It's pretty easy to suss these sort of things out - you deliberately raise the level of stress on the electronics, until even the deaf as a post objectivists can pick up that there is a problem, 🙂, say with the CD rough up the playing side with coarse sandpaper so the laser is struggling constantly, and shave the sides of the hole to make it even more eccentric while spinning - this way you attune to the audible problems being caused, because they're now so obvious. Then, slowly fix the "problems", little by little, until the audible artifacts go away - you now have a handle on the dynamics of the interaction that is causing sound degradation - and hopefully can fix it!
With subsequent recordings, they may have used different quality blanks, bringing yet another variable into the equation. This is the sort of thing that needs to be done extremely rigorously, repeatedly, until precisely the mechanism causing problems is understood - the "digital getting worse" does not compute!
With subsequent recordings, they may have used different quality blanks, bringing yet another variable into the equation. This is the sort of thing that needs to be done extremely rigorously, repeatedly, until precisely the mechanism causing problems is understood - the "digital getting worse" does not compute!
It could be worst , he could be an Alien polymer scientist with a 5 watt toob Amp who happens to specialize in optical anal probing .... 😛
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I have a test disc with different generations up to 200 i think , the original generation is the reference , Better ...?
Yeah, I have noticed there are some people who associate plastics material with naughtiness ... 😉
As an aside, I'm having fun with our Yamaha keyboard - at the moment it's cycling a MIDI of Chopin's Fantasy Impromptu at full bore, pretty damn good I must say - it passes the "gosh, that's a good pianist playing in that house!" test, 😛 ...
As an aside, I'm having fun with our Yamaha keyboard - at the moment it's cycling a MIDI of Chopin's Fantasy Impromptu at full bore, pretty damn good I must say - it passes the "gosh, that's a good pianist playing in that house!" test, 😛 ...
So, do I take it that you don't have any reference showing that any of this has any audible effect? Nor any explanation of how any of that can matter if data recovery is essentially perfect? Not to mention the relevance of thin films of conjugated polymers to thick layers of molded polycarbonate?
Google fishing is a pretty poor way of trying to establish a valid technical argument.
It's frustrating when you don't get gullible and ignorant people for an audience, but hang in there, John, they're around somewhere. 😀
I do and it was published in stereophile pertaining the spatial filter product. At the time I was working in IL for Amoco laser. Amoco bought a patent for diode pumping solid state lasers we had authored at the Jet Propulsion Laboratory. They started the company with that patent. I mention this because there was some kick *** equipment there and that is what we used to make the measurements in the article. I have no reason to hand wave and the product worked. In fact several high end audio companies used the filter OEM. This was '91, '92, '93 - around that time. This was the time I started manufacturing the fiber optic links. remember , no one (audio customers) really knew what fiber optics was back then. pre awful lucent commercials.
As far as optical properties in thin-film or bulk. Really? effects on the quantum level are dependent on material thickness/ About the only thing that happens is the thin-film, up to a certain thickness will follow the mechanical properties of the bulk host, i.e CTE, compliance etc. Glass is regularly deposited on high power laser diode facets for mirrors. If I made a bulk antifrelection composite inches in nominal length, it would perform the same as a thin-film, baring transmission loss (absorption) as long at the thicknesses were some integer of the wavelength in question.
As far as optical properties in thin-film or bulk. Really? effects on the quantum level are dependent on material thickness/ About the only thing that happens is the thin-film, up to a certain thickness will follow the mechanical properties of the bulk host, i.e CTE, compliance etc. Glass is regularly deposited on high power laser diode facets for mirrors. If I made a bulk antifrelection composite inches in nominal length, it would perform the same as a thin-film, baring transmission loss (absorption) as long at the thicknesses were some integer of the wavelength in question.
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Yes, I am one of the 'gullible' guys in audio. I actually believe in what my colleagues and I hear, and I act on it. That is how we make audio products. Seems to work, OK.
I see that all the time, at meetings. 7 researchers throwing out advice on a build or having to know every last detail. sometimes you just have to build it with a basic understanding and see what happens because nothing ever goes together as planned. it a fine line, too much thinking doesn't work, not enough doesn't either. I guess that's why there are thinkers and why there are builders.
