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Old 23rd January 2013, 10:23 PM   #31
popilin is offline popilin  Argentina
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Quote:
Originally Posted by SY View Post
Would you base a calculation of the information contained in a digital file on the covalent radius of a silicon atom?
Of course not !, soon I will do the calculations for the estimate, once I had on hand, but now can not find it.
Is that German Mr. Alz-someone...
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Old 24th January 2013, 02:46 AM   #32
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Although PVC is a polymer chain and can become very large, for simplicity we assume that the molecules are spheres of about 1 nm in diameter.
Record grooves can be cut to a maximum modulation of 0.1 mm.
This gives us about 10^5 molecules, so system resolution is one part in 10^5, or about 16.6 bits.

Assume now, for simplicity, that the stylus touches the groove on a single molecule.
Average groove speed is 2.5 cm/s, so the number of molecules passing the stylus is about 25x10^6/s.

Then, a vinyl record can be thought as a sampling system with a rate of 25x10^6 samples per second and a resolution of 16.6 bits.

Of course, due to mechanical limitations of the system, this number should be substantially reduced.

For a CD, 44.1 KHz * 16 bit = 705600 bit/s
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Old 24th January 2013, 03:58 AM   #33
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Originally Posted by Don Hills View Post
As other have pointed out, you are basing your assertions on an incomplete understanding of the physics.
That's true, I'm just a TV repairman.

If I had a complete understanding of the physics, I would have won the Nobel Prize, would be rich and famous, and I would not be here wasting my time in answering to you.

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First, the radius of a stylus tip in contact with the groove spans many molecules, providing an averaging effect. You can't get "1 molecule width" resolution. Second, it is difficult and expensive to record frequencies higher than about 20 KHz, and almost all cartridges simply won't reproduce them with any accuracy anyway.

Expanding on the second point, at the cutting stage the lathe simply runs out of headroom as the frequency rises. The signal being fed to the cutting amplifiers and head is heavily boosted by the "reverse RIAA" equalisation curve. Also, the head requires more and more drive to obtain a given cutting velocity as the frequency rises. You can't keep boosting the power because the head will burn out. CD4 (quad) records, with frequencies up to 45 KHz, were cut at half speed. Standard stereo discs can also be cut at half speed, but this brings a new set of problems at the low frequency end.
Trying to record frequencies above about 20 KHz is mostly a waste of time, anyway. At the reproduction end, the stylus cantilever / suspension of most cartridges resonates somewhere between 19 KHz and 23 KHz. Output drops off rapidly above this point. This is a deliberate design choice, the increased output around resonance compensates for other losses that are becoming significant at these frequencies.
No need try too hard to find Phono Cartridges that pass 50 KHz.

These do not resonate somewhere between 19 KHz and 23 KHz. AFAIK.

Denon Phono Cartridge Home Page

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Originally Posted by Don Hills View Post
For further reading, I suggest this page:
Digital Vinyl ? !
If elementary kinematics, is your idea of a complete understanding of physics.
BTW. Someone should explain to the author that the stylus has two degrees of freedom.
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Old 24th January 2013, 05:24 AM   #34
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Originally Posted by popilin View Post
...
No need try too hard to find Phono Cartridges that pass 50 KHz.

These do not resonate somewhere between 19 KHz and 23 KHz. AFAIK.

Denon Phono Cartridge Home Page
Note the complete lack of frequency response charts or specification of the amplitude variation within the claimed bandwidth. +/- 3 dB? 10 dB? 20 dB? Also do the math, as on the web page I referred you to, and realise that there is no stylus profile in existence that will allow tracking a 70 KHz signal. Even if the rest of the cartridge is up to it, the stylus won't fit in the grooves. Maybe if the disc is cut at 78 RPM... I stand by my statement, having likely seen more frequency response graphs of cartridges tracking test records than you've had hot dinners.

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If elementary kinematics, is your idea of a complete understanding of physics.
BTW. Someone should explain to the author that the stylus has two degrees of freedom.
You appeared to be lacking even that understanding, so I figured a simplified explanation was in order. By the same reasoning, only one degree of freedom is relevant the lesson he was imparting. If I have underestimated your understanding of the physics involved, then I sincerely apologise. All I had to go on was the level of knowledge you had just demonstrated.
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Old 24th January 2013, 09:30 AM   #35
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Quote:
Originally Posted by popilin View Post
Although PVC is a polymer chain and can become very large, for simplicity we assume that the molecules are spheres of about 1 nm in diameter.
That's not how polymers work and that's not how plastic compounds work. If you start with a bad assumption, you'll end up with a nonsense result.

PVC looks like a pile of tangles of spaghetti (the aspect ratio of the molecules is strand-like and they form groups looking like domains) interspersed with jagged boulders of varying sizes and irregular lumps of clay. Now this is just the medium- if you add in what happens when the grooves are cut, the metallization of the master, and the molding process, then understand that you're not using an AFM to trace the contours, the poor information density that one actually sees becomes clearer.
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Old 24th January 2013, 12:48 PM   #36
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Quote:
Originally Posted by Don Hills View Post
You appeared to be lacking even that understanding, so I figured a simplified explanation was in order. By the same reasoning, only one degree of freedom is relevant the lesson he was imparting.
The author's reasoning is more cheating than mine, not only ignores the two degrees of freedom, the equations are also misspelled, makes a mixture of coordinate systems.
When you make a formal mathematical presentation, the first thing to say is what coordinate system using, is the stage where the action takes.

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If I have underestimated your understanding of the physics involved, then I sincerely apologise. All I had to go on was the level of knowledge you had just demonstrated.
Please, my friend, no need to apologize.

As for my level of knowledge, just let me do some contribution from time to time.
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Old 24th January 2013, 01:03 PM   #37
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That's not how polymers work and that's not how plastic compounds work. If you start with a bad assumption, you'll end up with a nonsense result.

PVC looks like a pile of tangles of spaghetti (the aspect ratio of the molecules is strand-like and they form groups looking like domains) interspersed with jagged boulders of varying sizes and irregular lumps of clay. ...
Dude, if you are going to theorize on molecules (or make-up chemistry) be aware that Sy is a specialist!
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Old 24th January 2013, 01:51 PM   #38
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That's not how polymers work and that's not how plastic compounds work. If you start with a bad assumption, you'll end up with a nonsense result.
True, but I have a good alibi.
I misplaced the original article and the assumption was crucial to obtain a resolution comparable with the other support.
Let us agree that the resolution is not very far from reality, something between 14-bit analog FM broadcast, and 16-bit CD.

Quote:
Originally Posted by SY View Post
PVC looks like a pile of tangles of spaghetti (the aspect ratio of the molecules is strand-like and they form groups looking like domains) interspersed with jagged boulders of varying sizes and irregular lumps of clay. Now this is just the medium- if you add in what happens when the grooves are cut, the metallization of the master, and the molding process, then understand that you're not using an AFM to trace the contours, the poor information density that one actually sees becomes clearer.
This is very enlightening, but I must confess that the theory of condensed matter is not my favorite.

BTW. Hope you do not offend what I said about your soldering iron.
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Old 24th January 2013, 01:56 PM   #39
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I wasn't offended because I didn't understand what you were talking about.
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Old 24th January 2013, 02:05 PM   #40
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I wasn't offended because I didn't understand what you were talking about.
I referred to the resolution of the photos.
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