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TAPE SPEED DEVIATION
1.
Method involving use of pre-recorded tape.
For measuring the tape speed diviation, play back the
pre-recorded
tape
at
1,000Hz+ 0.1%.
Connect
the
appropriate
output to a frequency counter meter in
order to measure
the tape speed deviation from the
resulting deviation of the measured frequency.
2.
Method involving use of timing tape. (designed for
tape speed measurement)
This method utilizes a timing tape marked at intervals of
7-1/2". The running time of over 60 marked sections of
tape is measured in order to calculate the deviation of
the tape speed. In applying this method, however, it
should be kept in mind that the timing tape stretch or
contract
measurement
enor
is inevitable,
so that it is
necessary to measure
the total length of the tape in
advance.
WOW AND FLUTTER
Playback the 3,000 Hz pre-recorded tape of which the
wow and flutter level is guaranteed to be smaller than
0.07% for measurement by means of a wow meter. It is
also possible for a 3,000 Hz sine wave
to be recorded
and played for measurement
by means
of the wow
meter. In this case, however, the wow meter indicates a
value as much as twicc the value given in the specifi-
cations on the first page.
FRQUENCY RESPONSE
RECORD :
1) Give a sine wave of 1,000 Hz to the Line Input of
the recorder
to be tested through an attenuator
from an audio frequency generator.
2) Set the Record/Playback Knob to "Rec" position
and adjust the line input volume so that the VU
Meter needle indicates "O"' VU.
3)
Set
the Equalizer
Switch
to 7-1/2"
or
3-3/4"
position.
4)
Under
the condition
described in (2), lower the
input level 16 db by means of the attenuator.
5)
Record the spot frequency in the range of 30 Hz to
25,000 Hz from the audio frequency generator.
PLAYBACK :
6)
Set the Record/Playback Knob to "Play" position.
7)
Connect a Vacuum
Tube Volt Meter to the Line
Output Jack. (VTVM with milli volt scale.)
8) Playback the reocrded tape.
9)
Playback the recorded spot frequencies and make a
memo of output level and plot the value on a graph.
Mic. input
Oscillator
Microphone
Line output jack
TOTAL HARMONIC DISTORTION FACTOR
1 KHz
Distortion
meter
Audio
Oscillator
do=d-di_
dz
where,
do = Required
d = Overall distortion factor
di = Noise level
d2 = Distortion factor of the oscillator
(Note : New tape of particularly good quality should be
used for measurement of the distortion factor.)
SIGNAL TO NOISE RATIO
M-10
Set the Equalizer Switch to "7-1/2 ips" position and
playback a tape containing a 25 Hz sine wave recorded
at "O"
VU
level on a standard recorder. Connect
a
V.T.V.M. to the line output jack of the recordir and
measure its output. Then remove the tape and measure
the noise level under the same condition. Convert into
decibels each of the measured values.
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