It helps immensely if you know, from personal experience, that something is attainable. If the theory doesn't get you there, then dogged experimenting, in unconventional ways, will ultimately bring forth a positive outcome - steady refinement over time, of the process of ensuring the right result every time, adds to the "knowledge base" of understanding of "what's going on" - it's a journey ... 🙂
You just don't get it do you Frank 🙄
Hewlett-Packard uses the scientist and his perfect 1Khz whistle to calibrate their test equipment, His ears are insured with Lloyd's of London, traps his own bass and can Bias his 5 watt power tubes to within 1mV ... by ear.
He is worthy .....
Hewlett-Packard uses the scientist and his perfect 1Khz whistle to calibrate their test equipment, His ears are insured with Lloyd's of London, traps his own bass and can Bias his 5 watt power tubes to within 1mV ... by ear.
He is worthy .....
Optical discs and magnetism
I was unfortunately sucked into researching this one myself when I was the Dir. of Engineering at AMI (CD/DVD manufacturer). Some of my more high-end customers heard this and asked me to prove our CDs didn't need demagnetizing or green edges. We used two extremely sensitive mapping double-pass birefringence testers, a Dr. Schenk Prometeus (http://www.drschenk.com/uploads/media/prometeusmt_200_02.pdf) and a Datarius Optical Tester (DaTARIUS - optical testing - Optical Analyzer) which not only show magnitude of birefringence, but also the direction. We tested discs molded using standard optical disc grade PC of both Bayer Makrolon and Sabic (GE) Lexan.
After a lot of testing we found zero correlation between the application of magnetism before and after testing, using very strong, 1cm square neodymium magnets. Not only that but the jitter and resulting error rates were identical to within the repeatability of our CD CATS SA3 testers on all CD samples so treated, before and after. We concluded there was no interaction between the polycarbonate substrate and applied magnetic fields. As far as adding to the "background optical noise," if present it would have shown up as a degradation in peak jitter (all optical aberrations are measured by the jitter they induce), and there was none we could measure.
Perhaps with a cheap grade of polycarbonate with high percentage of metallic salts or other contaminants different results could be seen.
Oh, and the green pen edge application: the same. Zero change in jitter or error rates to within the repeatability of the tester. At the same time we had customers swearing they could hear a difference, and maybe their players were so different from standard playback units that they were sensitive to off-axis illumination of the optics? In that case the player would be at fault and out of specification. In mass production one does not make intentionally out-of-spec discs to compensate for a few out-of-spec players.
Just part of my 20 years of optical disc experience, yours may vary.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
1st on the internet
I was unfortunately sucked into researching this one myself when I was the Dir. of Engineering at AMI (CD/DVD manufacturer). Some of my more high-end customers heard this and asked me to prove our CDs didn't need demagnetizing or green edges. We used two extremely sensitive mapping double-pass birefringence testers, a Dr. Schenk Prometeus (http://www.drschenk.com/uploads/media/prometeusmt_200_02.pdf) and a Datarius Optical Tester (DaTARIUS - optical testing - Optical Analyzer) which not only show magnitude of birefringence, but also the direction. We tested discs molded using standard optical disc grade PC of both Bayer Makrolon and Sabic (GE) Lexan.
After a lot of testing we found zero correlation between the application of magnetism before and after testing, using very strong, 1cm square neodymium magnets. Not only that but the jitter and resulting error rates were identical to within the repeatability of our CD CATS SA3 testers on all CD samples so treated, before and after. We concluded there was no interaction between the polycarbonate substrate and applied magnetic fields. As far as adding to the "background optical noise," if present it would have shown up as a degradation in peak jitter (all optical aberrations are measured by the jitter they induce), and there was none we could measure.
Perhaps with a cheap grade of polycarbonate with high percentage of metallic salts or other contaminants different results could be seen.
Oh, and the green pen edge application: the same. Zero change in jitter or error rates to within the repeatability of the tester. At the same time we had customers swearing they could hear a difference, and maybe their players were so different from standard playback units that they were sensitive to off-axis illumination of the optics? In that case the player would be at fault and out of specification. In mass production one does not make intentionally out-of-spec discs to compensate for a few out-of-spec players.
