Not sure whether I should post it here or in the general electronics, but it is related to audio equipment!
As you know, signals on audio tapes will print through to adjacent layers if the tape is left wound up for a long period of time. In the past I have had the misfortune of leaving a tape near a weak magnet, and hearing print-through and partial erasure on just the part of the reel that was exposed to the magnet. I have therefore experimented using an old tape with recordings I don't care about.
My first experiment was to recreate the print-through effect I heard on the tape that was accidentally damaged. After recording some speech, I rewound the tape and put a weak magnet up to the edge of the cassette for a couple of seconds. Upon playback, I heard the print-through effect just like on the accidental one - mystery solved.
Where it gets more interesting is when I put the magnet on top of the tape reel and moved it in a circular motion 5 times. This time, upon playback, I got a very noticeable pre-echo AND a post-echo of the speech throughout the recording!
Later on I took a neodymium magnet out of an old hard disk and rubbed that on the outside of the cassette shell, left to right and up to down several times. Upon playing the tape, the recording was gone - but the tape wasn't silent. Instead there was a rhythmic ‘thump' noise. I can't explain why this would happen, can you?
As you know, signals on audio tapes will print through to adjacent layers if the tape is left wound up for a long period of time. In the past I have had the misfortune of leaving a tape near a weak magnet, and hearing print-through and partial erasure on just the part of the reel that was exposed to the magnet. I have therefore experimented using an old tape with recordings I don't care about.
My first experiment was to recreate the print-through effect I heard on the tape that was accidentally damaged. After recording some speech, I rewound the tape and put a weak magnet up to the edge of the cassette for a couple of seconds. Upon playback, I heard the print-through effect just like on the accidental one - mystery solved.
Where it gets more interesting is when I put the magnet on top of the tape reel and moved it in a circular motion 5 times. This time, upon playback, I got a very noticeable pre-echo AND a post-echo of the speech throughout the recording!
Later on I took a neodymium magnet out of an old hard disk and rubbed that on the outside of the cassette shell, left to right and up to down several times. Upon playing the tape, the recording was gone - but the tape wasn't silent. Instead there was a rhythmic ‘thump' noise. I can't explain why this would happen, can you?
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