[QuadList] New Octaplex recorder design

[Don Norwood]

Phillip.......my replies are inserted below......

----- Original Message ----- 
From: "Phillip G. Shaw"
>
> The "Modern" time date is of interest because the track format clearly 
> shows that the Normal Broadcast 70 mil mono track is split into two 32-mil 
> tracks, labeled Aux 1 and Aux 2.
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Let me clarify....the pic of the "modern" RCA head was just for comparison 
to the older "sandwich" style head.  The format shown on the track 
specification page is specifically for the older Ampex , NOT the newer 
designs as typified by that RCA headwheel.
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>
> The Camden Plant produced all head assemblies for the RCA divisions and I 
> have the proto-type split track audio head created in 1985 for NBC-NYC 
> TCR100's. It's always possible that the GOV version was not available to 
> Broadcast, or the cost from MI stock was prohibitive.
>
> The other curiosity is the location of the "Monitor" record head preceding 
> the rotary heads. This suggests a Pilot tone-synchronizing signal used 
> with the rotary Timing Pulses.
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No, it wasn't a pilot tone, but a clever (if crude) form of confidence 
indication for the record system.  The monitor track was recorded by a head 
driven with DC so that it saturated the tape.  Then, during recording, the 
rotary heads erased the portion of the track that they passed over, leaving 
a track of pulses on the tape.  These were read by the reproduce monitor 
head and used to drive a lamp circuit which illuminated if there were 
pulses, indicating that recording was taking place.
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>
> The system, IMO, is a 2-channel wide band data recorder with additional 2 
> channels of low band Control data on the Aux tracks. Speculation only!
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The two Aux channels were simply 300-15kHz tracks that could be used for 
anything.  I believe I mentioned that an auxiliary multiplexer was available 
to put three voice channels on one of the tracks.  They were not used for 
control track which was a dedicated track as in standard quad.
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>
> The track format suggest that the heads 1 (1-4) are mounted 45 deg from 
> heads 2 (1-4).. Is that true?
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No.  The heads are mounted precisely side by side.  When you look at the 
format specs, you have to assume the tape to be in motion.  The horizontal 
displacement between the two drums is such that the second head enters the 
tape when the first head is 50% across the tape, just the same as occurs in 
the later versions with all 8 heads on a single drum.
----- 
>
> Phillip G. Shaw
>