Just part of my 20 years of optical disc experience, yours may vary.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
1st on the internet
CDs
When I wrote my reply about the magnetic interaction with CDs I assumed due to your use of the term CD, you were referring to replicated CDs which are injection molded with the data molded directly in from the stamper present in the mold cavity. The only spinning is to distribute and level the top-side protective lacquer.
In your current post it sounds like you are referring more to CD-Rs, which have other layers and processes performed after the substrate is molded?
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
1st on the internet
When I wrote my reply about the magnetic interaction with CDs I assumed due to your use of the term CD, you were referring to replicated CDs which are injection molded with the data molded directly in from the stamper present in the mold cavity. The only spinning is to distribute and level the top-side protective lacquer.
In your current post it sounds like you are referring more to CD-Rs, which have other layers and processes performed after the substrate is molded?
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
1st on the internet
CD-Rs
There is zero difference between the potential tracking error of a molded, replicated CD and that of a CD-R. CD-Rs as bought are pre-grooved. The tracking servo follows the pre-groove molded into the CD-R, just as in a replicated CD the tracking servo follows the pit track. In both cases the physical features being followed are molded into the substrate from features present on the stamper in the mold cavity. The eccentricity is dependent on mold design and manufacture, mold half alignment on the IMM and other factors.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.ortg
1st on the internet
There is zero difference between the potential tracking error of a molded, replicated CD and that of a CD-R. CD-Rs as bought are pre-grooved. The tracking servo follows the pre-groove molded into the CD-R, just as in a replicated CD the tracking servo follows the pit track. In both cases the physical features being followed are molded into the substrate from features present on the stamper in the mold cavity. The eccentricity is dependent on mold design and manufacture, mold half alignment on the IMM and other factors.
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.ortg
1st on the internet
Howie, did you look at the BER as a consequence of optical amplitude noise or optical phase modulation? Assuming optimal sampling?
On a complete sidetrack, quite an interesting piece, for those who may be unaware: Planet Analog - Kendall Castor-Perry - Just Add A Transistor: Clipping Me Softly ...
CD BER
The BER, or BLER as it is called in CDs is an expression of the errors at the C1 stage after squaring and limiting. As a result it's relationship to variability in the optical path, whether amplitude or timing is dependent on the amplitude of the recovered pit track, specifically the longest, highest RMS value pits called I11s (11 times the basic EFM clock rate). If, due to poor mastering or molding, the I11 amplitude is low, then errors (or jitter if you will) will rise as a function of all other variables. In CD testing, there is not a separate variable or measurement called optical amplitude noise, but the equivalent, I11 amplitude and delta is tested, so any variability which would impact BLER is recorded. Variations in I11 amplitude which exceed stage 1 spec are called Drop Outs, and Drop Out Length or DOL is part of the Philips Yellow-Book CD-ROM specification along with I11 amplitude, double-pass birefringence (optical phase modulation), and a metric ****-ton of other parameters. Many a day...hell year of my life went into diagnosing and correcting deviation of these parameters of the now-obsolete media format...
dang! the forum deleted my totally called-for cussing!
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
1st on the internet
The BER, or BLER as it is called in CDs is an expression of the errors at the C1 stage after squaring and limiting. As a result it's relationship to variability in the optical path, whether amplitude or timing is dependent on the amplitude of the recovered pit track, specifically the longest, highest RMS value pits called I11s (11 times the basic EFM clock rate). If, due to poor mastering or molding, the I11 amplitude is low, then errors (or jitter if you will) will rise as a function of all other variables. In CD testing, there is not a separate variable or measurement called optical amplitude noise, but the equivalent, I11 amplitude and delta is tested, so any variability which would impact BLER is recorded. Variations in I11 amplitude which exceed stage 1 spec are called Drop Outs, and Drop Out Length or DOL is part of the Philips Yellow-Book CD-ROM specification along with I11 amplitude, double-pass birefringence (optical phase modulation), and a metric ****-ton of other parameters. Many a day...hell year of my life went into diagnosing and correcting deviation of these parameters of the now-obsolete media format...
dang! the forum deleted my totally called-for cussing!
Howie
Howard Hoyt
CE - WXYC-FM 89.3
UNC Chapel Hill, NC
www.wxyc.org
1st on the internet
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