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Single Ended Triodes (SETs), the ultimate tube lovers dream.

a bit more on motion picture sound

gilmorneau, hi. Compensation (tone) networks were used in RCA theater amplifiers not just WECO. These are found in the voltage amplifier section. My understanding is these were simply ways to taylor playback for houses (theaters) where clarity of the optical soundtrack (or sound-on-disc Vitaphone playback) needed boost or cut. Instructions are given in the operating manuals of RCA theater playback systems so at installation tweaks could be made one way or the other as needed. Let us not forget that theater sound made its debut with the Vitaphone Corporation system using aparatus with turntables in synch with projectors - WECO apparatus all the way. Sam Warner (Warner Brothers) was instrumental in getting a relationship established with WECO that almost became a monopoly for motion picture sound. Sadly Sam died before seeing the full flower of this technology. Also, needless to say, Warners did not achieve a monopoly. RCA became an eager WECO competitor once sound on film was perfected. Early playback probably did not exceed 5K Hz. By 1939 the upper limit was 10K Hz although RCA amplifiers were capable of much higher. Bandwidth limits mainly reflect optical soundtrack limitations. By the late 30's the RCA variable area optical tracks were easily superior to the WECO variable density. The primary objective when setting up a playback system was intelligibility of spoken word hence the slang term 'talkies'. It was RCA that coined the term 'High Fidelity' and should be given credit for it even at this late date. RCA had to invent ways to equal or better what WECO was doing because they certainly didn't want to use WECO patents and have to pay royalities. There was also the RCA-Victor (Victor Talking Machine Co, Camden NJ) sound system for motion pictures which used exposed & processed film (all black) and a needle stylus to literally cut the sound track on the film emulsion. Advantage? Instant playback. Disadvantage? Noise and bandwidth limitations. Hal Roach Studios used this RCA-Victor system. Roach released through MGM so it was common to see both Western Electric and RCA-Victor simultaneously in the credits. Fascinating subject this. Anyway, a little more info.


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