PBS Idiots

Thank you for so quickly demonstrating that you have absolutely nothing intelligent to contribute to this thread.

Rest snipped, presuming it's based on equal ignorance of the laws of physics.

Phil

--
I tried the Vista speech recognition by running the tutorial. I was 
amazed, it was awesome, recognised every word I said. Then I said the 
wrong word ... and it typed the right one. It was actually just 
detecting a sound and printing the expected word! -- pbhj on /.

Good point. And space-time is warped by the sun. And we're not in a vacuum so there's air resistance changing the motion. And the record's not likely to be completely flat. And... However, no number of 10^-big influences that you can list will ever add up to changing the predicted outcome. Assuming the owner of the record deck has a frisky cat, however, could change the outcome.

Phil

--
I tried the Vista speech recognition by running the tutorial. I was 
amazed, it was awesome, recognised every word I said. Then I said the 
wrong word ... and it typed the right one. It was actually just 
detecting a sound and printing the expected word! -- pbhj on /.

Fuck you, you retarded f*****ad.

I got more on the ball than a retarded, pissy little bitch like you does.

Ahh... so his whimsy is OK, but I am to be ignored? OK, Phil. You just made the grade of "dumbfuck of the year".

What is between your ears is obviously in a vacuum.

I remember these records when I was a kid that the teacher had at school. They had like 4 or 5 concentric grooves per side. They were kid stories about farm animals and the like. They were arranged so the story would go along and it would end on one record with something like "and Billy looked down and saw a..." When you played the next record it'd tell you what he saw. Only each time you played the records, because of the concentric grooves, the story they told would be different! It was clever!

On Nov 29, 2:21 pm, Archimedes' Lever wrote:

You guys are homing in on it but you need an old-timer to set you straight. To solve the problem of "skating" and the "anti-skating" device, you have to understand one missing fact. That fact is that the phonograph cartridge is mounted at angle to the line going back to the arm pivot. This is called an "offset arm". Therefore the force of the friction of the needle in the groove acts on a line that is at an angle to the line from the arm pivot. I know you guys studied statics but are trying hard to forget it all, but if you resolve the force vectors of the friction against the force provided by the arm pivot you find that because of the offset a radial force is present. The anti-skate device provided a radial force to more or less compensate (the friction forces are sort of variable) for the radial skating forces. In a straight arm the friction forces tend to act directly back upon the pivot and don't create the skating. There reason for offset arms is that they produce less "tracking error". That is since all records are cut with a linear translation of the cutting head a perfect playback would require a cartridge aligned tangent to the grooves at all points on the spiral. While linear playback mechanisms DO exist, most phonographs used the offset arm which produced much less tracking error from the outside to the inside of the recording for an arm of a given length. That is why except for every early (1930s) transcription players offset arms were always used. OK?

The idea of the eccentric end grooves for 78s was that record changer mechanisms were designed with this sort of ratchet affair on the arm. When the arm moved inward toward the center of the recording the ratchet simply slid over the teeth on a lever arm. But when the arm moved in an outward fashion, it tripped the lever which cycled the record changer. The idea was so records of different diameters and different amount of playing times would all cycle the mechanism.

Early LPs sort of followed the same standard.

But the 45 was supposed to be a complete redesign of record "technology" to make it "up to date". These changes involved a re- thinking of records designed for single songs. The 45 rpm speed made them much smaller and lighter than 78s. The higher speed then 33 was used because of a tendency of 33 LPs to loose high frequencies at small diameters. Also the modulation was much higher than LPs for improved signal to noise (and cheaper player electronics). The large center hole and the fact that label part of the center of the record was thicker than the plastic right at the hole allowed a new changer to be designed where the stack of records were dropped onto the turntable with just a center post mechanism with blades that came out between records to hold them and drop them. [78 changers had edge mechanisms to drop records and often chewed the tiny center holes.]

Finally the icing on the cake was a new standard that determined the diameter of the final lead-out cut. This meant that the changer could be activated (as all later were) by position of the arm near the center of the recording rather than with the ratchet gizmo. And it was soon obvious that this was a better way for LPs as well. Especially since the finer grooves of the slower records meant that it would be hard on the cartridge and difficult get enough force to use the eccentric trip mechanism.

Hey! I just checked wikipedia and they don't seem to have anything on

45 rpm records! They need an article like this.

neat, if you only had to play one side of each it'd work great on an "auto-stacker"!

