Painting the edge of a CD green

[ginetto61]

... The ADC was a Tascam UH-7000 modified to use an external power supply.

 

Hi and sorry if i jump in with a OT question.

I have read about issues with the original power supply.

As i should receive soon this Tascam i would be extremely interested in getting some more info about your mod.

Have you written something somewhere ?

Of course please free to contact me privately.

Thank you very much indeed.

Kind regards, gino

[mansr]

Hi and sorry if i jump in with a OT question.

I have read about issues with the original power supply.

As i should receive soon this Tascam i would be extremely interested in getting some more info about your mod.

Have you written something somewhere ?

Of course please free to contact me privately.

Thank you very much indeed.

Kind regards, gino

I haven't written anything, but maybe I should. I'll start a thread for that when/if I do.

[ginetto61]

I haven't written anything, but maybe I should.

I'll start a thread for that when/if I do.

 

Hi and thanks for the reply and yes please.

I have received the units just now. I placed the order before reading about the noise issues.

If there is a cure i would be very interested to know it.

Thanks and regards, gino

[gmgraves]

A couple words about this "tweak", it came out in the days when CD players used IR lasers, there are almost none of those left today, most people are either using a DVD drive which uses a red laser or BluRay which of course uses a blue laser. The color of the beam is important since the explanation was having to do with the absorption of the beam by the green ink. The correct ink was also important since it was about the IR properties not the visible properties.

 

That's a good point. Yes, supposedly, the theory behind the green pen, was that the shade of green used was the complementary color to infrared and therefore it would absorb any reflections scattered within the polycarbonate and eliminate spurious reflections back into the photocell, thus reducing jitter and lowering the error rate. If one is using a drive employing a red laser, (DVD) or a blue laser (Blu-Ray), by definition, the green color of the ink would have little or no effect as there is little to no spectral relationship between the green and the laser color. Good thinking!

 

So using generic marker ink would not necessarily work the same, and using a modern player would almost certainly not behave the same as a CD player from the day.

 

So doing a test using generic ink with a modern player has very little to do with whether it WOULD have worked with the correct ink and old style CD player.

 

Of course it is a perfectly viable test of whether generic ink works with a modern player.

 

Note I am not saying it DID work back then, just that generic ink with modern player is not an appropriate test of whether it did.

 

John S.

 

Exactly. My conclusion was that it did NOT work, even back in the day, but it most assuredly won't work with today's players as even multi-laser players would not be using infrared to read even red-book CDs.

[gmgraves]

I used a CD player from 1982. Is that old enough? Also, even modern players have to use an IR laser for CDs since otherwise the reflections wouldn't cancel properly.

 

I suspect that modern multi-format players use a red laser to read red-book CDs. I don't know about modern CD-only players (does anyone still buy those?). There would be no reason to stick with infrared, Red lasers have a smaller "footprint" and therefore I suspect would be less susceptible to tracking errors than an infrared laser.

[mansr]

That's a good point. Yes, supposedly, the theory behind the green pen, was that the shade of green used was the complementary color to infrared

 

That's nonsense. Complementary colours exist only as an artefact of the human visual system. Since infrared is invisible to humans, it doesn't have a complementary colour.

 

and therefore it would absorb any reflections scattered within the polycarbonate and eliminate spurious reflections back into the photocell, thus reducing jitter and lowering the error rate.

 

Any colour (as perceived by humans) of pigment would do provided it absorbed the relevant wavelength of light. Still doesn't actually work though.

 

If one is using a drive employing a red laser, (DVD) or a blue laser (Blu-Ray), by definition, the green color of the ink would have little or no effect as there is little to no spectral relationship between the green and the laser color. Good thinking!

 

Exactly. My conclusion was that it did NOT work, even back in the day, but it most assuredly won't work with today's players as even multi-laser players would not be using infrared to read even red-book CDs.

 

A pressed CD can only be read with a laser of the proper wavelength. Every drive capable of reading CDs has an infrared laser. That's why combo-drives need multiple lasers. Moreover, green pigment is quite likely to absorb red light. It wouldn't be green if it didn't.

[gmgraves]

That's nonsense. Complementary colours exist only as an artefact of the human visual system. Since infrared is invisible to humans, it doesn't have a complementary colour.

 

Picky, picky, picky! Perhaps I should have said "complementary wavelength".

