if you use a digital out on a cd player is there a sound difference between players? (2 Viewers)

[FrantzM]

HI

Jitter is an important issue, it does affect the sound significantly. Is it the main factor in the differences we hear between transports? I do not know and I do not think so. It is a human tendency to try to make things simple. The truth usually is more complicated. We are only beginning to explore digital audio and much is to learn.


Frantz

 

[Craig_Kg]

Let me repeat: unless the transport is so bad that it is introducing gross bit errors, the ONLY sonic differences that there can be between transports are ENTIRELY due to jitter.

Digital is subtle but simple.

 

[Kevin C Brown]

Craig- Sorry, but I don't buy that either. There's error correction, defect navigation, anti-aliasing filters, how good the DACs are, vibration isolation, etc. Just read any CD player review in Stereophile.

Jitter is a substantial part, but the "ONLY" determinant of sonic quality? Naagh.

 

[Lee Scoggins]

Jitter is a substantial part, but the "ONLY" determinant of sonic quality? Naagh.

I agree if you are talking about using it for more than a transport. In those cases, powersupply and output filters and circuit design all make a difference.

 

[Craig_Kg]

I thought this thread was about using the CD player as a transport only (digital out)?????????
My comment was made in that context. I did say "between transports" :frowning:

If you are using the analog outputs, well then of course, jitter is only one aspect affecting sonic performance.

 

[KeithH]

Whether one believes it or not, it seems that the high-end manufacturers go beyond minimizing jitter in designing a quality transport. They talk about quality power supplies, isolation, etc. Food for thought.

 

[Craig_Kg]

For a transport, all the p/s noise supression, etc does is reduce jitter.

The only other thing to consider between transports is the user interface feature set (remote, track selection, cd text, etc).

 

[RobWil]

I did a test yesterday using an HK HD7600II cd player connected to an HK AVR520. The cd player has analog, digital coax and optical audio outputs so I hooked up all 3 at once and switched back and forth with the OSD. I was using Monster Interlink 400's for the analog, a Monster THX I100DCX for the digital coax and an Interlink Lightspeed 100 for the optical, all 1m length. The optical and analog settings were right next to each other on the OSD so that was a very easy test, but the coax was a little trickier but basically I could tell no difference at all between the three. Then I looked at the analog audio cables connecting my sattelite receiver and noticed they were Interlink CD's. I have no idea when I bought these or where they came from but I decided to try these in place of the Interlink 400's and do the same test.
Well I was amazed at what I heard and could easily tell the difference in these compared to the coax and optical outputs. The music from this cable/mode sounded much fuller and the bass was much more musical sounding and very tight. The others sounded hollow in comparison and the bass boomy and slightly muddled. Needless to say I left these cables on the cd player and ditched the other ones.
Bottom line is that I think it partly depends on the quality of the DAC's as well as the interconnects being used. A strong selling point of my cd player (5 yrs old though) was it's DAC's (Linear, Pulse Width Modulated Bit Stream, clock rate 33.8688MHz, per the user manual). I am really not sure how this rates with the DAC's in todays receivers but keep in mind that I did not hear a difference until I switched analog interconnects. It makes me wonder what the difference would have been if I'd had some really serious analog interconnects. Or maybe I just had really shabby digital interconnects??

 

[Kevin C Brown]

Craig- Do you know what EAC is? If all transports were the same, we wouldn't need eac... (Exact Audio Copy...)

 

[Craig_Kg]

EAC is needed because the CDROM drives are not guaranteed to resync to the same spot with damaged media or notice the damaged media at all - this is especially prevalent with multispeed CDROM ripping (which is how everyone normally does it).

With a 'normal' CD transport and decent media, these are not issues.

 

[John Sully]

Oh joy, another jitter debate.

Basically it comes down to this: jitter is a problem with cheap DAC's which derive their clock from the incoming signal. But it is very easy to design a DAC which uses a simple shift register to ensure that the clock is accurate and not subject to drift (jitter). For an existence proof check out the patents which Analog Devices holds on this method. There is no need for a "jitter jail" or a huge buffer or any of the other high end solutions to jitter. You just need a DAC which does *not* derive its clock from the incoming bitstream.

The funny thing is that I've seen some high end designers claim that the solution outlined in the Analog Devices patents to be suboptimal because it "doesn't use the original bitstream". This is pure hokum. If the bits are extracted correctly from the bitstream and each sample is converted at the proper time interval after the previous sample the analog output of the DAC should be a reasonably (given the limitations of bandwidth, S/N ratio and distortion added in the A/D process) identical copy of the original analog input. PERIOD. END OF DISSERTATION.

Only a piece of crap DAC will be affected by jitter.

 

[Lee Scoggins]

Only a piece of crap DAC will be affected by jitter.

I am sorry but this had not been my experience in the recording studio.

Case in point: the Alessis greatly benefits from adding in a Lucid Audio masterclock device which lower jitter an order of magnitude.

