Akai GX-260D

5. TOTAL HARMONIC DISTORTION
GX-260D
Audio Line
Frequency input Line
Oscillator
output
Distortion
Meter
Fig. 5
Connect the measuring instruments as shown in Fig. 5
and record a 1,000 Hz sine wave signal at “O” VU.
Playback the resultant signal and measure the over-
all distortion factor.
NOTE 1) At this time, Distortion of the Audio Fre-
quency Oscillator must be. sufficiently
small.
2) When measuring the distortion factor, new
tape should be used.
6. CROSS TALK (Cross talk between the tracks)
TAPE
Fwo. REV.
TAPE DIRECTION
!
2
TAPE DIRECTION, 3
4
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 play-
back the tape on track No. 3 and (1) (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.
2 Eo
C=20 log "EL -E, (dB)
where, C =Desired cross talk ratio (dB)
Eo =1,000 Hz signal output level (V) =a
E, =1,000 Hz cross talk level (V) ES
E, =Non-input cross talk level (V) _ EZZZ
7. ERASE RATIO
ban -
TAPE TAPE
4
2
77! ser
4
Fig. 7
As shown in Fig. 7, using a virgin tape, first record
a 1,000 Hz sinewave signal at +3 VU level, then
playback this recorded signal and take a V.T.V.M.
reading at the output level.
Next, erase this recorded portion and playback the
erased part through the B.P.F. (1,000 Hz sensitivity
1:1) and take readings of the erased signal. Obtain
a ratio between the two from the following formula:
= Eo
Er =20 log "ED —E, (dB)
where, Er =Desired erase ratio
E = 1,000 Hz signal output level (Vv)
E, =Erased 1,000 Hz signal and noise
level (V)
E, =Erased noise level (V)
NOTE: When measuring cross talk. and erase ratio
virgin tape should be used.