Akai M8

I
HOW
TO
MEASURE
DESIGNATED
VALUES
IN
SPECIFICATIONS
TAPE SPEED TOTAL HARMONIC
DEVIATION:
Record
the
1,000
cps.
sine
curve
of
DISTORTION
the
tape
speed
at
rating
speeds
with
FACTOR:
Provide
the
input
terminal
of
the
a standard sound recorder (AMPEX
351A, for instance) which is little af-
fected by the tape speed deviation
throughout the whole length of the
tape. Put this standard tape on the
tape recorder under test for playing
back, and measure its output by a
counter, then convert the value into
rating power frequency to evaluate
the tape speed deviation.
For a rough measurement, the tape
speed deviation can also be measured
with a speed test timing tape by the
count on a stop watch.
lested
recorder
with
1,000
cps.
sine
curve
signals
and
record
these
signals
on
a
recording
tape
at
the
zero
level
on
the
recorder‘s
internal
VU
meter.
Then
playback
the
signals
under
the
normal
recording
condition
to
meas-
ure
the
distortion
factor
by
an
oscil-
lator.
Remove
the
recording
tape
from
the
recorder,
then
read
the
noise
level
on
tne
oscillator
to
get
the
required
distortion
factor
by
the
following
formula:
dO=d—dli—d2
dO...required
d...overall distortion factor
dl...noise levei
d2...distortion
factor
of
the
oscilla-
tor used
NOISE:
Playback
the
sine
curve,
250
cps.
that guarantees wow and flutter wiih-
tape. recorded on a glanclard record-
in 0.07 per cent, and read the effec-
tive
value
on
wow
meter
er
on
the
tested
recorder
to
measure
Since
the
sensibility
of
wow
and
the
voltage.
flutter
frequency
below
2cps.
and
Remove
the
tape,
then
measure
the
ahove
5cps.
drops,
the
frequency
noise
level
under
the
same
condition,
over
Scps.
is
put
to
3
db/OCT
cir-
cuit,
and
the
frequency
below
2
eps.
is
put
to
6
db/OCT
circuit
for
adjust-
ment.
This
adjusted
value
is
called
OUTPUT
:
Playback
on
the
test
recorder
the
auditory
compensated
value.
Calculate the ratio betw2en the two
in decibel.
WOW AND
FLUTTER:
Playback
the
3,000
cps.
standard
tape
SIGNAL
TO
1,000 cps. sine curve tape which was
reccrded at the zero VU level on a
standard recerder. Terminate the
test recorder with eight ohnis.
Square the voltaye reading, then
FREQUENCY
divide
the
figure
by
eight
ohms
to
RESPONSE: Connect to the input terminal of the
(OVERALL FREQU- test recorder a sweep frequency of
ENCY
RESPONSE)
the
level-20
db.
Record
the
sweep
CROSS
TALK
:
Record
1,000
cps.
signal
at
+3
VU
get the rms. power output.
signal, playback the tape, terminate
the output with eight ohms.
Read the frequency response which
should have a maximum deviation
of 6 db.
te
en the third track, then playback
this signal thru a 1,000cps. Band
Pass Filter.
Compare the output of tracks 1 and
2 in decibels.