 

Any colour (as perceived by humans) of pigment would do provided it absorbed the relevant wavelength of light. Still doesn't actually work though.

 

Like I said....

 

A pressed CD can only be read with a laser of the proper wavelength. Every drive capable of reading CDs has an infrared laser. That's why combo-drives need multiple lasers. Moreover, green pigment is quite likely to absorb red light. It wouldn't be green if it didn't.

 

1) Can you show me some documentation that says that a red book CD can only be read by an infrared laser? I'm certainly no optical engineer, but I see no reason why a red laser wouldn't work at least as well. I had a laserdisc player once that would also play CDs. It had one laser and that laser was red (I know because I cannibalized it for the laser diode when the player died).

 

2) Wouldn't the efficacy of the green pigment wrt red vs infrared depend on the exact shade of green?

 

Thanks in advance for the information.

[mansr]

Picky, picky, picky! Perhaps I should have said "complementary wavelength".

 

There is no such thing. The complementary colour notion comes from the human visual system having three kinds of receptors sensitive to red, green and blue light. An arbitrary material can absorb any combination of wavelengths, so no such concepts exists in a broader sense.

 

1) Can you show me some documentation that says that a red book CD can only be read by an infrared laser? I'm certainly no optical engineer, but I see no reason why a red laser wouldn't work at least as well. I had a laserdisc player once that would also play CDs. It had one laser and that laser was red (I know because I cannibalized it for the laser diode when the player died).

 

The pits in a CD surface are one quarter wavelength deep, so light reflected from the pit is half a wavelength out of phase with light reflected from the surrounding area. When the laser illuminates a spot covering both the pit and some area on the sides, the out-of-phase light cancels out, thus modulating the intensity of the total reflection. Light of a different wavelength would see a different phase shift and thus a lesser degree of cancellation.

 

A CD laser has a wavelength of 780 nm, so a 650 nm DVD laser would be phase-shifted by 0.6 wavelengths or 216 degrees. This might be close enough for the detector to still register the difference. However, a 405 nm Bluray laser would be shifted by almost a full wavelength or 338 degrees, which is probably below the detection threshold. Laserdisc uses the same 780 nm wavelength as CD.

 

2) Wouldn't the efficacy of the green pigment wrt red vs infrared depend on the exact shade of green?

 

The IR characteristics of something we perceive as green could be anything. Even two pigments appearing as the exact same shade of green could have radically different absorption of infrared light.

 

Assuming for sake of argument that absorbing scattered light at the CD edge is beneficial, there is no reason the material used for this would need to be green as seen by humans. As long as it has the right characteristics at the wavelength of the laser, it could be green, blue, black, or any other colour, even white.

[Jud]

Pardon my skepticism, but if you and Keith Johnson get different results, my initial thought is not that he's suddenly become sloppy and prone to mistakes.

[mansr]

Pardon my skepticism, but if you and Keith Johnson get different results, my initial thought is not that he's suddenly become sloppy and prone to mistakes.

 

If I knew Keith Johnson's test setup, I could attempt to replicate it. Unfortunately, details about his experiment are sketchy to say the least.

[Jud]

If I knew Keith Johnson's test setup, I could attempt to replicate it. Unfortunately, details about his experiment are sketchy to say the least.

 

Yes, I wish there were more detail as well. (But then I'm always curious to know more, as are most of us.)

[mansr]

Hi and sorry if i jump in with a OT question.

I have read about issues with the original power supply.

As i should receive soon this Tascam i would be extremely interested in getting some more info about your mod.

Have you written something somewhere?

 

Some notes and graphs here: http://www.computeraudiophile.com/f6-dac-digital-analog-conversion/tascam-uh-7000-power-supply-noise-28570/

[esldude]

Pardon my skepticism, but if you and Keith Johnson get different results, my initial thought is not that he's suddenly become sloppy and prone to mistakes.

My second thought is he might give a sloppy presentation intentionally leaving out details keeping in mind his vested interest in doing so.

[sandyk]

My second thought is he might give a sloppy presentation intentionally leaving out details keeping in mind his vested interest in doing so.

 

Next you will be claiming that there was no moon landing, and it was all filmed in Area 51 ?

