Lossless Files Vs CD's

My understanding is that if a CD is in good physical condition, the main reason why it might sound inferior to playback of a bit-perfect computer file is NOT errors that the player can't correct on the fly in a bit-perfect manner, which would therefore require inexact interpolation. My understanding, based on numerous references I have seen in the past, is that for a disk that is in good condition that will happen rarely during the playing of a disk, and not at all in many or most cases.

The main reason that real-time CD playback may provide inferior results is that electrical noise generated by the servo mechanisms and circuitry in the transport part of the player, as it tracks the disk, may couple into unrelated downstream circuitry in the player, causing jitter in the D/A conversion process, and/or effects on the analog signal path. The degree to which that occurs will be dependent on the design of the particular player, of course, as well as on the condition of the disk.

From this Wikipedia writeup:

Reed–Solomon coding is a key component of the compact disc.... In the CD, two layers of Reed–Solomon coding separated by a 28-way convolutional interleaver yields a scheme called Cross-Interleaved Reed Solomon Coding (CIRC).... The result is a CIRC that can completely correct error bursts up to 4000 bits, or about 2.5 mm on the disc surface. This code is so strong that most CD playback errors are almost certainly caused by tracking errors that cause the laser to jump track, not by uncorrectable error bursts.

Note that the term "error correction," as properly defined in this context, refers to bit-perfect correction. "Error interpolation" is the term used to refer to the less than bit-perfect approximation that can occur (rarely) when bit-perfect correction fails.

And from a post by Kirkus in this Audiogon thread:

CD players, transports, and DACs are a menagerie of true mixed-signal design problems, and there are a lot of different noise sources living in close proximity with suceptible circuit nodes. One oft-overlooked source is crosstalk from the disc servomechanism into other parts of the machine . . . analog circuitry, S/PDIF transmitters, PLL clock, etc., which can be dependent on the condition of the disc.... One would be suprised at some of the nasty things that sometimes come up out of the noise floor when the focus and tracking servos suddenly have to work really hard to read the disc.

Regards,
-- Al

07-11-12: Kijanki
>2.5mm scratches along the disk are very likely causing interpolation of data.

I believe that is generally true only if the scratch exceeds that length in the direction that is followed by the spiral track. A narrow scratch in a radial direction, for example, could extend across the entire diameter of the disk without causing data errors, unless it is deep enough to allow air to enter and cause deterioration of areas that are adjacent to the scratch.

Best regards,
-- Al

07-11-12: Dhl93449
Well, if that were completely true, tweaks like Lightstop (green dye around outer edge) would have no impact on sound quality. But many have observed they do impact sound (including myself).

All of the references that I have seen over the years that I consider to be credible, including among many others the ones I quoted and linked to earlier and Steve's comment above, are consistent with the conclusion that any benefits those kinds of tweaks might provide result from improvements in trackability, resulting in less noise being coupled from the servo mechanisms into other circuitry in the player. Not from a reduction in uncorrectable errors.

Best regards,
-- Al

05-26-14: Dvavc
The point here is that you loosing the quality of the sound (SQ) right there when you ripping/converting PCM files from CD in to WAV on your comp.

FWIW, I see no technical basis for that contention (assuming the rip is done with software that assures bit perfect results), and it is certainly not proven by the experiment you described earlier, as I had indicated in my previous post. Nor am I aware of any other reported experiment supporting that contention.

Regards,
-- Al

05-22-14: Dvavc
But of course ripped files are sound inferior compared to it's sourced CD.... Let's do very simple test and compare apples to apples, that you can witness said difference for yourself.... Now, using any software of your choice, let’s rip any file(s) from any CD (your choice) to the HDD or SSD of said computer (BTW, SSD do sound better than HDD, but it doesn’t matter for this test). When rip is done, insert headphones directly in to the computer audio out jack, on the back of the comp and compare the sound of CD played back from the same CD ROM and ripped file(s), played trough the same computer playback/rip software. Don’t use different softs for playing back file(s) and CD, because different softs will sound differently.... If you done everything right, you should easily hear that ripped files have a little bit less of everything i.e. less micro musical nuances, less airiness, different voice tembres, etc., compared to CD. It is similar to Xerox copy, i.e. everything looks the same (the writing is still there :~)) but a little bit less of everything, less clarity, less contrast etc. I wish I knew what causing it and how to fix it, but unfortunately I don't. (((

Seconding and expanding on the point Kijanki made above about ambient electrical noise, playing back a file stored on the computer's hard drive figures to result in differences in electrical noise that is coupled from the computer's digital circuitry and its power supply into the D/A converter circuit on the computer's sound card or motherboard, compared to playback of a CD by that computer. That in turn will result in differences in timing jitter occurring in the D/A conversion process, which I suspect is the main reason for the differences you heard in making the comparison you described.

What is being discussed in this thread, however, are differences between playback of a CD in a separate CD transport or player and playback of a computer file via a digital output of the computer (e.g., USB or S/PDIF or Ethernet or Wifi). The effects of noise coupling into the computer's D/A converter circuit has no relevance to those situations.

Excellent input from Lewinski, IMO.

Regards,
-- Al

Kijanki and Pokey, thanks very much for your kind comments. And I certainly second Pokey's comment about Kijanki and Steve.

Best,
-- Al

05-28-14: Dvavc
To: Audioengr, Pokey77 and Almarg: Guys, I think i know whats going on here,;~) but I won't be jumping the guns until i see Steeven at The show and listen to his "bit perfect rip" on his server and than we'll see if somebody really need a hearing specialist or something else is going on because of somebody's involvement with the industry....

As a point of information regarding this comment, I do not now nor have I ever had any affiliation or connection with any individual or organization in the audio industry. I do not own and have never heard any of Steve's products. I am a retired EE with 33 years of experience designing and managing design of advanced digital and analog circuits for defense electronics, primarily airborne radar systems.

I also have never met or had any communication with Steve, Kijanki, or Pokey, aside from posts in threads at this forum.

Regards,
-- Al

06-01-14: Audioengr
His assertion is that ripping CDs is a flawed process because he hears a difference when playing back the same track on a PC or Mac using first the CDROM as a transport and then with the ripped track playing back from hard disk.

The problem with this comparison is that it is NOT apples to apples. Because the playback hardware paths in the computer for CDROM and memory/disk playback are entirely different and they actually use two different clocks, I would expect these to sound very different. This has nothing to do with the rip quality.

I agree completely, Steve. The experimental methodology he described in his first post in this thread (dated 5-22-14), the validity of which I disputed in my subsequent response, cannot distinguish between effects occurring during the ripping process and effects occurring during the playback process. Yet he attributes the differences he perceived to the ripping process, even though (as we've both explained) it is entirely expectable and technically explainable that differences will be introduced during playback, and entirely unexpectable and technically inexplicable that differences will be introduced during a properly implemented rip.

Regards,
-- Al

Dvavc, Steve and I have both indicated multiple times in our earlier posts that the methodology you have used in your comparisons of CD playback with your computer vs. file playback with your computer, to quote one of my statements:

... cannot distinguish between effects occurring during the ripping process and effects occurring during the playback process. Yet he attributes the differences he perceived to the ripping process, even though (as we've both explained) it is entirely expectable and technically explainable that differences will be introduced during playback, and entirely unexpectable and technically inexplicable that differences will be introduced during a properly implemented rip.

In other words, that comparison is not apples to apples, as you continue to claim. Somehow that point seems to not be getting across.

Regards,
-- Al