CBS LABS Dynamic Presence Equalizer model 450

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CBS LABS Dynamic Presence Equalizer model 450

Post by orgoblo » Wed Feb 21, 2018 6:55 pm

Hi Group-

Can anyone PLEASE refer me to a USERS MANUAL for the model 450?? I can't find one to save my life. On that note: What the heck is this unit good for?? I preseume to 'equalize' the audio in a range of maybe 2-4KHz. And I suspect it was designed to meet these needs for the BC AM back in the 60's?? Also: These are rarely listed...perhaps trashed?? I seem to read in these blogs about 'What did it do? The needle rarely moved. No adjustements! Took it out of service to make for one less 'power waste' in the audio chain'" Not very informative or flattering.

Oh well....its a shame as I'd love to try one in my present CBS Labs TWINS audio chain for my AM station.

Thank you group!!

Dave in Grass Valley, CA

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Dale H. Cook
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Location: Roanoke/Lynchburg, VA

Re: CBS LABS Dynamic Presence Equalizer model 450

Post by Dale H. Cook » Thu Feb 22, 2018 7:29 am

I have never seen a manual for the 450 (original model, 2RUs) or 4500 (later model, 1RU).

The principle use of the Dynamic Presence Equalizer was to improve the sound of the human voice when transmitted over a less-than-optimal path, such as an unequalized phone line with poor high frequency response. Most of the energy of speech is in vowels in the 100-1kHz range, while most of the information is in consonants in the 2-4 kHz range. The 450/4500 automatically detected and compensated for loss in the presence (2-4 kHz) band. It had a detector that could distinguish voice-only programs from music programs, and was automatically disabled during music programs. The reason why your needle hardly moved was probably because you were running music through it, thus disabling it.
Dale H. Cook, Contract Engineer, Roanoke/Lynchburg, VA

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