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 Post subject: Re: Unusual optical soundtrack
PostPosted: Fri May 08, 2015 1:45 pm 
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Ken Layton wrote:
That's a "push-pull" variable density track. The two tracks are 180 degrees out of phase with respect to each other. I have one of those tracks on a 16mm trailer for The Day The Earth Stood Still.

That track on your 16mm print is probably a reduction from a 35mm print. To properly play it back you need a push-pull optical sound head (common with 35mm soundheads) which has a phototube with two pickup elements inside it like a type 920.



What was the purpose of the out of phase tracks, Ken?

Do 16mm projectors exist with such an arrangement?

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 Post subject: Re: Unusual optical soundtrack
PostPosted: Fri May 08, 2015 1:52 pm 
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Push-Pull tracks were intended to be used in a theater sound system which had a push-pull phototube in the soundhead and used an amplifier with a push-pull output stage. This was to give greater sound output with less noise, a primitive noise reduction system so to speak.

If a push pull track was played on a normal sound head, it would have a reduction in volume. This is much like playing a Dolby stereo optical track on a mono soundhead. Yes it plays back, but at lower volume.


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 Post subject: Re: Unusual optical soundtrack
PostPosted: Fri May 08, 2015 2:35 pm 
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Interesting.

How about 16mm projectors with this system? Do they exist?

Well, Robert, there's your answer.
:smile:

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 Post subject: Re: Unusual optical soundtrack
PostPosted: Fri May 08, 2015 5:06 pm 
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I don't know for certain which 16mm machines would have been capable, but it would have definitely been one with a tube amplifier containing a push-pull output stage and a phototube for the optical sound pickup. Probably one that used either an 868 (mono) or 918 (mono) phototube which could be directly interchanged with a type 920 (push-pull or stereo).


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 Post subject: Re: Unusual optical soundtrack
PostPosted: Sat May 09, 2015 7:09 am 
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I received an email from Paul Ivester which had done the rounds with members here. There is a difference in the scan of my soundtrack and the one I received of a push pull soundtrack. On mine both tracks are identical. I am using a Bell & Howell 655 and the film plays normally.
Attachment:
optical.PNG
optical.PNG [ 204.12 KiB | Viewed 1396 times ]


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 Post subject: Re: Unusual optical soundtrack
PostPosted: Sat May 09, 2015 7:28 am 
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I have a quad variable area soundtrack in 16mm, is this unusual?


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 Post subject: Re: Unusual optical soundtrack
PostPosted: Sat May 09, 2015 11:46 am 
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Robert Crewdson wrote:
I have a quad variable area soundtrack in 16mm, is this unusual?


Sounds like you have a "Maurer" track which is actually 6 tracks. It's explained on page 606 of the book I referenced earlier.

Very common track.


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 Post subject: Re: Unusual optical soundtrack
PostPosted: Sat May 09, 2015 12:32 pm 
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Robert:

After examining your variable density track more closely, it's not push-pull. It's a dual variable density I have never seen before. Do the two tracks stay exactly alike throughout the entire print?


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 Post subject: Re: Unusual optical soundtrack
PostPosted: Sat May 09, 2015 2:05 pm 
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Ah, it remains a mystery. This is the first interesting topic I've come across on any of the forums in a while.

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 Post subject: Re: Unusual optical soundtrack
PostPosted: Sun May 10, 2015 11:02 am 
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Here is are 2 images of what I called Quad Variable Area. You can see that it has 4 tracks, not the 6 of the Maurer.
Attachment:
quad.PNG
quad.PNG [ 263.47 KiB | Viewed 1375 times ]


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