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

[rohre@ARLUT.UTEXAS.EDU]

Another speed correction technique for audio recordings from poorly
speed
regulation portables is the play the originals on an instrumentation
type
playback deck that has external servo speed control.  You can connect an
audio oscillator of the appropriate servo control frequency, and tweak
the
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"
the
speed control via the oscillator on the instrumentation playback deck
via
the External servo input feature, but on others this might be adequate
for
slight fixed speed correction.  Those Scientific instrumentation
machines
built to IRIG standards of the aerospace industry required either 100 or
200
kHz nominal external speed control frequency, or at worst a 400 kHz
frequency, which audio bench oscillators of the Hewlett Packard 2xx
series
could deliver.  The common function generators might work, but are not
as
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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