I accidentally noticed that my DCC 300 is running slow. A 90 minute DCC also lasts 96 minutes, while an ACC heard “by ear” goes a bit slower … now, while a digital recording is practically insensitive to tape speed (right?) analog playback is not. … do you know if you can adjust the running speed of the tape and if this, once adjusted, has an influence on the digital recordings already made?
The service manual tells you how to adjust the speed. Basically you put in an analog reference cassette and adjust it until it runs at the right speed. You would need something that can tell you the frequency of the signal like a frequency meter or an oscilloscope, but if you have good hearing, you may also do it by comparing the tone between the system under test, and another reference system that you know is good. It’s fairly easy to do.
The playback speed of a DCC cassette is based on a crystal, so if the cassette was recorded at a speed that’s actually too slow, the electronics will automatically adjust the playback speed to match the speed of the recording, so it will sound exactly the same.