[dBe]

Just for sport, lets look at how a CD is actually made.  This is from: http://eil.com/explore/guide/cd_making.asp

A compact disc is constructed of 5 separate layers…

1.   First a thick, soft, clear plastic layer. This layer comprises the majority of the CD's thickness and weight. It serves two purposes. First, it protects the data layer from damage on the play side and Secondly it acts as a lens to focus the CD player's laser onto the data layer so it can more easily read the data (much the way lenses in spectacles help eyes focus on the words on a page).

2.   Next the data layer is where the music and any other information are stored. It's the layer that the CD player "reads" in order to create the music, graphics, etc. The data layer is molded or pressed into the top of the clear plastic layer. The data in the data layer is arranged in tracks that spiral like the grooves on a vinyl record (except CDs are read from the "inside out", the opposite of vinyl records).

3.   Now a reflective, metallic layer is located on top of the data layer. It allows the disc to function like a mirror, reflecting the CD player's laser back to the detector in the CD player after it reads the data layer It's this layer that gives the CD's play side a shiny appearance.

4.   A thin, hard protective layer is an ultra-thin plastic coating that is added to provide some protection for the reflective and data layers, while also forming a surface upon which the label information can be printed.

5.   Finally the label layer is printed on top of the protective layer. It contains the title, graphics, band and other information to identify the contents of the disc. (label side).

The aluminum reflective layer (or gold or silver in premium discs) is sputtered onto the topside of the data layer OR the bottom layer of the label surface depending upon process.

Back in the old semiconductor daze a fellow audiozany/coworker at Philips and I took CDs into qual at the FAB and look at several different aspects of how they were made.  The impetus for this were two different copies of the Bonnie Raitt CD "STREETLIGHTS".  They sounded widely different and we wanted to know why the disc sourced through Columbia Record Club (remember them?) sounded so crappy.  It was easy to see why.  The CRC disc had a sputtered layer that was wildly uneven with pits and barely reflective to a 780nm laser.  It would be a quagmire for a 405nm Blu-ray laser.  Not only was the sputtering uneven, the optical clarity of the two discs was different.  Not all polycarbonates are created equal and whever they use for the data layer looked different, too.  An electron microscope ia a wondeful thing.

This partially goes to show the differences between 'A' and 'X'.  even though they were from the same manufacturing batch - or at least out of the same master container - they sound different.  Almost everyone commented on the difference between the two with 'X' sounding marginally better than 'A'.

An additional observation.  About 5 years ago we did a cryo test on two copies of the Europen Columbia Jazz Reissue of Miles Davis "KIND OF BLUE".  There were completely different results from that cryo session.  The cryoed CD was measureably louder... not much, but louder all the same,  The spatial charactheristics were bigger, wider, deeper (what I call BWD) and the images were locked into place.  The biggest changes were the timbral aspects of the different instruments.  Coltrane and Adderly's saxes were markedly different and the big one for me was the sound of Bill Evan's piano.  Miles was... well Miles: all smoky and  expressive.  Those discs were a far cry from the discs that comprised the test.  I wish I still had access to the microscope.

Dave

[JerryM]

I'm interested in a description of the nature of differences, from early participants who heard a distinct difference.

I heard a significant difference between the discs. So much so that I pretty much botched the test.  

When Dave first started this super cool experiment, I apparently latched onto a "can you hear a difference?" mentality. The difference between disc A and disc B was so significant that I saw no reason to continue the test. 'Yes, Virginia, cryo makes a difference'.

I sent Dave my thoughts and Dave, sounding like some of my former college teachers, kindly replied (paraphrasing): "That's great, Jerry, but you botched the test."    In any case, here is a copy of what I sent Dave:

As I said earlier, I thought Disc A sounded best. Here's what I did:

I ripped three tracks from each disc to my hard drive; Coming Back To Life, What Do You Want From Me, and Marooned. I picked these three tracks because I know the songs like the back of my hand (and segregating three copies of the same disc was a far bigger feat than I had imagined). I ultimately used only Coming Back To Life, and I only really focused on Disc A and Disc B. There's such a significant difference between the two that I didn't really care what X sounded like because of the stark difference between A and B.

