Teac A-650 - Performance Measurement Details; Dolby NR Effect Measurement; Peak Limiter Efficiency Checks

7.
10.
8.
11.
6-4-7. DOLBY NR EFFECT MEASUREMENT
Preparations:
Connection. See Fig. 6-11 on page 25.
Switch Setting:
EQ
LIMITER DOLBY NR
BIAS
OUT OUT
1
I OUT
5.
7.
6.
6-4-8. PEAK LIMITER EFFICIENCY CHECKS
Preparations:
Specification: Limiter efficiency: 7dB±2dB
Connection: See Fig. 6-11 on page 25.
Switch Setting.
DOLBY NR
LIMITER
BIAS
EQ
OUT
OUT
3 3
OUT
5.
6.
7.
9.
8.
29
3.
4.
1.
2.
Load a TEAC MTT-501 test tape.
Apply and record a 400 Hz signal at — 12 dB (194 mV)
for several seconds.
Set LIMITER switch to IN.
Apply and record a 400 Hz signal at — 2 dB (615 mV)
to next portion of the tape for a while.
Rewind the tape to the starting point of the 400 Hz,
-12 dB signal recorded portion.
Play the tape and compare the output level difference
between the — 12 dB recorded portion and the — 2 dB
recorded section.
The output level of — 2 dB recorded portion should be
3 dB ± 2 dB higher than that of the -12 dB recorded
portion.
Thus, when a — 2 dB input level is applied with LIM 
ITER switch IN, Peak Limiter circuit functions to
Load a TEAC MTT-505B test tape.
Apply and record a 1 kHz signal at -42 dB (6.1 5 mV).
Rewind and play this recorded section.
While playing the 1 kHz signal, read the indication of
the output level on the VTVM with the DOLBY NR
1N-0UT-IN/MPX switch at IN and OUT positions.
The output level should vary 4 dB to 7 dB between
the IN and OUT positions. (The output level in the IN
position should be lower than the OUT position.)
Repeat the above procedure changing the applied test
signal to 10 kHz at -39 dB (8.69 mV).
Control Setting:
OUTPUT: Specified Setting (See 6-2-2)
Specified Setting (See 6-3-2)
Minimum Setting
reduce playback level to7dB±2dB compared to the
direct record-playback level (unlimited recording level).
This 7 dB ± 2 dB corresponds to Specified Limiter
Efficiency.
The variation should be 8 dB to 12 dB. (Tire outpul
level in the IN position should be lower than in the
OUT position).
Repeat the preceding “ CrO 2 TAPE" procedure, except
use the TEAC MTT-501 test tape and set BIAS/EQ
switches to “ 3 ” position.
The VTVM should indicate -49 dB minimum (2.74
mV maximum).
This — 49 dB corresponds to the specified signal-to-
noise ratio of 44 dB (minimum): the difference be 
tween the residual noise of -49 dB and the specified
output level — 5 dB.
LINE:
MIC:
LINE:
MIC:
Fe-Cr TAPE
Repeat the preceding procedure, except use the TEAC
MTT-504 test tape and set BIAS/EQ switches to “ 2"
position.
Requirement is the same as that for “ CrO? TAPE".
Control Setting:
OUTPUT: Specified Setting (See 6-2-2)
Specified Setting (See 6-3-2)
Minimum Setting
Hi-Fi TAPE
9.
CrO 2 TAPE
1.
2.
3.
4.
Specifications:
Variation from reference at 1 kHz: 4 dB to 7 dB
Variation from reference at 10 kHz: 8dBto 12 dB