Tape Recorder Trouble
Have you ever had a tape recorder and wondered, why it doesn't increase the speed and pitch of the sound while playing. if you are thinking because it's speed is constant, think again, while playing, one wheel becomes bigger and the other one smaller. Is it constant ?
Labels: thinktank
posted by ToM at
8:32 AM
9 Comments:
Actually, there's what I call a "pinch" wheel. This is usually a small rubber roller that presses against a smaller steel peg. The tape runs between the peg and the rubber wheel and it controls the tape so that it moves at a consistant speed over the magnetic reader.
That was too difficult ;)
ragnot's right. The tape moves across the head at a constant speed, driving by his "pinch" wheel. The reals just provide tension in opposite directions to keep the tape from unwinding. The rpms of the reals change based on the diameter of the tape around each wheel.
if the reals controlled the speed, then the RPM of the reals would be constant regardless of the diameter and the taps speed at the head would change.
Both reels can't have the same speed, except when they are equally full.
The reels do have different speeds.
Depending on the MODE, Play or Rewind, one reel pulls the other... in the rewind mode the pincher stops pinching.
LOL
Even though the wheels will have different velocity ratios depending on how far through the tape you are, the average size of the two wheels is always the same, so the speed is constant.
essayist
Even if the tape didn't move at a constant speed, it is likely that the tape would have been recorded under the same conditions that it would be played in, in order to compensate.
As I understand it, you record to a tape, and then must rewind and watch it with the tape running the same direction.
(ignoring this pinch wheel, as i do not know all about tapes) surely it would work without the playback being sped up anyway, because,
as you record the tape is speeding up. therefore, as playback is at the same point in the tape, and it goes the same direction, playback will always be the same speed as the original was recorded at.
however, i cannot say for sure :P
Although last Anonymous's point is valid, the wow and flutter would be diabolical.
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