Except they weren't concentric, the were interlaced normal records have each song recorded concentricly. concentric means the items are differentiated by their radius.

pretty much everone else in this thread has been abusing the term concentric too.

It is NOT concentric if the groove spirals inward.

A hard drive has concentric tracks, even though they are not "visible".

An album is a spiral or "worm" style.

They are not "grooves"... It is a SINGLE groove.

The folks talking about extra tracks refer to "multiple tracks". It is similar to screw terminology. It is like a "double thread" screw.

Nonsense. A helix has a 'centre'. Two interlaced helices can have a common centre. In this case they are concentric.

Yes concentric circles are differentiated by their radii, no that is not what concentric means.

--
Patrick Hamlyn   posting from Perth, Western Australia
Windsurfing capital of the Southern Hemisphere
Moderator: polyforms group (polyforms-subscribe@egroups.com)

It's concentric to the centre of rotation of the record. As is the spiral groove.

A spiral groove which is stamped slightly offset results in a record which speeds up and slows down every two seconds or so. It *really* needs to be concentric to the centre of rotation.

I had a record which was stamped like this, but you can (relatively) easily observe the effect if you shift the centre hole of a record.

--
Patrick Hamlyn   posting from Perth, Western Australia
Windsurfing capital of the Southern Hemisphere
Moderator: polyforms group (polyforms-subscribe@egroups.com)

No it doesn't. Squares don't have radii, but can still be concentric. All that is required is that the objects under discussion have a sensible concept of a centre. Which includes spirals too.

Well, I can see one who is.

Phil

--
I tried the Vista speech recognition by running the tutorial. I was 
amazed, it was awesome, recognised every word I said. Then I said the 
wrong word ... and it typed the right one. It was actually just 
detecting a sound and printing the expected word! -- pbhj on /.

Jasen Betts wrote: ) concentric means the items are differentiated by their radius.

Nope. That's, at best, what it implies. And not even always.

) pretty much everone else in this thread has been abusing the term ) concentric too.

'concentric' means 'having the same center'. This should be immediately obvious by looking at the word itself.

Compare 'eccentric' (from ex-centric) which means 'not having the same center'.

Also compare 'concurrent', which means 'happening at the same time'.

SaSW, Willem

--
Disclaimer: I am in no way responsible for any of the statements
            made in the above text. For all I know I might be
            drugged or something..
            No I\'m not paranoid. You all think I\'m paranoid, don\'t you !
#EOT

Not true. A concentric ring to a central point is a cylindrical shape. A spiral toward such a central point is NOT a concentric path. One

*could* argue that it is "very nearly concentric", just as I can argue that it is technically not concentric.

Any given arc segment of a spiral comes very close to being a concentric segment around a central point, but still fails.

That is why the terms "eccentric" and "out of round" exist. Since the spiral is not truly round, it is not correct to refer to it as a concentric ring.

The only thing on a record album that is concentric to the center hole is the outer edge(though not always), and the gaps between each track, though their lead in and lead out even negates that claim.

It would "speed up and slow down" with EACH rotation of the disc.

And NO, it does NOT change the "needle through the track speed" AT ALL.

What changes is the track speed at which the needle is tracking the recorded signal with respect to the speed at which the needle was tracking when the record was mastered. It varies as the needle tracks from the outer edge to the innermost groove lead out. There would have to be quite a large eccentricity between the hole punch and the groove placement for this to even be detectable.

It can be observed by placing a 45 on a 33 spindle, and offsetting it. There is not, however, enough of an offset in an album hole-to-groove to be detectable, even in the worst cases.

Said the overtly, perversely eccentric retard.

Time is what keeps everything from happening all at once.

h

ly

But I'm not disputing any of that. The original discussion was about how a tonearm can move from one groove to another when the grooves consist of concentric circles.

All I've said is that an "end groove", which would be a seperate groove in that context, doesn't exist. The issue of whether the spiral ends in a circle, is eccentric or concentric, is irrelevant since it is connected to the spiral.

Unless you have a record with 750 concentric circles as tracks, all your points are meaningless.

In precisely which of these messages, this being your references header, is that the topic under discussion:

?

Phil

--
I tried the Vista speech recognition by running the tutorial. I was 
amazed, it was awesome, recognised every word I said. Then I said the 
wrong word ... and it typed the right one. It was actually just 
detecting a sound and printing the expected word! -- pbhj on /.