Why do audio cassettes go odd?

April 22, 2005 5:07 AM

I commute and run to books on tape. Every so often, I will get a spate of too fast, high pitched Alvin Chipmunk playback. Flip the tape to side B at the same point- no problem. Flip it back- Alvin. Change tape player- same thing, so it seems not to be the machines. At worst this can go on for an entire side. A solution would be welcome (slapping tape firmly does not help, nor does rewinding), but mostly I'm wondering, what gives here?
posted by IndigoJones to Technology (10 answers total)

Best solution would to be to make the jump to some type of digital media player and avoid the analog mess. There are so many advantages to using an mp3 player and they can be had for just as much as 6-10 audio tapes. I know this isnt exactly an answer to your question, but just a suggestion. There is tons of content available for download on the net.
posted by askmatrix at 5:27 AM on April 22, 2005

It's probably happening because the capstan and pinch roller aren't grabbing the tape and letting it play too fast, raising the pitch. As for why it happens on one side and not the other, just leave it to dumb luck and alignment of the tape. To try to fix it, clean up the capstan and rough up the rubber surface of the pinch roller a bit so it can grab the tape. If that doesn't work, the spring that holds the pinch roller in tension is probably weak or broken, and you're best off buying a new tape player or an MP3 player like askmatrix suggested.
posted by zsazsa at 6:12 AM on April 22, 2005

i think your tape must be slipping between pinch roller and capstan. see diagram here. the spools are wound at a higher rate than the tape, to keep things tightly wound, and my guess is that this is pulling the pae through too fast.

however, i have no idea why that would happen. you could try cleaning the roller and capstan with alcohol and a q-tip.

maybe the problem is that whatever the clutch mechanism is on the spool drive (since it wants to go round faster than it can there must be something that "slips") is sticking? you could open it up and clean the insides. don't know if it would help.
posted by andrew cooke at 6:12 AM on April 22, 2005

Best answer: If this happens on more than one cassette player, the problem must be the tape. I happen to know how these tapes are reproduced and the fact that this happens from time to time is not surprising at all. The duplication process is very fast -- think rewind speed or faster. Sometimes one small slip in the duplication device can create wierdness like this.

I should mention that this cheap-but-fast duplication works only for speach. Music doesn't copy well this way.
posted by kc0dxh at 8:07 AM on April 22, 2005

Change tape player- same thing, so it seems not to be the machines.

Then it sounds like a screw-up during the recording, to me. (One easy-to-imagine scenario has the story-reader speaking into a battery-powered recorder, with the batteries running down, slowing the motor. Then you play back at normal speed, and Alvin is with us again.) Hope you're renting these tapes, or better yet, checking 'em out of the library.
posted by Rash at 8:32 AM on April 22, 2005

Response by poster: Sounds reasonable. I put too much faith in Quality Control, I expect. Also, I'm just surprised that no one points this out to the library so they can get a replacement.

Of course, I'm surprised at a lot of public indifference to library and other public property.

Many thanks for all responses. I particularly like mechanical diagrams. And I believe I will move to the 21st century soon. Perhaps with the tax refund....
posted by IndigoJones at 9:11 AM on April 22, 2005

another for jumping to digital media - just get one of these bad boys to convert your cassettes to mp3.

Alternatively of course you could just plug a tape deck into your computer, capture and convert, but it's not nearly as cool. Or fun....
posted by forallmankind at 9:55 AM on April 22, 2005

This used to happen to me on my car stereo. The tape deck was only rated for 90 minute tapes. I played a lot of 100 minute tapes on it. Some of them would occassionally go into Chipmunk mode. Flipping the tape and then flipping it back sometimes cured the problem, sometimes not.

I assumed that this was caused by the weight of the tape somehow screwing up the play rate.
posted by alms at 10:14 AM on April 22, 2005

kc0dxh probably has it, but there is one more thing to try, just in case. Put the tape in another player. Fast forward all the way to the end, rewind, FF again, rewind again. This should retension the tape.
posted by bh at 10:56 AM on April 22, 2005

Response by poster: Thank you bh, I'll try that. And I am intrigued, forallmankind, by plusdeck. Interesting little techno niche they've carved for themselves, could answer a few medium range issues....

Again, thanks to all. I always learn something in these fora.
posted by IndigoJones at 6:34 PM on April 22, 2005