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Anti-jitter RAM buffer in DACs, Which have one ?
Pio2001
post Aug 3 2003, 10:00
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In, http://www.tc.umn.edu/~erick205/Papers/pap...html#principles we can read about RAM buffers :

QUOTE
This process is referred to as timebase correction and as stated before, any quality piece of equipment will implement it.


That has been the ritual answer to jitter concerns since I'm on the Internet.

But... if "any quality piece of equipment will implement it", then some non-quality pieces of equipment don't implement it. My question is : which ones ?

The statement "quality piece of equipment" is completely subjective and doesn't give any information. For my grandfather, a "quality" CD reader will be a portable radio-cassette-CD-speakers combo for 100 $ in the supermarket. The "non-quality" one will be the Fisher-Price toy for children from 3 to 7.
For an audiophile friend, the "quality" CD player will be the 25,000 $ Wadia CD Transport+DAC, while any player under 1,500 $ is just worthless crap.

So, do a 200 $ CD Player always have a RAM buffer ? Or is it not considered a quality piece of equipment ? What about a 300 $ CD Player from 1990 ?
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Pio2001
post Aug 14 2003, 12:17
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As 2Bdecided explained, this is only valid for cheap DACs. Good DACs filters the incoming jitter in such a way that the master clock is the DAC's one and not the CD Player's one.
The trick is that the DAC's master clock is allowed to drift very slowly in order to compensate for buffer variations. Ideally the buffer is 50 % full. If it becomes >50% full, the master clock is speeded up very smoothly in order to go back to 50%, and if it becomes less than 50% full, the clock is slowed down.

In conclusion, we still don't know which kind of players have a variable clock in order to lowpass the incoming jitter, and which ones directly slave themselves to the incoming stream, but we have another problem in addition, we don't even know if there is an audible difference between the two technologies .

