NAB, IEC, CCIR curves for tape emphasis and flux curves

Discussion in 'Audio Hardware' started by vbsh, Apr 28, 2015.

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  1. vbsh

    vbsh New Member Thread Starter

    Hi all,

    My english is not perfect, so I will try to put it as simple as possible.

    I was reading an article about reel to reel tape recording and there's one thing that really confuses me. It mentions that the NAB and the CCIR curves are decreasing the high frequencies at pre-emphasis stage,
    but at the post-emphasis or de-emphasis stage (if I'm correctly using these terms as synonyms), there are complementary curves that boost the high frequencies, so that in the end we'll get a flat frequency range. So far I get this. However, in the other chapters, it mentions that the high frequencies should be boosted at recording. But wait a minute, they just said that the NAB and CCIR curves are meant to roll off high frequencies. Isn't this contradictional or I'm not understanding it right?

    Source: http://www9.dw-world.de/rtc/infotheque/magn_recording/magrec_06.html

    Also, many online articles and online books define emphasis as (I'm paraphrasing): "Boosting the high frequencies at recording and lowering them back at playback", but in the case of NAB or CCIR there's no boosting, but attenuating of those frequencies at the recording stage. Maybe they meant RIAA or maybe something about telecommunications?

    Then, in the following article, we can see tests of various tape recorders' frequency responses, all of them NAB calibrated, and none of them is flat, of course. Then whats the point of all this de-emphasis thing if it doesnt give flat response in the end? Please check the pics there.

    Source: http://www.endino.com/graphs/

    Thank you very much.
     
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