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Jitter -- How low is low?

post #1 of 151
7/19/08 at 8:30pm
Thread Starter 
What is considered a low number these days for a good modern dac? -- leaving aside the debate as to whether it matters. I know the Bryston CD player is supposed to be 116ps. Seems to me this number should always be posted by designers at least as a general idea of quality. I don't always see it. Maybe it's not about the number. Or that does not tell the qualities of the Jitter, some sounding good like tube distortion. These days the first thing I want to know about a dac is this number -- perhaps it's just a red hering.
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post #2 of 151
7/19/08 at 8:53pm
Gosh, I have never experienced jitter so I do not worry about it. Going digital certainly eliminated this problem for me.
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post #3 of 151
7/19/08 at 9:13pm
If you can see a number on the spec page, than it's too high
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post #4 of 151
7/19/08 at 9:53pm
Quote:
Originally Posted by breakfastchef View Post
Gosh, I have never experienced jitter so I do not worry about it. Going digital certainly eliminated this problem for me.
What do you mean? The concept of jitter only exists in digital domain, more specifically in DA conversion.
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post #5 of 151
7/19/08 at 10:06pm
Quote:
Originally Posted by Hadden View Post
What is considered a low number these days for a good modern dac? -- leaving aside the debate as to whether it matters. I know the Bryston CD player is supposed to be 116ps.
If I remember correctly, the theoretical limit of jitter for 16 bit audio is in the region of 120ps to raise above the 16 bit noise floor. What is audible is debatable. I have seen white papers about artificial jitter not being audible at 250ns. See for example pdf document.
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post #6 of 151
7/19/08 at 10:28pm
Quote:
Originally Posted by paul_lindemann View Post
If you can see a number on the spec page, than it's too high
Sir, you just made my "this guy is probably not worth disliking" list.
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post #7 of 151
7/25/08 at 11:09am
Here is another way of looking at it. In one picosecond light moves 0.0003 meters.


Now when was the last time your eyes saw a beam of light move 0.3 millimeters?


Do you think your ears can hear a signal shifting a few hundred pico-seconds?
.
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post #8 of 151
7/25/08 at 11:33am
Thread Starter 
There are a lot of hyper-rationalist in this hobby who are actually doctrinaire. Don't even listen. It's just silly to say a well designed dac is equivalent to any old cheapy thing and everyone is deluded and money-vain who thinks otherwise. I am as skeptical about these things as the next guy. It's just that there are an awful lot a heavy hitting designers that regard jitter as a legitimate concern. I know citing authority does not necessarily make something legitimate. Maybe I am a dumbass, but I have heard differences in digital that people attribute to jitter. Perhaps it's something else. Who knows. I just get tired when people say THERE IS NOTHING TO THIS -- CASE CLOSED. It's surely not that definitive -- and rather weird when someone comes across as though they do not possess any self-doubt. It's just being cultish at the other end of the spectrum.
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post #9 of 151
7/25/08 at 11:40am
There are huge differences in DAC's and in my experience it is due to the DAC chip and the analog stage of the design.
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post #10 of 151
7/25/08 at 11:43am
Don't listen to opinions. Go find out how small a space of time people are talking about. Then go out and figure out the perspective on just how small a change that represents.

There's time shifting in EVERY recording on an order of magnitude many many many times the figures being quoted by jitter "experts". It's called reverb. An easy way to find out how big a difference jitter makes would be to set up a reverb that operates in the picoseconds. Good luck being able to hear it!

The truth rarely lies halfway between two opposing opinions. Usually, someone is right and the other person just has a vested interest in being wrong. Jitter is infinitesimal in the overall impact of a stereo system.

See ya
Steve
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post #11 of 151
7/25/08 at 12:06pm
Quote:
Originally Posted by bigshot View Post

There's time shifting in EVERY recording on an order of magnitude many many many times the figures being quoted by jitter "experts". It's called reverb. An easy way to find out how big a difference jitter makes would be to set up a reverb that operates in the picoseconds. Good luck being able to hear it!
Heaven help us when the new turntable kids on the block discover that there is a time and phase difference between the sound at the beginning of a vinyl record and the end of it. That's unless you use a linear tracking arm. To me that phase and time shift is far more noticeable.

For the record, the jitter in a DAC chip could be zero, and still that would mean absolutely nothing in real term. The clock IC also has jitter, and the lowest jitter spec. receiver I know of is the DIR9001 with figures quoted at about 50ps. So unless your DAC etc. uses a DIR9001 you are suffering from loads of jitter at this moment in time. I bet you that you are now worried and you are going to look for anything with a DIR9001 in it.
Then we have jitter issues in the digital connection cables.

And whilst we are at it, the jitter figures for USB to I2S or SPDIF converters are horrendous. Still many come of head-fi and ask for a USB DAC. I myself only touch USB DACs in absolute emergency, but bot so much for their high jitter as for their diabolical dynamic range that is well short of the dynamic range of 44.1KHz/16Bit stereo. But do I hear those poor USB performance DACs being discussed in terms of jitter and dynamic range? Nope, since it would hurt sales of some frequently mentioned USB input only DACs.
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post #12 of 151
7/25/08 at 12:11pm
Funny you mention the DIR9001. I just built a DAC with the DIR9001. It doesn't sound any where as good as my other DAC that has a lowly CS8414. The difference is the CS8414 DAC has a top notch analog stage.
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post #13 of 151
7/25/08 at 12:33pm
There are certain tolerance that even the human brain cannot detect. Try catching a dollar bill dropped after being held just above your thumb and index finger. You cannot do it unless you cheat and know when the bill will fall. If person holding the bill drops it randomly your brain does not have enough time to send an impulse to close your grip.

I think some people can sleep better at night knowing their DAC has lower jitter compared to X even when a difference may not be audible.
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post #14 of 151
7/25/08 at 12:38pm
Quote:
Originally Posted by flashnolan View Post
There are certain tolerance that even the human brain cannot detect. Try catching a dollar bill dropped after being held just above your thumb and index finger. You cannot do it unless you cheat and know when the bill will fall. If person holding the bill drops it randomly your brain does not have enough time to send an impulse to close your grip.

I think some people can sleep better at night knowing their DAC has lower jitter compared to X even when a difference may not be audible.

All senses are dependant on nerve impulses, electrons don't move faster than the speed of light. In fact nothing does.
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post #15 of 151
7/25/08 at 2:18pm
Quote:
Originally Posted by regal View Post
snip electrons don't move faster than the speed of light. In fact nothing does.
....that at present we can measure or know about
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