Date:         Sun, 28 Sep 2008 11:48:56 -0700
Reply-To:     Association for Recorded Sound Discussion List
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Sender:       Association for Recorded Sound Discussion List
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From:         Jack Honeycutt <[log in to unmask]>
Subject:      motion picture amps (optical sound)
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Folks....

Hello.  I am new here. My name is jack.  I am interested in optical 
sound.  Optical sound as it was used in motion picture sound tracks 
from the 1920s until maybe the 1970s.  Most of my background is in 
Auricon branded variable area and variable density optical 
sound.  But currently I am working on the first 16mm sound-on-film 
camera that was released to the general public back in 1934.  It is 
called a RCA PR-25.  This camera was unique in several ways, but one 
was its approach to optical sound.  It could do it in two ways.  One 
way was what RCA called "Newsreel Sound" and the second was what RCA 
called "Studio Sound".  In Studio sound mode it used a different 
galvo (galvanometer), an outboard amplifier, battery pack and 
microphone.  While many after market amplifiers were made to support 
this and other sound-on-film cameras, the stock RCA amplifier was 
called a PA-94. And the stock magnetic microphone was a RCA PB-111.

I have enough data on the galvo to adapt a Auricon VD amplifier to 
drive the studio galvo.  And I can probably find a microphone that 
would work.  But the studio galvo will be impossible to find.

It is a long shot, but I thought I would toss this out in case we 
have any motion picture sound folks here.  I am looking for a 
schematic of the RCA PA-94 amp.  I am also looking for the amp, 
galvo, microphone, cables etc..  If anyone knows where I might find 
this hardware, please let me know.

I have extensive Auricon documentation. Both original Auricon 
literature and modern data sheets on Auricon vacuum tube amplifier 
repair.  I have moved a great deal of it to the web as high quality 
pdf files and I give it away free.  If you are interested in optical 
sound as it relates to 1920s- 1960s movie cameras, you are welcome to 
join the Auricon Optical Sound users group.  While it is called 
"Auricon Optical Sound, we work on all aspects of early optical sound 
- 16mm as well as 35mm from all vendors.  Here is the web site:

http://movies.groups.yahoo.com/group/Auricon_Sound/

Not trying to give a plug here (this is a very small niche area, we 
are not looking to expand our base of users unless you are 
interested) - but a offer of free documentation to researchers and 
hobbies who need it.  We ask for no money and the user group sells 
nothing. But if the stuff we give away free ends up on ebay for 
someone's profit, we might get cranky.

Any tips on what I am looking for would be appreciated.

Thanks in advance.

jack