[sdolezalek]

In a different context, I might refer to this thread, wgscott's: http://www.computeraudiophile.com/f8-general-forum/maybe-spending-stupid-amounts-money-power-cords-isnt-entirely-harmless-28452/, and the ballooning of meaningless polls as a slow news night, but it seems like Computer Audiophile is having a slow news month.

 

Have we finally reached that asymptote where the latest and greatest just isn't that much better than what we already have, where all the big debates have either been resolved or given up as unresolvable...

 

Maybe someone should start an "is audio boring?" poll.

[Jud]

My second thought is he might give a sloppy presentation intentionally leaving out details keeping in mind his vested interest in doing so.

 

Vested interest?

[Allan F]

Next you will be claiming that there was no moon landing, and it was all filmed in Area 51 ?

Or that Elvis is dead.

[esldude]

Vested interest?

Commercial interest would be more correct.

[audiventory]

Some say painting the edge of a CD green makes a difference to the playback, specifically that it affects the jitter. I decided to test this myself. To this end, I burned a J-test track to a CD-R and recorded the playback. Then I painted the edge green and recorded it again. Below is the spectrum of this:

 

[ATTACH=CONFIG]25980[/ATTACH]

 

The blue trace is before painting the edge, the green one after (obviously). While there is clearly some jitter present here, there is no change whatsoever to be seen. There are some very minor variations in the four small peaks not part of the jitter pattern. However, these vary slightly from run to run regardless, so the changes cannot be attributed to the green edge.

 

I can't say I'm surprised.

 

Hi Mansr,

 

For pure experiment need 1000 CD x 100 pens

 

If talk seriously, looks like difference of the graphs in range of measurement / recording / playback errors.

 

Do you know original binary context?

 

Do you checked binary content both recording cases?

 

First need fully describe experiment methodics, scheme and what tools used there. And big numbers of tests.

 

Only all these things in complex allow avoid esotheric resume.

 

Also measurement tools should be certified and specially checked for trust to results.

[mansr]

Hi Mansr,

 

For pure experiment need 1000 CD x 100 pens

 

If talk seriously, looks like difference of the graphs in range of measurement / recording / playback errors.

 

Do you know original binary context?

 

Do you checked binary content both recording cases?

 

First need fully describe experiment methodics, scheme and what tools used there. And big numbers of tests.

 

Only all these things in complex allow avoid esotheric resume.

 

Also measurement tools should be certified and specially checked for trust to results.

 

You're quite right. That's how a proper scientific test would be done. However, I mainly did this to see what kind of reaction I'd get here. As such, much less rigour is needed.

[Jud]

You're quite right. That's how a proper scientific test would be done. However, I mainly did this to see what kind of reaction I'd get here. As such, much less rigour is needed.

 

So it's more of a social experiment.

[Jud]

Commercial interest would be more correct.

 

? Still not connecting the dots (pits? bits?) between possibly causing slightly fewer sales of CD Stop Light among the few people who were aware of his talk and ...Keith Johnson profits!

[alfe]

Hi,

I'm not supposed to participate to this forum anymore

 

Numerical aperture is a very important concept for the design of PUH

If you consider that CD gathers light up to 26,7°, DVD 36,9°, BR 58,2°

Knowing that n=refractive index is 1,55 for polycarbonate and the numerical aperture is NAo = no sinθo

NA= 0,45 for CD, 0,60 for DVD and 0,85 for BR.

If you understand a minimum of optics design you will find out that the green pen is just an other BS concept in the audiophile world.

 

Mansr, You are right even if you can use the same OEIC for CD and DVD you still need two wavelength laser diode.

George before starting arguing, I have a PHD in optoelectronic

 

 

 

[Jud]

Hi,

I'm not supposed to participate to this forum anymore

 

 

...which makes your infrequent appearances all the more welcome.

[ginetto61]

Some notes and graphs here: http://www.computeraudiophile.com/f6-dac-digital-analog-conversion/tascam-uh-7000-power-supply-noise-28570/

 

Hi ! thank you very much indeed for the very kind and valuable reply !

yesterday the beast is arrived ... and it works !

I left it on for about 6-7 hours and no perceptible noise ad the end of the listening session.

I wonder if i have to update the firmware ? i have just loaded the win 7 drivers last version from the Tascam site.

Any advice would be welcome and appreciated.

Thanks sincerely again.

Kind regards, gino