[rcag_ils]

Is it the rpm of the motor shaft? The pulley? Lead in/out of the record? Or the belt? Or what? The outer rim of the platter with the dots on a DD turntable? If so, the tracks won't be 33 1/3.

[SET Man]

Hey!

 The record turns 33 1/3 revolutions per minute  The gear, pulley, motor and etc of the tunable all have to spin the record constantly at that speed.

Take care,
Buddy 

[timind]

A quick look at Wikipedia should help.
http://en.wikipedia.org/wiki/Gramophone_record

[rcag_ils]

then ipm are not the same.

[neobop]

33 1/3 is the rotational speed of a long playing record. The platter must rotate at this speed to play it back correctly. If you have a 45 record, the platter must turn at 45 revolutions per minute for correct playback. This would be the rotational speed of the spindle and platter (and record).

If you have a belt drive table the pulley speed will be different. It's the platter/spindle speed we're talking about. If you have a strobe display on the outside of a platter, there is usually one set of marks for 33 1/3 and another set for 45. When speed is correct, the marks will be stationary, when lit, for the respective speed. If the marks look like they're going forward (same direction as rotation), then it's running fast. Conversely, going backwards would be slow. Hope this helps.
neo

[BaMorin]

Is it the rpm of the motor shaft? The pulley? Lead in/out of the record? Or the belt? Or what? The outer rim of the platter with the dots on a DD turntable? If so, the tracks won't be 33 1/3.

The only part of the platter system that won't be going 33.3 rpm is the exact center of the spindle, which would be zero rpm.......but that is at the atomic level. all other parts will be 33.3 rpm. the velocity of the outer parts in relation to the inner parts of course will cover more ground. But any part other than exact center will be 33.3........unless your platters are fluid.  I think you are confusing groove velocity for rpm.
The platter should pass a given point 100 times per minute

[Johnny2Bad]

Is it the rpm of the motor shaft? The pulley? Lead in/out of the record? Or the belt? Or what? The outer rim of the platter with the dots on a DD turntable? If so, the tracks won't be 33 1/3.

All but the belt, actually (assuming we accept the possibility of direct drive). The belt isn't making a circle and connects two rotating assemblies that normally are differing diameters (and thus different RPMs), so RPM isn't really an appropriate reference for the belt itself.
More specifically, it's the RPM the record itself should spin to maintain correct pitch of music and voice. Although we usually take this to mean the platter travels at that same RPM, a careful turntable designer would not assume the record cannot slip on the platter.

then ipm are not the same.

Far from it. The record or platter rim could travel at inches per minute, inches per second, all the way to beyond the sound barrier (where shock waves may cause it to deteriorate or even break up), depending on the diameter of the platter or album, while still maintaining 33 1/3 rpm.
Also, when playing a conventional LP record, the velocity of the stylus through the groove varies; faster at the outer grooves than inner. This is a direct result of RPM being constant.

[rcag_ils]

Then the inch/sec should be longer in the first track and shorter in the last track, making first track sound better than last track.

[Wayner]

It is at the mercy of the RPM of "the small wheel", or the drive pulley (and there is a hitch).

Circumference is the messenger here, as it's appropriate length (in circular terms) and the belts length driven by the drive pulley (and its RPM) is what produces platter RPM. It is a by-product of drive RPM, drive pulley diameter, and "large wheel" diameter (where belt meets platter).

Let's say our platter is 11.50" in diameter and the belt drives on this surface. If we take Pi X diameter we get 36.128 inches.n That is the length of belt travel required to make the platter go around one time.

Now, the diastance of motor drive pulley from platter must be considered as that is also an element to determine belt length. Let's say that number is 8".

As some of you with some math/geometry skills are starting to figure out, the drive pulley diameter and the RPM of the motor are going to have a major influence on the platter speed. The distance between the drive pulley and the platter plus contact area of platter and drive pulley, will determine belt length.

Since the motors are a fixed RPM and is not a variable, that truly leaves the drive pulley and belt length as the only 2 numbers that can be fooled with unless we change the platter diameter, or create a sub-platter (like a REGA or Empire).

When the design is all done, it will be about a big wheel, a little wheel, a belt and the total contact area that will determine the drive pulley's diameter.

This is also why trying to fit another manufacturer's motor and pulley onto your turntable probably won't work. There are just too many parts to the equation.

Wayner

[rcag_ils]

My point is the first track has to sound better then the last since it has more inches of information at the same speed as the last.

[Elizabeth]

33 and a third is 100 every three minutes.
1,000 every thirty,
And 2,000 rev an hour. exciting what math can do for you...
48,000 a day
17,520,000 a year.. (standard year, not true Solar year...sigh...)Solar year is closer to: 17,531640 rev per year...

[Wayner]

My point is the first track has to sound better then the last since it has more inches of information at the same speed as the last.

Correct you are sir! It's called data compression as the tonearm sweeps in towards the label. Same information, less space to put it in.

Wayner

[SET Man]

My point is the first track has to sound better then the last since it has more inches of information at the same speed as the last.

Hey!

     I think I've read it somewhere before that you loose high frequency as you get near the center of the record. I don't notice much of the different, but that must be because even at near the center the respond is still beyond my hearing anyway.

     Strangely enough I do noticed this effect with my 109 years old acoustical gramophone playing early 78s disc. The high seem a bit less near the end of the disc... don't know maybe it was something else in play.

     Anyway, it amazing that all of this needle dragging along the groove work at all right? 

Take care,
Buddy

[rcag_ils]

Strangely enough I do noticed this effect with my 109 years old acoustical gramophone playing early 78s disc. The high seem a bit less near the end of the disc... don't know maybe it was something else in play.

I thought the bass needs more "length", and the length gets shorter towards the center. Is it why the record company always pur their "#1 hit" on track 1, 2, or 3. I know there are exceptions, but usually the good songs are being put on the #2 track.

[Wayner]

Spot number 2 on a side is a golden spot. The first song is always subject to needle drop damage, and soon becomes noisy in the first few seconds. it is also usually a high mechanical distortion area because it's outside of the first null point. Song number 2 usually is at the first null point (considering the usual 3.5-4.0 minute songs).

So, not only do we have to consider that the music is becoming compressed, it's also dancing around the 2 null points. Exactly between the 2 null points, the distortion curve also goes up and then starts to go to near zero when it reaches the last null point (if that is in the record groove area).

Yeah, it's a wonder it all works at all.

Wayner 

[marknoir]

Is it the rpm of the motor shaft? The pulley? Lead in/out of the record? Or the belt? Or what? The outer rim of the platter with the dots on a DD turntable? If so, the tracks won't be 33 1/3.

R u guys for real????