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- §, TOTAL HARMONIC DISTORTION
GX-225D
Line
input
—Line
output
Audio
Frequency
Oscillator
Distortion
Meter
Fig. 5
Connect the measuring instruments as shown in Fig. 5
and record a 1,000 Hz sine wave signal at "0" VU.
Playback the resultant signal and measure the overall
distortion factor. Measure the noise level of the tape
recorder without the tape. Connect the audio fre-
quency oscillator directly to the distortion meter for
measurement of the distortion factor of the oscil-
lator. The required distortion factor can be obtained
from the results of the above measurement by the
following formula:
do =d—di
—d2
where,
do = Required distortion factor
d = Overall distortion factor
di = Noise level
d2 = Distortion factor of the oscillator
NOTE: When measuring the distortion factor, new
' tape should be used.
6. CROSS TALK
|
(Cross talk between the channels}
(TAPE)
REV
oy Se ees
GS TAPE DIRECTION
Fig. 6
As shown in Fig. 6, first record a 1,000 Hz sine wave
signal on Track No. 3 at +3 VU level. Next, record
under a non-input condition. Then, playback the tape
on Tracks No. 3 and 4 (reversed condition of tape)
through the B.P.F, (band pass filter sensitivity ...
1:1) and obtain a ratio. between the two from the
following formula:
,
Eo
E2—-E1
where,
C = Desired cross talk ratio (dB)
Bo = 1,000 Hz signal output level
[i
' Be = 1,000 Hz cross talk level
Ei =Non-input signal recorded level Bax
'C = 20 log
(dB)
7. ERASE RATIO
As
shown
in Fig.4, connect
a High Sensitivity
V.T.V.M. to the Line ouput. Playback a virgin tape
and take a V.T.V.M. reading of the output level.
Next, record a 1,000 Hz sine wave signal at +3 VU,
'then playback
this recorded
signal and
take
a
V.T.V.M., reading of the output level. Next, using this
pre-recorded tape, record under a non-input condi-
tion and take a reading of the noise level output of
the erased signal and obtain a ratio between the two
from the following formula:
Eo
Er = 20 log
(dB)
E2-E1
where,
Er = Desired erase ratio (dB)
Eo = 1,000 Hz signal output level
Ez = Non-input signal recorded level
Ex = Virgin tape noise output level
8. POWER OUTPUT (GX-221 only)
High
Sensitivity
output
V.T.VM.
Fig. 8
As shown in Fig. 7, connect an 89 dummy load
resistor
to the speaker
output
and connect this
terminal to a High Sensitivity V.T.V.M. Playback a
250Hz
"0" VU pre-recorded test tape and take a
V.T.V.M. reading of the output level. The resultant
output can be obtained from the above measurement
by using the following formula:
al -2
P= Ww)
where,
P = Desired power output (watts)
E = Measured voltage (R.M.S.)
R= 8&Q
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