At Chesky Records, we hear differences in DACs when we edit and the lower jitter DACs always are better.

There are several issues beyond just what is on the DAC - there are places on the circuit design that are affected.

Just a differing point of view.

 

[Kevin C Brown]

If the bits are extracted correctly from the bitstream...

EAC exists because not all drives are as accurate as you'd like in terms of simply getting that data off the disc... Data drives in PCs (which in fact, a lot of consumer electronics products use nowadays), and consumer drives too. Obviosuly, you can't use EAC for a CD player in your stereo system, but the same principals apply.

 

[Craig_Kg]

Lee Scoggins, John Kotches, what do you think of Kevin's assertion that most transports will corrupt the PCM values from that stored on the CD (forget the timing for the moment)?

I disagree, of course. This is the area where CD is very good (there is a LOT of error correction built into the redbook format).

 

[Ron Economos]

I've done some testing with the Pioneer DV-47Ai 1394
digital output. I can capture the PCM bitstream to
a file and compare the results. I get the same exact
bits every time I capture a track. I also get
the same exact bits from a CD-R copy of the original.

This is not speculation. I've actually performed these
tests and checked the bitstreams. Given that 1394
can deliver a jitter free stream, I have to conclude
that bits are bits and 1394 based transports can all
perform exactly the same as long as the error correction
is not overwhelmed (leaving the differences between
transports to how well they deal with dirty, scratched
or damaged discs).

Ron

 

[Lee Scoggins]

what do you think of Kevin's assertion that most transports will corrupt the PCM values from that stored on the CD

In terms of ones and zeros (pit and land) I would agree that separate transports generally get this right. I would not go as far to suggest that the time code is perfectly matched up for playback, however, which has been my point all along.

 

[Kevin C Brown]

most transports will corrupt the PCM values

I like how you twist what I said. There *are* differences between transports in terms of the digital bitstream that is pulled off the disc. And you completely ignored how quality vs crappy transports handle defect navigation and error correction (the latter which also occurs in the digital domain). You also neglect to address reliablity, which will also be a key difference.

 

[Craig_Kg]

How am I distorting what you say Kevin? I was just stating explicitly what you imply - if there are digital differences in the data values, then the PCM is being corrupted.

With decent media, almost ANY transport these days will extract the PCM from a redbook CD with 100% accuracy (you are saying they won't). I am including the error correction that takes place in the digital domain as this is part of the redbook spec. This ensures that any sonic difference will be ENTIRELY due to jitter.

Lee, I did say "forget the timing for the moment"

As for reliability, we are talking about sonic performance.

 

[Kevin C Brown]

A CD player transport includes at least the following: a laser to illuminate the pits in the disc, a detector to be able to judge if it's a "hill" or "valley" we are looking at, optics in between the disc and detector to get that reflected light from the disc to the detector, and a motor to spin the disc such that subsequent pits can be read.

I guess there can be absolutely no difference in how any of those parts of a transport operate, *and* interact together, whether it's poor quality or good quality. There's absolutely no threshold for combinations of parts where even if it's 1 in a thousand or 1 in a million, where a 1 is misread to be a 0. Bits is bits, and you always gets exactly perfectly what is on the disc output from the players digital outputs. Come on... Do you really think that even other than jitter, you're going to get the same digital stream out of a $49 KMart player as compared to something that costs a few hundred or a few thousand dollars?

Error correction... Among other things, error correction interpolates (or even extrapolates) what the unknown bits would be in between known samples. Even the best error correction on earth cannot tell you what the original bits were, just something that is an approximation of the information as it exists on the disc. So, cheap players can have poor implementations of error correction, and better quality players can have better error correction.

Reliability. I have had 1 CD and 1 DVD player as CD players die in my lifetime. At least in the 2 cases I've personally experienced, the problem is initially manifested by a "skipping" CD. But I also know darn well, that before that point has happened, the sound quality has been compromised. Not just jitter. Transport related perturbations of that digital stream.

And even now I notice you say...

the ONLY sonic differences that there can be between transports are ENTIRELY due to jitter

Hopefully John K (or Manoj from DVD Etc) will chime in on this, because both of those guys know more about this than either me or you.

 

[John Sully]

As stated previously there is a large amount of error correction built into the Redbook spec. This error correction is based on Reed-Solomon codes and is capable of exactly reconstructing a heavily degraded bitstream exactly. A fall back strategy is to interpolate missing samples if the data cannot be reconstructed exactly via the error correction data contained on the disc. Finally a player will mute it's output if there is too much missing data.

One more thing to think about: if it is not possible to extract an exact copy of the bits on the CD it would not be possible to use CD's as a data storage mechanism. Yet CD's (including CD-R and CD-R/W) are used extensively and very successfully used as a data storage mechanism.

Finally, the skipping which Kevin noticed is generally due to wear in the parts of the laser tracking mechanism which of course will result in the eventual total failure of the drive's ability to extract a bitstream.