I have quite a few old cassette tapes that I'm transferring to CDs. But some of the tapes are not labeled as to whether they were recorded with Dolby B encoding or not. I know some were and some weren't, I just don't know which is which. I try to detect it by ear (switching the Dolby decoder on & off on the cassette deck where I'm playing the tape), but sometimes it's really hard to be sure, especially with just a short listen. Is there a more objective way to detect quickly whether the tape was recorded with Dolby B? Maybe some sort of spectrum analysis?
Wayne Parham Messages: 18782 Registered: January 2001
Illuminati (33rd Degree)
Dolby B is really just treble pre-emphasis with automatic gain control. I've noticed a lot of store bought tapes from the seventies were so cheap they didn't have much HF extension, so the pre-emphasis was lost. My suggestion is to test them by ear, because even if you know a tape was recorded with Dolby B, if the tape doesn't have much on it above 10kHz, I don't think I'd want the Dolby B decoder to take away what little was left.
I guess you're right, I probably should just judge it by ear.
By the way, these are not commercial cassettes, they're amateur recordings of original music, so the signal was messy & unreliable to begin with. Therefore, as you pointed out, even if I knew how it was recorded I might as well play it back with whatever settings sound best.
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