Disc A sounds better because it is fuller; the notes sound more "real to life". The separation of the sound stage is better, the bass is better, and the overall sound is just *better*. I could tell a difference in the first three seconds of the song, and confirm it again within 22 seconds. I've tried over and over again, from spots all over my room, and Disc A just sounds better. There is really no comparison between the two discs. Disc B sounds 'tinny'. It doesn't sound veiled or muffled, but it sounds half-full, like a copy of a copy that's been copied.


So, that was my take on the whole thing. 

Dave, thanks for sponsoring this super-cool experiment. Covering the cost of not only the original discs, but the shipping costs from point to point is only overshadowed by the amount of time and kindness you have invested in the project; from cryoing, to coordinating the shipping labels, to sharing your thoughts herein. You are a thoroughly bitchin' guy, and I appreciate you letting me take part in this. You Rock. 

Thanks again,

Jerry

[dBe]

Jerry, we all learned something here.  Hopefully we still are.  Later (this evening?) I will relate some experiential info and perhaps.... if I can find the source again... some info on cryo and optics.  Some of what I will relate is the experience of Mark Gaddis - a friend of mine that worked at Phillips Lab at Sandia Coroporation doing laser research for airborne laser weaponry.  He used to tell me about the unclassified stuff.  Unfortunately Mark passed away a few years ago, but he was an inspiration to me. 

Here is an excerpt from the DOD Employees of the Year in 2004:
"Mark W. Gaddis works as an electrical engineer in the laser division of the Air Force Research Laboratory at Kirtland Air Force Base, N.M. Because of imperfect bone structure, he has broken more than 20 bones and had more than 20 orthopedic operations. Despite his debilitating disease, osteogenesis imperfecta, he has designed and patented numerous systems in use throughout the laboratory and by Air Force and civilian law enforcement agencies. He is the lead engineer for helicopter illumination programs and the principal engineer supporting the laser systems in the Battlefield Optical Surveillance System."

Cool Dude Mark was.  He was an ardent music lover and we spent many hours together listening to and trying new pieces of gear, music formats etc.  Miss the guy.

Dave

[groovybassist]

Jerry:

I'll go back and listen to Coming to Life to see if I can hear what you heard. I'm not familiar with these songs, but your direction may help.

In terms of the test, I think listening to the rips vs. the discs takes your results out of the equation. May be completely valid, but outside the test protocol. I was concerned with the time gap changing discs - made it more tedious than I envisioned it would be.

Mike

[Mike B.]

I hope I am not crashing the party? I had a number of discs treated. I noticed slightly better focus and lower noise floor. The late Bob Crump didn't like cryogenics and had a comparison listening party with same disc cryoed and non cryo. He felt the cryo process destroyed important stage information. Same deal with his cabling. So I would encourage listeners to take note of any differences with respect to this aspect.

[dBe]

I hope I am not crashing the party? I had a number of discs treated. I noticed slightly better focus and lower noise floor. The late Bob Crump didn't like cryogenics and had a comparison listening party with same disc cryoed and non cryo. He felt the cryo process destroyed important stage information. Same deal with his cabling. So I would encourage listeners to take note of any differences with respect to this aspect.

I guess that as with all things audio YMMV.  This is especially true when it comes to fringe tweaks like crying CDs or ...   gasp!   - vinyl.

I have had mixed results with CD tweaks in general.  One weird deal that works pretty much every time is demagnetizing the CD before ripping or listening.  People always scream that there are no magnetic materials in a CD.  Perhaps, but I can pretty much guarantee that there are magnetic materials ON the CD.  We call them inks.  Another positive tweak is anti static treatments on the polycarbonate disc.  This is very noticeable out here in NM where humidity hovers around 12% most of the time.  Again, YMMV, but never dismiss the possibility that we don't know everything.  Photons are fragile critters.  Handle with care.

Dave

[dflee]

I believe I got the discs early on and portrayed my thoughts to Dave. While not being familiar with this music I randomly chose "A" to listen to all the way through and then picked out the parts I would concentrate on. I listened to the three with headphones first (my wife was asleep) and found "B" to be somewhat smoother. I guess I would say more laid back. I can't say that "B" was more musical but different in a way that the highs weren't so blatant. The Grado 125 is a little bright sounding and "A" and "X' certainly showed that quality, but I wasn't sure I could adjust to them. Later that same day I involved Shirley and we listened through the speakers. I had her write down her comments and I did the same while listening. We both came to the same conclusion that "B" was definitely different and was not as defined as the other two. While others here liked "X" better, we both thought "A" was a little bit better pronounced but we did not do a comparison between those two alone.
I can't thank Dave enough for the opportunity of participation in this study and for all he has done in executing an informal and fun as heck to keep up with tour. Great job!

