Akai GXC-750

5. TOTAL HARMONIC DISTORTION
FACTOR
Audio
Frequency joutput
Oscillator emer Yo
Line
input) GXC-75D
Distortion
Meter
Fig. 6
Connect the measuring instruments as shown in
Fig. 6 and record a 1,000 Hz sine wave signal at
OVU. Playback the resultant signal and measure the
overall distortion factor.
NOTE: 1) At this time distortion of Audio Frequ-
ency Oscillator must be sufficiently small.
2) When measuring the distortion factor,
new tape should be used.
. CROSS TALK (Cross talk between the tracks)
(TAPE)
0)
FWD.
TAPE DIRECTION ==> oF
©
® REV.
—% <@me TAPE DIRECTION
6
Fig. 7
As shown in Fig. 7, first record a 1,000 Hz sine
wave signal on track No. 3 at +3VU level. Next,
record under a non-input condition. Then playback
the tape on track No. 3 and I’ (reversed condition of
tape) through the B.P.F. (1,000 Hz Band Pass Filter,
sensitivity 1,000 Hz, ratio 1:1) and obtain the ratio
from the following formula.
= Eo
C= 20 log g—°E (AB)
where,
C = Desired cross talk ratio (dB)
Eo= 1,000 Hz signal output level (V) [i
E,= 1,000 Hz cross talk level (V)
E,= Non-input cross talk level (V)
7. ERASE RATIO
Line
Audio Frequency |Output Input
Oscillator
|
GXC-75D
Line
Output
Input
High Sensitivity
V.T.V.M.
Fig. 8
As shown in Fig. 8, connect a High Sensitivity
V.T.V.M. to the Line Output. 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 +3VU,
then playback this recorded signal and take a
V.T.V.M. reading of the output level. Next, using
this pre-recorded tape, reocrd under a non-input
condition 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 E, -£, (dB)
where,
Er = Desired erase ratio (dB)
Ey = 1,000 Hz signal output level (V)
E, = Non-input signal recorded level (V)
E, = Virgin tape noise output level (V)