ELI5: A vinyl record spins at a constant pace, but since it’s circular, the needle is moving across more material at the start of the album. Does this mean they are recorded at different pitches throughout the album to compensate?

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Everyone is right here. But to answer the question more in depth… A master vinyl is etched using a much heavier etching head that has a tracking system to GO INWARDS at a constant rate. This is reflected In how the vinyl is played back except your needle follows the grooves and so is controlled by the grooves. The speed, 45 or 33 rpm, remains constant during master etching and final playback. Though technically you can (and do) master at lower speeds to improve quality. So yes the outer tracks move faster and therefore have higher “bandwidth” or fidelity (even though these are different terms, they both apply)

justapersonortwo

The outer bands have more bandwidth, but the recording device uses the same RPM notion as the player. Neither use the “inches of groove past the needle” measure.

WRSaunders

The recording is done at the same speed as the playback so it sounds just fine, but as you get closer to the centre of the record, there’s not as much vinyl track per second of music, so the fidelity does drop. That’s why on a lot of records that have been mastered with some thought, the tracks with a brighter sound (more high frequency content) tend to be closer to the outer edge of the record, because it’s the high frequencies that become less possible to reproduce as the “inches of track per second of audio” value drops, as it’s naturally going to as you get further towards the middle of the record.

shokalion

It is always recorded spinning at the same constant speed, the same as it is played back, so it never changes. But of course the further in it gets, the faster it gets to the center, but everything is at the same rate. Think of it like writing spiralled around a disk, except the words do not get stretched or compressed. Otherwise this would make it more complicated to record and playback which is unnecessary, because it would mean you would of course need the needle to change size and motor to slow increasingly as it moves further in, which of course not possible to do with the needle being a static unchanging object.

mrbeardo4200

Related fact: video discs coped with this by having two modes: constant angular velocity and constant linear velocity. A CAV disc recorded one frame of video per rotation, regardless of where on the disc it was. This meant that you could skip from frame to frame just by moving over one track. This was great for special effects like freeze-frame, slow motion and also for random access, in video games and image archives. But it wasn’t an efficient use of space: only 30 minute per side could be held. For movies, CLV was used where the data was packed as tightly as possible, and the number of frames per rotation was about 3 at the outer edge and 1 at the inner edge. More could be stored, but “trick play” was limited to chunky jumps and jittery freezes.

moon_monkey