Teac A-4070G - Page 27

SIGNAL TO NOISE RATIO
PLAYBACK ————————____________
NO
OVERALL
Duo fwN FE
IMPORTANT
OUTPUT control should be at specified output level. The
signal to noise ratio must meet factory standards. The
values
given
are
obtained
using
an
unweighted
level
meter
while
the
supply
and
take-up
motors
have
voltage
applied
but
are
not
rotating.
The
values
are
with
reference
to
a
3% THD peak recording level.
Thread
a
tape
on
the
unit,
leaving
the
tape
outside
the
capstan
and
pinch
roller.
Place
the
unit
in
the
PLAY
mode
(
B
)
(the
tape
will
not
move).
The
level
meter
connected
to
the
LINE
OUT
jacks
should
indicate
-56 dB
or
less.
This corresponds to a signal Me oe. OW. ¥ v
to noise ratio of 48 dB(dif- CO rene ens TAPE DYNAMIC RANGE UN 48)
ference between residual noise ae ° a
-56 dB and specified output o—-2 4a— > 8
level ~8 dB for 1% THD). SBap re oo se ee SSEarEF ERAS Sidon sean p |
(REFERENCE)
For a 3% THD signal to noise
ratio, 6 dB is added, giving
54 dB(3Z% THD is 6 dB above 1%
THD level).
‘UV3NIT
OlLWY ASION O1 TWNOIS
54dB -56aB
Signal/Noise Computation
WHEN LEVEL METER
NOISE READS D-9-1
IMPORTANT
Clean and demagnetize the heads before proceeding. It is ex-
tremely important that all tests described in the proceeding
paragraphs have been completed and that all controls adjusted
are left unalterd.
Thread a record test tape (Scotch 203) on the unit.
Remove the AF oscillator from the LINE IN jacks.
Place the unit in the RECORD mode with no signal applied.
Note the point on the index counter where recording begins.
Rewind the tape and play it back.
The noise level as indicated on the level meter should be -54 dB
or less.
NOTE
Bias, erase and playback amplifier noise are all included
‘in this measurement.
All frequencies between 40 Hz and 15 kHz are measured un-
weighted.