Syntrillium Backup Forums :: View topic - How to reduce or eliminate cassette tape warble?

DGalbra862 · Posted - Sun Jun 01, 2003 5:43 pm

Hello and thanks for the help.

How do I reduce or eliminate cassette tape warble?

I'm trying to repair and preserve the audio on some old cassette tapes. (These tapes contain oral family history that I've been asked to preserve on CD.)

Unfortunately, one tape has some warble that I've been unable to eliminate. (I've tried retensioning the tape on multiple machines, playback on 3 different cassette players, and minor head re-adjustments. While these efforts reduced the warble, they did not eliminate it.)

Is there a digital tool that can remove some (or all?) of this cassette tape warble? (I have Cool Edit 2000 with the noise reduction modules.)

Thanks for the help,
DGalbra862

ozpeter · Location: Australia

Do you mean a varying change of speed? I doubt very much whether it would be practical to correct it - you'd have to go through it second by second making individual corrections.

- Ozpeter

zemlin · Location: USA

nope - it ain't gonna happen. Since the pitch of the speech is always changing there is nothing that can be used as a reference to calculate the speed of the tape at any point in time. If the tape had a strong 60 Hz hum or some such "constant" it might be possible through some convoluted means, but not with any normal tools.

OBuckley · Posted - Mon Jun 02, 2003 4:33 am

This does depend on what is causing the warble. Could be speed variations on the original tape (perhaps aka "flutter"), in which case there isn't much you can do about it. On the other hand, I have had a number of effects which could be described as warble which result from non-flat spool winding (re-spool the cassette a couple of times) and more often, differences in tape head alignment between the machine the tape was recorded on and the machine you are playing it back on (or with discrete heads, on the same machine even). As this forum regularly stresses, if you are going to transcribe a tape, optimise the playback head alignment to the tape you are going to transcribe before putting the content anywhere near the digital domain. That may do quite a lot to fix your problem - and even if it doesn't, it will fix a lot of other problems you didn't know you had.

SteveG · Location: United Kingdom

OBuckley is right - there are quite a few things that can affect cassette replay. Spooling the cassettes is always a good move - if they are very sluggish to wind, take them out and bang them flat on a table quite hard - this tends to loosen up the tape pancake a bit. And make sure that the capstan and pinch roller are clean, and in the roller's case, free to move and still fairly flat! And check that there are no other obstructions or obstacles in the cassette path - you'd be amazed at what I've found in the front of cassettes! Sometimes, the felt pads behind the tape get hardened and go 'scritchy', and this can also lead to degraded playing. And if the deck hasn't been switched on for a while, let it run first before transcribing anything from it - the wow and flutter figures tend to improve anyway when the lubrication has warmed up slightly!