Dolby A

Dolby A is a four channel sound format – left, center, right and surround. It was in use from approximately 1975 to 1986, when it was largely replaced by Dolby SR.

Dolby A vs. Dolby SR

Dolby A is difficult to distinguish from Dolby SR by sight. Here are some tips on telling them apart:

• Many studio films made between 1975 and 1985 will have Dolby A tracks.
• Some (but not all) films with Dolby A tracks will display the word "Dolby" - or "Dolby Stereo" rather than "Dolby SR" - with the Dolby logo in the end credits. But be careful, just because you see one of these in the credits of the film does not guarantee that it is A Type or SR. Some films were released as both mono and stereo prints, or a film may have been re-mastered and released as SR but was originally mono. Seeing the logo in the credits is just another clue to be used with alongside other sources of information.
• Some (but not all) films with Dolby A tracks will display the words "Stereo" on the edges of the film leader.
• A Dolby A track played in Dolby SR will usually sound harsh or blown out

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  Dolby Stereo logo.

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  Dolby Spectral Recording logo (SR)