CD stoplight - some analysis

Excellent post lawrie, we will of coarse have a very steep mountain to climb to meet your 'personal approval', however I'm quietly confidant, that we may be able to raise the odd eyebrow in the medicore sea of 'sameness', and thanks again lawrie for your unerring surport, it's sends waves of upbeatiness rippling through the corridors of O/A, to which there is no price that can be put on that. cheers Wm & the O/A team

 

Seems a somewhat strange approach to system building if you ask me, but then you wouldn't

Just think, if you found say the Trivista with HokeyPokey Cable to sound better than an 861 at half the price, but bought the 861 because you didn't explore the possibilities. IMO, all good dealers do this, and have a good idea of what works with what. they can even demonstrate this blind

Still. What you don't know won't harm you Lawrie

 

Ah well, a potentially interesting thread bites the dust.

-- Ian

 

What a great word.

 

I quite agree Ian. Meaningless measurements taken with scant regard for random errors, with the likelihood of definitive answers for pussies within the next two years.

What a shame we couldn't keep that one going

 

There's nothing "meaningless" about attempting to measure whether a tweak has any effect on the output of a CD. It's a member of the category of things that can be filed under Useful Information. In this event, the test is compromised, but it's beyond me that some people seem to be so pained by the very idea of measuring something.

Measurements have an important place in hi-fi (there wouldn't be any manufacturer quality control without them, for a start). Subjectivists just make themselves look daft when they fail to understand this elementary point.

We now return to our normal programming ("I use my ears!", "It's all about the music!", "Nordost Valdoonican is the best!", "I never ever fool myself").

-- Ian

 

Merlin,

Strange approach it is but it works for me. Changing your kit every month works for you but then as as someone with a box fetish and very little interest in music, that's understandable. Anyway, as long as you are happy with constantly shifting boxes, then that's what counts. Sometimes reading your posts about your box swaps reminds me of a dog chasing it's tail. Ever seen one do that? It leads to nowhere.


Ah, WM!

Flattery will get you everywhere. Anyway, I did notice some fighting talk in between the lines which appears to to me that you are laying down the gauntlet for the other cable merchants or audio companies out there? Am I getting warm or or am I getting warm? Well good luck with that WM and I look forward to reading some magazine reports on the myth busting products that you will be unleashing on the unsuspecting public.

Btw, whatever happened to those digital boards that you once predicted by PM to me (around 18 months ago) that when inserted into CDPs, they would make TTs obsolete due to their sonic qualities being more analog than even TTs? The reason ask is that since that comment, there has been an explosion in new TTs and accessories hitting the market and I was just wondering whether those digital boards did indeed make it into the market place or whether you miscalculated the effect or impact of the digital boards on CD replay. Any comments? or should I wait for Bristol?




Enjoy the music,

Lawrie.

 

Firstly, it's not me having it both ways (I said many pages ago I can't hear any difference using the Stoplight pen, although I won't discount out of hand that others can). Secondly, I've only come across the Stoplight pen recently, but I have never seen any claims of it reducing bit errors, only jitter. I'm not sure any of the older links that have popped up in this thread have actually explicitly claimed the stray light causes bit errors either. I don't think my point is irrelevant though, since it does seem at least reasonable to debate what the manufacturer claims the mode of operation to be.

Anyway, would I be correct in assuming you'd say that the green pen tactic would make bugger all difference to jitter? Go on, humour me with an explanation.

Martin

 

Accepted, and in that case it's even more hypocritical to have railed so unconstructively against the attempts to elicidate "Useful Information".

I hope this thread doesn't die before such an elucidation - but if it does then I can only assume pointless sniping from the likes of Merlin and Lawrie, abetted by WM and others, (none of whom have contributed anything useful to this discussion) have killed it off. This attitude is certainly making me question the value of remaining on this forum.

 

Graham, it was just such experimentation that led me to accept that there could be audible differences without variations showing up in the frequency response plot. So personally I would not suggest it is hypocritical, although the sniping that comes from the likes of Lawrie and the Pussies really does require a response. The trouble is Graham, if I tell people that alterations to transient behavior of frequencies above 30khz can clearly affect the perceived authenticity of a cymbol, everyone blats out the usual school book crap and quote various accepted (if ancient) theories.

So I cannot be bothered to argue the point. If that's unacceptable to you I'm sorry. But don't stop posting Graham, the likelihood is that troublemakers like Me and WM will soon clear off anyway, as this place just ain't the same anymore with all these physicists poisoning the minds of the free.

Ah typical Lawrie FWIW, I've had my speakers two years, and have only had one amplification change during that period. So I'd say it's pretty stable mate, unlike you.

If you refuse to allow someone free reign to demonstrate the differences amongst products that you poo-poo in a blind test, purely because you have either a sad predjustice or a fear of knowledge, then I truly feel sorry for you.