Don

[dflee]

What the Sam Hill is goin on here??? You can't tell me that for all the time it took from start to finish that this is all the response
that can be generated. I kept up with the comments throughout the tour and thought afterward was going to be great. Dave stated he had some info to give out during the discussion and I for one am interested (is no one else). All the work, time and money spent by Dave deserves better than this from us or are we as pompous as the non-audiophile masses think we are?
I am surprised that someone or something (mail service) hadn't screwed them up before they actually did. Let's face it some people just don't give a crap for other's property. Lets not all sit around here with kid gloves afraid we may get our feelings hurt or heaven forbid we find our systems aren't as good as think they are. I know mine's not but I get a lot of enjoyment with what I do have and know if or when I am able, it will get better (includes being able to afford Dave's stuff). I have a lot of respect for Dave and others here and know we can do better in conveying our thoughts here.

Don (I know nothing) Fleenor

[SteveFord]

It's been so long I don't remember which one I picked as being different.
With the 20.7s I really kept going back and forth, back and forth but with the 1.7 system the differences were more noticeable.
I think it's because that system is much brighter sounding and the 20.7s were too gigundo for my living room which created a lot of difficulties for me.
I think the one I liked best was one of the non-cryo treated discs which would bring up the topic are all CDs created equal?
I'd say nope, even if they're CD-Rs.
I also know that I can easily spend the rest of my life without hearing that album again!
What do you want from me?  I want you to stop singing, enough, already!!!

[Pete Schumacher]

I'd love to see what happens to the data stream.  Are there differences in the 1s and 0s, the value of the digital words in any meaningful sense?

I can see where a botched optical layer would cause all kinds of read errors and software correction causing deviation from the source.  But does cryo treating actually reduce errors and thereby render a more accurate signal?

[dBe]

Its' all good.

The results of this process is on me.  I should have laid the tour out differently.  I made a couple of assumptions that were kinda dumb and the end of the CD Tour came with a whimper, not the Big Payoff.  I should have:

Selected the disc for the tour for excellence in recording quality, lack of compression, lack of digital processing, etc
Laid out very specific care and handling instructions including cleaning before each audition
Enforced a strict time limit.
and so on......

What we did learn:
The SQ of allegedly identical discs is different
Cryo did change the SQ and SC of the discs
People have different paradigms when it comes to how and what they listen to and for in the evaluation process
Surface quality is one requisite for reproduction excellence
Tours like this are very hard to make work... again: on me.

Cryo in optics is very important when we are dealing with photons and microscopic pits and bumps.  What cryo changes in the discs is the lattice structure of the materials used to make that disc.  The clarity of the material is partially determined by the orientation of the molecular structure of the lattice work.  This is why the new generation high resolution bench optics use cryogenically treated glass for higher resolution.  When crystal and molecular structures are optimally aligned there is less light refraction scatter through the medium.  What you get is a better read of the data.  Bits is bits.  It is how we get to the bits that determines the ultimate SQ of the disc.  Kind of like optically induced jitter.  Noise is noise.

One of the things that we have found recently is that getting the data on the discs is easy, but getting it off in a pristine manner is hard.  As decoders and software gets better so does to SQ of discs like the original recording of Sara K's GYPSY ALLEY.  I was there.  It was recorded it to 16 track 2" analog tape on a MCI JH24/16 and then mixed to 2 track on an Otari MTR10 1/2" machine.  It was the mastered to a Sony PCM1600 U-Matic 16 bit video recorder.  It sounds awesome when it is processed with today's' technology.  Truth be told about the PCM1600 is that the actual performance in the digital audio realm was 'about' 14 bits at best.  Processing the data error free is what gets the SQ to where we need to be.  Cryo "can" get it closer to the true recording, for whatever that is worth.  Today's digital processing is pretty amazing.

So, where does this leave us?

Dave

   

[SteveFord]

I'd think you'd want to have the discs cryo treated before you record onto them (if that's the correct terminology).
Perhaps the cryo treating something that has already been burned may not be the way to go.
Any thoughts?

[dBe]

I'd love to see what happens to the data stream.  Are there differences in the 1s and 0s, the value of the digital words in any meaningful sense?

