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Akai 4000DS Mk-II Service Manual

Akai 4000DS Mk-II
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5.
TOTAL
HARMONIC
DISTORTION
FACTOR
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
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
oscilla¬
tor.
The
required
distortion
factor
can
be
obtained
from
the
results
of
the
above
measurement
by
the
following
formula:
do
=
d
-
dj
-
d2
where,
do
-
Required
distortion
factor
d
-
Overall
distortion
factor
d|
-
Noise
level
d
2
-
Distortion
factor
of
the
oscillator
NOTE:
When
measuring
the
distortion
factor,
new
tape
should
be
used.
7.
ERASE
RATIO
As
shown
in
Fig.
4,
connect
a
High
Sensitivity
V.T.V.M.
to
(he
Line
Output
of
Model
4000DS.
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
dB,
then
playback
this
recorded
signal
and
tape
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:
Er
=
20
log
^
(dB)
Where,
Er
-
Desired
erase
ratio
(dB)
Ep-
1,000
Hz
signal
output
level
E
2
—
Non-input
signal
recorded
level
E|
-
Virgin
tape
noise
output
level
6.
CROSS
TALK
(Cross
talk
between
the
tracks)
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
=
20
log
(dB)
where,
C
-
Desired
cross
talk
ratio
(dB)
Eq
-
1,000
Hz
signal
output
level
E
2
-
1,000
Hz
cross
talk
level
El
-
Non-input
signal
recorded
level

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Akai 4000DS Mk-II Specifications

General IconGeneral
TypeReel to Reel
Track System4-track, 2-channel, stereo/monaural system
Signal to Noise Ratio50dB
Reel SizeUp to 7 inch reel
Total Harmonic Distortion1.5%
Output0.775V (line)
Tape Speed3.75 & 7.5 ips
Heads1 x erase
Input Sensitivity50mV (line)
Semiconductors6 x Transistors
InputsLine
OutputsLine

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