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In Reply to: RE: Pop quiz: Why do CDs play from the inside out? (nt) posted by geoffkait on June 02, 2023 at 04:18:45
It is related to your OP. As we have discussed on other forums, the CD laser tracking system does a great job of tracking the disc - if it lost track, as you suggest, there would be no music and, for me, that is a very rare occurrence and only with badly scratched discs. There is a significant amount of run-out with a spinning CD due to all the reasons you mentioned plus the mechanics are low cost and the tracking system is designed to compensate for all of those and keep the laser following the spiral. The tracking range of the system is larger than the acquisition range so it acquires at the inside where there is less run out and is then able to track the increasing run-out as it moves to the outside edge.
Follow Ups:
I've already pointed out the tracking system doesn't work 100%. Yes, I know it was designed to avoid the problems of vibration and flutter. If it did this tweak wouldn't work. The Reed Solomon codes don't work 100% either. Those "scientists and engineers" did the best they could at the time. If you could hear what I've heard with my ears.
" Those "scientists and engineers" did the best they could at the time"
And that "time" spans 40 years! You don't think they learned anything new? Still no commercial adoption of these so called fixes.
No, I don't. There are a number of things they never learned, most prominently,How to deal with external vibration.
How to deal with internal vibration.
How to deal with fluttering of the CD.
How to deal with scattered laser light.That's giving them the benefit of the doubt. That's assuming they were ever aware of those problems, which they probably weren't.
Edits: 06/02/23
Worked a bit on this back in the 90s and came up with some tweaks.
- Removed the magnet-clamp, running a diy sorbothane mat on top of the cd`s
- Using antistatic fluid on the sorbothane-mat
- The most audible tweak is to copy cd`s to hd and burn out copys. The copys are 100% centered and has no pvc protection layer covering the data. Makes them a lot easier to read, more air & cleaner sound.
Done a lot of tweaks to the cd-player, like upgrading digital clock, upgrading trafos++ and bypassed(!) the analog filter (multibit)
My favs, in no particular order are Intelligent Chip, crystals on top of CD palyer, vibration isolation, stabilizing disc with black 3M electrical tape, determine absolute level of disc while sling, absorb scattered laser light inside transport.
You think the consumer electronics industry as a whole never considered the any of the issues I noted?
You are the only person on Earth that has?
Ridiclous!
As I've already stated either they didn't know about the problems, which they probably didn't, or they didn't know how to fix the problems. Kind of like you, now that I think about it. No offense.
Edits: 06/05/23
Ok so let's review this again I stated the following design engineering issues above:
How to deal with external vibration.
How to deal with internal vibration.
How to deal with fluttering of the CD.
How to deal with scattered laser light.
You still claim the community of consumer electronics engineers world wide did not know about and take these issues into account in the design of CD players?
Ridiculous!
Stop putting words in my mouth. What I actually said was the designers/ manufacturers were probably unaware of these issues AND - even if they were - they chose to ignore them OR were unable to figure out solutions.To make the situation more complex than it already is, there are differences in performance among the various types of electrical tape, 3M Super 88 outperforms 3M Super 33, for example. Does that surprise you? I mention this not so much for your sake but for anyone who might actually be interested in trying this tweak.
Edits: 06/06/23 06/06/23 06/06/23
I contend that all these issues were accounted for in original system design. There are billions of CDs in use but only one Geoff - who you gonna believe?Actually, I keep an open mind with tweaks but I really think someone has to show a real problem to justify the tweaking rather than audiophiles tinkering with things for the sake of it and then claiming an improvement.
If we're going to go down the Roy Batty 'you won't believe the things I've heard' route we'll need a calibrated Geoff by submitting him to controlled listening tests.Regarding vibration I post the this link to Jurgen Reiss of MBL again (CD transport discussion starts at 3:40). As he is trying to sell very expensive equipment he takes the Fear-Uncertainty-Doubt approach to say how sensitive the CD transport is to external vibration. But, what he is actually saying is the CD pick-up mechanism works so well keeping the laser on track that you can use it as a vibration measurement system. As long as you keep any servo current modulation out of the audio path you are golden.
Edits: 06/02/23
If you look hard enough you can always find someone who believes CDs are the greatest thing since Skippy peanut butter. What else is new? I had the displeasure to hear the bug MBL system at Vegas twenty years ago, remarkably bad sounding. Thump, thump, thump. What else couid he say, oh, my company's electronics won't sound very good unless you do a lot of tweaks. It's German engineering. Lol
Edits: 06/02/23 06/02/23 06/02/23
Fixes would need to be backwards compatible.
Reengineering the system and changing too much would be a non-starter, even if certain benefits could be demonstrated.
Too much is never enough
Some fixes do not (rpt not) have to be backwardly compatible. Some examples:
1. The super transparent clear layer used in SHM-CDs from Japan.
2. Audiophile fuses
3. Some method of absorbing CD laser scattered light.
4. Dampening of CD tray, CD transport
5. Seismic isolation system
6. Absorb internally generated RFI.
7. Cryogenics
First they would have to be aware of the problem. Which they probably aren't. Then they have to figure out how to do it, which they may or may not be able to do.
But none of these tweaks require modification of the format. After all they can be done at the kitchen table with materials obtained at any office supply store.
Again, where is the commercial adoption?
Commercially tweaks like this aren't on the agenda manufacturers. You're confusing manufacturers with audiophiles. SHM-CD in Japan uses a non polycarbonate clear layer with higher transparency, so at least someone is interested in performance. Polycarbonate is only about 91% transparent to the CD laser. Does that surprise you?List of audiophile tweaks that are commercially non-starters:
1. Audiophile fuses
2. CD liquid enhancers
3. CD stabilizers
4. Seismic vibration isolators
5. Scattered CD laser light absorbers
6. Method of eliminating RFI
7. Control of all wiring directionality
8. Dampen vibration of transport mechanism/CD tray
9. Cryogenic applications
Edits: 06/03/23 06/03/23 06/03/23
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