I think is going on.

post #476 of 783
It's pretty simple then to just buy inexpensive midline gear that outperforms the expensive stuff.
post #477 of 783
Last night I decided to park myself in front of the desktop instead of the laptop,
Took my dacportLX with stock usb with me n a HM5 along. Opened up tuneIn radio ...bossa nova ..nice.

Then I when back to my living room n hijacked a furutech gt2 USB cable n plugged it in...
The sound went from from nice to wowwww...I just love the whisky n the placebo..amazing furutech...slurpsssss.
This is FUN!!!

wink.gif
post #478 of 783
Quote:
Originally Posted by Lorspeaker View Post

Last night I decided to park myself in front of the desktop instead of the laptop,
Took my dacportLX with stock usb with me n a HM5 along. Opened up tuneIn radio ...bossa nova ..nice.
Then I when back to my living room n hijacked a furutech gt2 USB cable n plugged it in...
The sound went from from nice to wowwww...I just love the whisky n the placebo..amazing furutech...slurpsssss.
This is FUN!!!
wink.gif

post #479 of 783
Quote:
Originally Posted by bigshot View Post

I have a $120 Sony bluray player.it has no audible jitter. Jitter is not an audio problem. It's a sales tool.

 

An interesting observation I made was with my Audiophilleo USB converter. Though it has jitter independently measured at below 1ps, I still felt there was some degree of unpleasant harshness in my system. Using it out of a better power supply (and not using the computer's power) improved things. Indeed, an upgrade to the power supply for it is not intended to improve the jitter at all, but improve the performance of the S/PDIF output. That removed the perceived harshness*.  I'm using this to illustrate a point, which is people tend to classify everything they think is wrong with digital audio to be the result of "jitter" when what is going on is fare more complex and are not something that needs a cable change to improve.

 

*Without the necessary $10k+ of equipment required to test what was going on accurately, I have no other means of testing what is going on, but as I've been saying for a while now, I'd like to be able to.

post #480 of 783

From what I've read so far, my understanding is that audible jitter is due to instantaneous and random variations of the DAC clock frequency. Since most USB audio transfers use Isochronous/Adaptive mode, clock is derived from the somewhat jittery USB data bits, resulting in a somewhat jittery DAC clock. Jitter in the data path may be due to poor host master clock, power sub-system noise (see Currawong above), horrible PCB trace issues, EMI/RF through the cable, etc... Several methods exist to attenuate said jitter like TI's SpAct deal in their pcm2704/5/6/7 ICs (http://www.ti.com/lit/ds/symlink/pcm2707.pdf)... There might be some re-clocking and alternative schemes to further reduce this jitter, like Benchmark's DAC1 UltraLock deal.

 

As far as, how does jitter sound, in the case of a turntable or cassette player, the motor speed might instantaneously and randomly fluctuate... 'cuz motors are not infinitely precise. This would result in the analogous of DAC clock jitter. One could go DJ crazy on the turntable and hear crazy jitter. If jitter is bothering your ears, a good DAC might help (that is not necessarily the most expensive one, research helps.)

 

As far as cables, they act as low pass filters which smear the signal, and result in jitter. A good, standards compliant and not necessarily expensive USB cable, should keep things relatively clean AFAIK, along with a well regarded/proven USB interface/receiver solution.

 

There is one type of jitter that no amount of cables and true reference level USB receivers will be able to correct AFAIK: jitter in the actual recording.


Edited by ultrabike - 9/23/12 at 1:11am
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