Basic (hopefully) digital signal question

admin_exported

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Hi,

Here two cases:

#1- Let say I’m using my Cambridge 650BD as source using the optical output plugged in my future buy, the Rega DAC (with a Brio-R).

#2- Instead of the 650BD, I plug other CD players between 200$ and 1000$ also plugged through optical in the Rega DAC (with Brio-R).

My understanding is, since I’m using digital signal in all cases, at the end the sound coming of the speaker would be the same. Or I got it all wrong?

*******

Also, what would be the usage for the digital output on the Rega DAC? To plug into another crazier big buck Amp/DAC system???

Thanks!
 

MajorFubar

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All half-decent players should sound the same when connected to the same DAC. However there are people who believe that certain CD transports do a better job of extracting the data from the CD than others. Though that's another one of those subjective views which creates 'debates'*

* = heated arguments.
 
If that were the case then all CD players would have cheap transports and increasingly bettter DACs as price increased.

Simply put, the integrity of the output from the transport depends on its quality and, for example, its isolation from vibration, much as a turntable. If, say, a signal with more jitter arrived at the DAC, there would be limits to what the DAC can do to eliminate its effects. So the better the transport the better the sound, with the same DAC. If only it were as simple as you hope!

Sorry, can't help re the digital out, but its probably obvious and I just can't think why right now!
 

The_Lhc

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nopiano said:
Sorry, can't help re the digital out, but its probably obvious and I just can't think why right now!

Some (stereo) DACs will pass through a multi-channel signal when detected, so the digital out could be connected to an AV amp for surround purposes, without having to split the digital output from the source (a universal disc player for example).
 
Thanks, Lhc, that was what completely escaped me.

It seems I came at this from the opposite angle to MF (whose post I hadn't seen first), so to illustrate my point, consider this recent news release for the Cyrus CD transport:-

http://www.whathifi.com/news/manchester-show-2011-cyrus-debuts-cd-transport

It says, that "The CD Transport can, however, be upgraded to the twin-transformer design and full CDXTSE2 if/when you want." Obviously if it made no difference to the digits, no-one would need the better model. And the basic one is already way more than half decent.
 
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Anonymous

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I see. All these answers make sense to me now.

Thanks for your help!
 

dannycanham

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The 0s and 1s don't change but you have timing errors.

You have two clocks creating timing jitter and two converters of the signal from electrical to light creating timing errors.

1) You have jitter going into the dac produced by timing errors from the player.

2) You have internal jitter produced by the dac.

Obviously not all the improvements in a better player would lead to an improvement in the timing of the signal leaving it. But you would hope some of them do. This wuld improve 1).

The actual audible difference is not particularly clear or always audible. I'd dum it down to high frequency clarity and organisation amongst instruments.

I woud agree with the opinions on the test on this link. Except where they use words like "great" I would use a word like "audible".

http://www.jitter.de/english/soundfr.html
 

dannycanham

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Better players create systems that are less prone to read errors when spinning discs.

I would argue that these upgrades largely don't help. They just increase the cost of the product. The main reason being that even cheap players don't have problems reading the data off disks in most circumstances.
 

MajorFubar

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Another use for a digital output from a DAC would be to pass the digital signal to a digital recorder, such as a CD burner or Minidisc recorder.
 
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Anonymous

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Dan Turner said:
dannycanham said:
I woud agree with the opinions on the test on this link. Except where they use words like "great" I would use a word like "audible".

http://www.jitter.de/english/soundfr.html

Great link - very interesting. glad someone has finally tested this objectively and proven the phenomenon 'jitter'

Not to detract from the the link which is worth a read, jitter is a well understood phenomenon in the engineering field since the early days of digital transmission - it is just the audiophile world that seems to have difficulty grasping it. There are disagreements at which level jitter becomes audible, and as the parameter is difficult to measure and to compare (manufacturers can report peak, RMS, average, 1SD) then it gets brushed under the carpet. The level of audible jitter seems on depend on the type of jitter as well - whether it is correlated to the program material (more audible) or random (less audible).

In the final analysis, if two digital sources really do sound different, then absent bit errors, the only other possible explanation is jitter.
 

dannycanham

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You are right it is very difficult to grasp in the audio world. Differences in audio are often described as vast/night and day/like listening to a new player, which doesn't help when comparing one design problem/improvement to a different design problem/improvement. The people who have the opportunity to do audible tests on jitter are often selling something and have a vested interest in promoting a certain idea. It is rare for everyday hobbyists to listen to very similar systems with jitter measurements being one of the few changes. We have no single scale for jitter measured and we have no scale for describing the audible effects of jitter either. Jitter also isn't just one type with one audible outcome.

I upgraded the clock on the rDac. The difference was more definition/solidity/organisation to complex highish frequency sounds such as maracas/tambourines or to each individual clapping in an audiences applause, as well as musicians coming across as more skilled. I would attribute the change to reduced internal jitter as the rDac is known to have middling levels of internal jitter for a DAC, no other upgrades were made at the time, and the rDacs USB input has been measured to be good at negating the effects of much of the jitter entering the DAC. The descriptions in the link are very close to my experience, but without as large a scale of feeling towards the improvements.

When listening to many different sources the effects of jitter have never been clear due to the many different characteristics of each source.

Similar to a camera with a better lens. Pictures may come out with sharper focus over a larger range or be less prone to vibration based blur. The actual image improvement for the human viewer is difficult to quantify. It takes more than a good lens to create a good camera, more than a slightly softer lens to create a bad one and it isn’t easy to compare lenses when each are tested on a different camera.
 
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Anonymous

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dannycanham said:
I woud agree with the opinions on the test on this link. Except where they use words like "great" I would use a word like "audible".

http://www.jitter.de/english/soundfr.html

As mention earlier, it is indded a great link. Thanks!!!

Compare to other technical stuff I have been reading, this one does provide good technical info for those who likes it and a good short and sweet "popular" explanation by reading only the intro and conclusion. Thank!
 
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Anonymous

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dannycanham said:
where they use words like "great" I would use a word like "audible"
...and where they use words like "everybody" I would use "all of us".

:silenced:
 

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