Cassette recording timing

When I used the VAAS USB Cassette Capture device and Audacity software to create a aud or mp3 file I would get a file with about 104 minutes from a C90. I was concerned that the files were bigger than they should be. I thought most of my C90s had approximately 94 minutes on them. Even though the files I was getting were about 10% longer than the originals they sounded normal. Then the device stopped working because I dropped it.

The replacement device Super USB Cassette Capture by ezcap seems to have a problem with speed in the other direction.

One tape I have (Grease) shows on the Cassette info side one 32:09 and side two 31:30 for a total of 63:39. Using the first device I got 67:51 and with the second device 59:15. For a C90 that should have about 94 minutes I was getting about 104 minutes with the first device and 88 minutes with the second. The sound seems normal from either device. I am just trying to understand tape speed.

If the time recorded is shortened, the music will be slightly higher pitched, and if lengthened, slightly lower pitched.

You can use Effect > Change Speed to change the length and pitch to what it should be. See the formula to do this here: .


Back in the good old days (1980s) the speed of the capstan in the cassette decks could be highly variable. I had two different Tascam cassette decks and a Tascam 34B open reel deck. The 34B ran accurately to time, every time. The two cassette decks never ran to the same precise time as the 34B. Add to that, if the cassette casing was slightly warped and the tape inside was poorly wound, there could be some friction drag as the tape spools rotated.

I would suggest that, if you are getting +/-10% accuracy on your cassette players, you’re probably getting it as good as it will be.