By the way, I don't think that the time spent by a DAC to output audio after a digital stream is fed gives any useful indication. For example the Sony DTC 55ES is a DAT deck. The DAC takes from 0.5 to 1.0 seconds to output audio after a sample rate change. But the device produce an audible clic when it's done. This clic comes from an internal switch that turns the analog output on/off. The same clic is heard 4 seconds after the device is turned on, because a delay is set at startup, before the outputs are enabled, exacly like for many power amplifiers.
Thus the time took by a DAC to output sound when a digital stream is plugged on might depend on the delay setup for the analog output muting, that can have nothing to do with the time needed to synchronize with the incoming stream, or I'd rather say, that is setup long enough for the digital stream to be in sync long before the analog output is unmuted. How much long before is up to the engineer who designed the circuitry.
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- Pio2001   Anti-jitter RAM buffer in DACs   Aug 3 2003, 10:00
- - Patsoe   Since it's the cheapest thing, I can't ima...   Aug 3 2003, 19:58
- - F1Sushi   All CD players contain buffer memory between the E...   Aug 3 2003, 21:13
- - Halcyon   QUOTE As far as jitter at the DAC stage is concern...   Aug 4 2003, 09:36
- - 2Bdecided   Pio, I agree with the importance of your question...   Aug 4 2003, 11:27
- - F1Sushi   QUOTE (Pio2001 @ Aug 3 2003, 05:00 AM)So, do ...   Aug 4 2003, 12:53
- - F1Sushi   QUOTE (Halcyon @ Aug 4 2003, 04:36 AM)Does th...   Aug 4 2003, 13:44
- - Patsoe   Those are interesting side notes, F1Sushi. Could ...   Aug 4 2003, 14:05
- - F1Sushi   QUOTE (Patsoe @ Aug 4 2003, 09:05 AM)Those ar...   Aug 4 2003, 14:25
- - Patsoe   QUOTE (F1Sushi @ Aug 4 2003, 02:25 PM)http://...   Aug 4 2003, 14:44
- - Pio2001   Thanks, all of you for the answers. There was a pa...   Aug 4 2003, 14:54
- - F1Sushi   QUOTE (Patsoe @ Aug 4 2003, 09:44 AM)QUOTE As...   Aug 4 2003, 15:01
- - Pio2001   Sorry, I completely lost the link. It was an old s...   Aug 4 2003, 21:13
- - F1Sushi   QUOTE (Pio2001 @ Aug 4 2003, 04:13 PM)Sorry, ...   Aug 4 2003, 21:21
- - Pio2001   No sorry, there was no color, it was all about jit...   Aug 4 2003, 22:02
- - F1Sushi   QUOTE (Pio2001 @ Aug 4 2003, 05:02 PM)No sorr...   Aug 4 2003, 22:13
- - Halcyon   F1Sushi, thanks for the clarification! More ...   Aug 5 2003, 08:52
- - F1Sushi   QUOTE (F1Sushi @ Aug 4 2003, 04:21 PM)QUOTE (...   Aug 6 2003, 03:23
- - F1Sushi   QUOTE (Patsoe @ Aug 4 2003, 09:05 AM)Those ar...   Aug 6 2003, 04:10
- - Pio2001   QUOTE (F1Sushi @ Aug 6 2003, 05:23 AM)Could t...   Aug 6 2003, 12:49
- - TrNSZ   There is a device available from most high-end aud...   Aug 6 2003, 13:24
- - F1Sushi   QUOTE (TrNSZ @ Aug 6 2003, 08:24 AM)There is ...   Aug 6 2003, 14:17
- - F1Sushi   Found it - actually it's from Monarchy Audio, ...   Aug 6 2003, 14:36
- - Patsoe   Actually, from the description I'd suspect it ...   Aug 6 2003, 15:22
- - F1Sushi   QUOTE (Patsoe @ Aug 6 2003, 10:22 AM)Actually...   Aug 6 2003, 15:34
- - TrNSZ   To clarify on the "Monarchy Audio" DIP D...   Aug 6 2003, 15:57
- - F1Sushi   QUOTE (TrNSZ @ Aug 6 2003, 10:57 AM)To clarif...   Aug 6 2003, 16:20
- - 2Bdecided   In the current (September!) issue of Hi-Fi New...   Aug 6 2003, 16:32
- - F1Sushi   QUOTE (2Bdecided @ Aug 6 2003, 11:32 AM)The o...   Aug 6 2003, 16:42
- - Halcyon   2Bdecided, do you know of studies/measurements an...   Aug 6 2003, 19:25
- - F1Sushi   QUOTE (Halcyon @ Aug 6 2003, 02:25 PM)However...   Aug 6 2003, 19:44
- - Pio2001   You can always record an SPDIF output with an SB l...   Aug 6 2003, 21:19
- - Patsoe   QUOTE (F1Sushi @ Aug 6 2003, 03:34 PM)QUOTE (...   Aug 7 2003, 08:30
- - F1Sushi   My take on it is that the statement about "ab...   Aug 7 2003, 12:46
- - Patsoe   QUOTE (F1Sushi @ Aug 7 2003, 12:46 PM)Thought...   Aug 7 2003, 15:23
- - 2Bdecided   QUOTE (Patsoe @ Aug 7 2003, 02:23 PM)QUOTE (F...   Aug 7 2003, 15:36
- - F1Sushi   QUOTE (2Bdecided @ Aug 7 2003, 10:36 AM)QUOTE...   Aug 7 2003, 15:42
- - ChristianHJW   This thread confirms a couple of opinions i have s...   Aug 7 2003, 16:01
- - Patsoe   QUOTE (ChristianHJW @ Aug 7 2003, 04:01 PM).....   Aug 7 2003, 18:56
- - Halcyon   Shhh... don't tell them. It's reserved for...   Aug 7 2003, 20:09
- - F1Sushi   Just came across this link, which raises several t...   Aug 7 2003, 20:42
- - 2Bdecided   This thread should be in the FAQ! Cheers, Dav...   Aug 8 2003, 09:51
- - F1Sushi   Here's a Monarchy Audio DIP on a chip: http:/...   Aug 8 2003, 16:36
- - d_kay303   QUOTE (ChristianHJW @ Aug 7 2003, 07:01 AM)Th...   Aug 14 2003, 08:44
- - Patsoe   You're pointing out the exact reason why a two...   Aug 14 2003, 09:25
- - Pio2001   As 2Bdecided explained, this is only valid for che...   Aug 14 2003, 12:17


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