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Re: [AV Media Matters] Reel players capable of playingat17/8and3 3/4 ips

Another speed correction technique for audio recordings from poorly
regulation portables is the play the originals on an instrumentation
playback deck that has external servo speed control.  You can connect an
audio oscillator of the appropriate servo control frequency, and tweak
exact speed control frequency to improve the voice quality.

Record copies on a high quality speed controlled deck.

On some portables, the speed might be varying enough to require "riding"
speed control via the oscillator on the instrumentation playback deck
the External servo input feature, but on others this might be adequate
slight fixed speed correction.  Those Scientific instrumentation
built to IRIG standards of the aerospace industry required either 100 or
kHz nominal external speed control frequency, or at worst a 400 kHz
frequency, which audio bench oscillators of the Hewlett Packard 2xx
could deliver.  The common function generators might work, but are not
stable as the laboratory grade audio oscillators.  Besides HP, Leader,
and a
number of others, (Philips of Holland) made suitable oscillators.  The
Wavetek XCG series had good oscillators.  (183 XCG model).

This high servo frequency is divided down to get the 1 7/8 IPS accurate
speed control by the instrumentation transport.

Stuart Rohre
Applied Research Labs, UTX

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