But never mind, you can always swap another box, as you seem to spend your whole life doing judging from the epic descriptions of your rivetting testing procedures that appear like a pox across the internet

But before posting here, or anywhere else for that matter, it really would be great if you could check your facts and stop yourself from becoming the subject of numerous private jokes

 

Oh come off it. This is absurd.

And I do think the battle between you and Lawrie is getting quite tiresome, can't it be carried out by email instead?

-- Ian

 

Sorry Martin I do understand you arent wanting it both ways. This is the first time I have heard of the jitter thing related to the green pen. It is has always been relating to stray light. That is how the joke started. It does appear that a manufacturer is trying to wriggle a bit, as the original use has been totally debunked by designers of Laser Pickup systems for cd/dvd hardware.

I am having a problem in working out anyway what so ever, how some green ink on a CD will have an effect on anything, other than making a mess on your fingers.

 

Merlin,

That is one of the most hilarious comments that I've read from you for a while. You really are a bad judge of character aren't you? Do you really think that I give a **** what you and your buddies discuss about me in private? In fact, I'm chuffed that you could go to the trouble to even discuss me in private when I don't even consider or think about you beyond my keyboard. Really chuffed, dude! I really am!

So you've had your speakers for two years? Congrats and enjoy swapping your boxes or should that be ...............



Enjoy the music,

Lawrie.

 

Glad to see you're thick skinned Lawrie rather than just thick

Must come in handy with your diplomacy

With that , I respectfully withdraw........

 

It is still of course a stray light issue, but the claim is that this causes jitter. To quote the link I put up a little while back:

Having enough stray light bouncing around a CD to causes complete misreads always struck me as unlikely, but that a small amount could add background light noise, changing slightly the optical signal to the pickup doesn't seem impossible. There is also it would seem a chance that the green ink round the edge might reduce this. When I asked a few pages back about how if at all such a change in the light signal might affect the electrical digital signal, notaclue gave a link from someone saying it would make no difference. Do you think there is any way an increase in optical noise could affect the jitter of the electrical digital signal? This to my mind is the critical question.

Martin

 

Martin
Page 8 of this thread third post from the bottom. Read that again.
That is how the laser pickup system works. Stray light is not an issue.

When we were working on an IBM DVD technology a few years ago, which is now in production machines worldwide. We tried firing all sorts of lasers at the pickup system.
No problems occured.

The only problem that I have encountered was when we subjected the product to earthquake type conditions. But then you would expect that wouldnt you.

 

Right, I've read that a few times and I still don't quite see how it answers my question I'm afraid. If there is background light bouncing around the CD at random, surely some small amount reaching the detector will be sufficiently coherent with the 'true' signal to potentially have an effect, however small?

 

This bit Martin

In order for edge reflections to have ANY effect, the total round-trip distance traveled between the current pit being read and the edge MUST be an exact integral multiple of the wavelength, AND the returning spurious reflection MUST be significantly brighter than the direct beam illumination AND has to have been created in the first place. That means that the angle of incidence has to have been sufficiently shallow (not 90 degrees, like the entire system is configured, but more like 20 degrees!) to begin with to cause enough energy to find its way to the edge

Because it is configured at 90 degrees no light can bounce around and accidently go into the detector. Because the only way it could hit the bottom of the pit is if it came from the laser in the first place. If it hits the side of the pit it would bounce away harmlessly. Have you ever seen a CD player with glass or perspex lid?.
If this really was a problem, they just wouldnt work at all. I think 47 labs do a CD player where the disc sits on a spindle on top of the player. Loads of cash too. It works fine.

Green light has a wavelength of 514 nm and the laser diodes used in cd players emit at 790 nm. I would be very interested to hear a theory on how exactly a layer of green ink which is definitely NOT optically flat can reflect or absorb anything.

 

Depending what happens after the light signal is received this may all be totally irrelevant, and/or the effects I'm talking about may be infinitesimal due to the tightness of the coherence requirement, but...

OK, I'm probably being dumb, but can you explain to me where on earth that 20 degree requirement comes from?

Why necessarily harmlessly?

Well, if there were scattered light around, only a very small amount would reach the detector within whatever coherence window is set... Plus it would be much lower level than the true signal...

Rough surfaces are perfectly capable of absorbing light. It's the absorption characteristics of the ink that matter, not the colour light it reflects that matters too. An appropriate ink would in general be totally be capable of absorbing the 780-790nm CD laser light.

 

The laser pickup system is at 90 degrees to the bottom of the pit.
If it was at 20 degrees (which is just an example) then it might be effected by reflected light, but it isnt.

If the reflected light that it bouncing around like a young lad on a space hopper! doesnt hit the bottom of the pit then it is not read so it is harmless. That is what I meant.

My last paragraph on re-reading it was poorly written. Of course a non optically flat surface can absorb things. That is what you get for typing too fast.

It may well be possible to get an ink that would absorb the infra red light, but these products are not sold as having special ink. It is the green colour that is "special"