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 Post subject: Dolby FM compensator
PostPosted: Mar Sat 25, 2017 3:19 pm 
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Joined: Jan Mon 24, 2011 7:21 am
Posts: 364
Location: saint clair shores, michigan
Picked this up for 3 bucks on the hunch it was worth it. Who can tell me what I bought?


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 Post subject: Re: Dolby FM compensator
PostPosted: Mar Sat 25, 2017 5:14 pm 
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Joined: Nov Fri 06, 2009 1:04 am
Posts: 2358
Location: Rochester, NY 14425
75us, 25us de-emphasis? 75us for general USA broadcasts and 25us for Dolby I think.


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 Post subject: Re: Dolby FM compensator
PostPosted: Mar Sat 25, 2017 6:43 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3867
Location: Boston, MA USA
Sometime in the late 1970s radio stations were allowed to use 25 uS pre-emphasis instead of the standard 75. Many stations were anxious to do this because they could get higher perceived loudness when playing rock music which has a lot of high frequency content. But to use 25 uS they were mandated to also use Dolby encoding. This would provide"kinda-sorta" equalization for existing receivers with 75 uS de-emphasis. It really sounded dismal and I think has now gone away.

-David


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