Akai 4400D Service Manual

5. TOTAL HARMONIC DISTORTION
FACTOR
4400
Audio Line
Frequency ATT, 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 “0” VU.
Playback the resultant signal and measure the over-
al] distortion factor. Measure the noise level of the
tape recorder without the tape. Connect the Audio
Frequency Oscillator directly to the distortion meter
for measurement of the distortion factor of the
oscillator. The required distortion factor can be
obtained from the results of the above measurement
by the following formula:
dy =d—d, - 4,
where, do = Required distortion factor
d = Overall distortion factor
” dy = Noise level
d, = Distortion factor of the oscillator
NOTE: When measuring the distortion factor, new
tape should be used.
6. CROSS TALK
(Cross talk between the tracks)
(TAPE)
mmm TAPE DIRECTION
®@@O
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 through the B.P.F.
(band pass filter sensitivity . .. 1:1) and obtain a
ratio between the two from the following formula:
C= 200g — Eo _ (ap)
2 Ey
where, C = Desired cross talk ratio (dB)
E ,000 Hz signal cutput level
E, = 1,000 Hz cross talk level
E, = Non-input signal recorded level
7. ERASE RATIO
‘As shown in Fig. 4, connect a High Sensitivity
V.T.VM, to the Line Output of Model 4400. Play-
back 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 dB, 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 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
= ——2___ (dB.
Er = 20 log: BE, (dB)
where, Er = Desired erase ratio (dB)
E,= 1,000 Hz signal output level
E, = Non-input signal recorded level
E, = Virgin tape noise output level
8. POWER OUTPUT (4400 only)
4400 82. “High
Speaker Sensitivity
output V.T.V.M.
Fig. 7
As shown in Fig. 7, connect an 8Q dummy load
resistor to the speaker output of the recorder and
connect this terminal to a High Sensitivity V.T.V.M.
Playback a 250 Hz “O” 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
results of the above measurement by using the follow-
ing formula:
=. EB
aM)
where, P= Desired power output (watts)
E= Measured voltage (R.M.S.)
R= 82

Akai 4400D Specifications

General

Brand	Akai
Model	4400D
Category	Tape Deck
Language	English