I can see where a botched optical layer would cause all kinds of read errors and software correction causing deviation from the source.  But does cryo treating actually reduce errors and thereby render a more accurate signal?

Pete, I think that the differences we hear in discs are due to read errors.  Like I said: bits is bits.  Photons are funny little critters and are easily influenced by inducing energy fields as well as reflection and refraction.  It all physics.  We can bend a photon stream easier than we can bend an ion stream through magnetic or even static influences.  In the semiconductor industry we bend ion beams using magnetic fields to do the implant of atoms in the crystalline lattice that is a silicon wafer. 

Every chance that we have to make the process easier and to remove error correction from the equation should be addressed in order to get down to the bits.  Even the way the pit or land is formed can cause problems in the data stream.  We can change what the bit, but we can change how we read that bit. 

With CDs just like records Clean is King.  When I get a CD I clean it with isopropyl alcohol (good old IPA) and deionized water and then demag the disc using and old bulk tape eraser to demagnetize the inks before I rip it to the HDD.  That way I know that there is no mold release or anything else on that disc to degrade the data stream.  I know that is OCD territory, but I only have to do it one time to get the data right.  Makes a difference.  Physics works every time.  It's like gravity.  No voodoo or snake oil, just applied science in audio.

Man, I hope nobody throws the Gravity Switch 

Dave

[Triode Pete]

1's & 0's ???? ... some say not?!

An interesting read... http://www.audiostream.com/content/draft

[dBe]

1's & 0's ???? ... some say not?!

An interesting read... http://www.audiostream.com/content/draft

I am completely on board with what they are saying, Pete.  Digital is a conceptual construct at best.  It is impossible to produce instantaneous rise and fall times in a noiseless environment.  Just can't happen.  Seeing a digital signal as a square wave makes too much sense. The over and undershoot is noise, ie: distortion at best.  The thermal noise that the square waves ride upon are noise, distortion and jitter.  All of these components are read at some level by the system.  Not only that, but as word lengths and bit rates become  longer and higher respectively all of the aforementioned noise/distortion/jitter problems become even more problematic.  That is why there are a fairly large number of digital audio listeners that prefer non-over sampled 44.1 files for sheer musicality.  I still prefer to listen to my NOS 16 bit 44.1kHz Tranquility DAC for extended periods.  Sure, the new gen 32 bit 384KHz DACs are spectacular and quiet to listen to, but I think that the UHF well decoded noise signatures give an artificial sheen to the signal that is heard as detail.  It makes my teeth and my brain hurt after an extended listening session.  Sure, there is more data there... Perhaps too much.

I have been thinking about this for a long time.  Once again I come back to one of my overused old saws:  less is more.

YMMV

Dave

[Triode Pete]

Once again I come back to one of my overused old saws:  less is more.

YMMV

Dave

Dave,
We probably think alike... one of my favorite philosophies: "KISS - Keep It Simple, Stupid!"

Pete

[rollo]

  +1 here. That is why I use a dedicated 44.1 CDP. KISS baby. BTW I clean the CDs with lens cleaner, very affective.


charles

[dBe]

I thought that I would bring some of this up to date with some observations on the condition of each disc and provide some pictures of them.  Unfortunately we were burglarized and one of the things stolen was my camera.  I guess that for a while you will just have to take my word for the visual observations of the conditions of the discs.

Disc A shows the kind of surface scratches that discs receive when cycled in and put of an automobile single disc player.  Not pristine like I keep my discs, but very playable.

Disc B  shows a bit more of the same type of wear.  It also has 6 blobs of something that appears to be wax or a similar substance that range from about 1mm to 4mm across.  Not only that, but the larger blobs are thick enough to add mass to the disc.  It is confined to less than a quarter arc of the disc.  Rotational speeds of an audio CD vary from ~ 200 - 500 RPM.  Since CDs are read from inside out it is quite possible that the added mass of these blobs influenced the error correction of the read laser, especially in the first few tracks.

Disc X shows the least amount of wear and tear.  This is no surprise to me.  It consistently sounded better at the end of the Tour than the others.  The partial fingerprint on the rim of the disc probably was a non-issue.

Again, CD read quality is highly dependent upon optical quality (transparency) and reduced laser light scatter.  Scratches = light scatter through the disc which can induce read errors.

There is no wonder that the results deteriorated. 

Better luck next Tour I guess.

Dave