Speed of groove.

Interesting question. Since the variation of tangential velocity that occurs across the record is presumably the same when the record is played back as when it is cut, and since one period of a given signal frequency will extend over a physically longer distance if it is located towards the outer edge of the record than if it is located towards the inner edge, I believe that it all cancels out. Signal frequency will be reproduced identically at the two locations, because the time required to traverse the distance corresponding to one period will be the same in the two cases. Signal amplitude at any instant of time, which is proportional to groove velocity at that instant, will also be maintained for the two locations, because as tangential velocity decreases towards the inner part of the record, a given groove excursion will occur over a correspondingly shorter distance, and therefore in the same amount of time, and therefore with the same velocity.

Regards,
-- Al

I think what you are saying is the velocity decreases as the stylus moves towards the inner groves of the record. If I'm not mistaken, output is specified by cartridge builder at a specific velocity; however, I don't know where that location may be on a 33-1/3 RPM LP record.

At some point of time on this post I saw response from Al (Almarg) but it dissapeared.
???

The linear velocity of the groove at the stylus starts out at about 20.1 inches/second and finishes at about 8.7 inches/second. That is based upon the following: 33.3 rpm, outer groove 5.75" from center and inner groove 2.5" from center. It is a simple formula: V=2Pi*r*33.3333/60 (rev/sec) r is in inches so you get inches/second. Cartridges have a rated output voltage at a given lateral velocity. That is defining the amplitude of the stylus motion. The output isn't really affected by groove speed, but by the amplitude and velocity of the stylus motion. The stylus is coupled to a tiny generator and the voltage output is an AC signal that varies in frequency and amplitude based on the stylus motion which is driven by the record grooves. So a 1 kHz waveform, for example, (the squiggles in the vinyl) at the outer groove of the record will be longer than a 1kHz waveform at the inner groove. The musical information is essentially packed tighter at the inner grooves of the record because the linear velocity is lower. 2.3 times tighter to be exact.

12-29-11: Marakanetz
At some point of time on this post I saw response from Al (Almarg) but it dissapeared.
???

I deleted it, and posted the revised version you can see above. My first submittal wasn't quite right :-)

Regards,
-- Al