Radio Road Which tuner to get and getting the most from it. Thank God, for the radio!

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De-emphasis.....

Posted by doodlebug (A) on August 9, 2006 at 15:10:42

In Reply to: Re: European tuner in the US posted by Marantzguy on August 8, 2006 at 16:24:39:

is different on FM broadcasts in Europe vs US. The US system used a 75 micro-second - what you mentioned as time constant - de-emphasis network where Europe used a 25 micro-second time constant.

This de-emphasis arrangement is *roughly* equivelant to the RIAA curves found on LPs. That is, the highs are boosted at broadcast time at the FM station and the low frequencies are reduced. Then the FM tuner reverses the arrangement - de-emphasis! - which then reduces hiss and noise picked up in the reception.

Some older tuners had a switch on the back to change this out - or sometimes found inside. By the 80s, though, these had disappeared due to parts count reductions.

BTW, Dolby tried to get into the FM broadcast noise reduction business and you'll find a number of 70s vintage tuners with the de-emphasis switch on them labeled Dolby something-or-other as a result.

I doubt that you'll hear much difference in today's FM broadcasts with a tuner in either position.

Hope that helps.

Cheers,

David

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