Advertisement
CIRCUIT DESCRIPTION
2. WOW/FLUTTER
MEASUREMENT
CIRCUIT
Wow /flutter measurement
circuit
The output signal from the Schmitt trigger circuit is input
to an one shot multivibrator (or mono-stable multivibrator
IC4) as trigger pulse. It passes through a differentiation cir-
cuit consisting of capacitor C16 and resistor R47 after in-
version by D16 into negative-polarity signal.
The trigger pulse width is determined by the following rela-
tionship between
an input center frequency and passive
devices.
Input center frequency = 3 kHz (JIS, NAB, and CCIR): VR4,
R51, and C18
Input center frequency
= 3.15kHz (DIN): VR5, R52, and
C18
The output from the IC4 is converted into +-15V square-
wave signals by transistors Q10, Q11, and Q12 and then
input to the low-pass filter (IC5). However, the RL4 relay
circuit becomes inactive if the input signal outside of the
measurement range is detected or this product is selected
as the frequency counter by select switch S3b. As a result,
the meter function does not work because the signal blocks
following the IC5 are electronically disconnected from the
unit system.
The low-pass filter made of the IC5 is a three-order multiple-
feedback butterworth filter. Its cut-off frequency is 300 Hz
(-3 dB) and its attenuation factor is-18 dB/OCT. This filter
attenuates the input signal if it is higher than 300 Hz.
If this product receives the signals from external circuits such
as a tape recorder and the signals contain wows/flutter
characteristics, wow/flutter frequencies can be reproduced
in the range of DC and 300 Hz.
Variable resistor VR6 is provided for offset adjustment of
the IC5.
Variable resistor VR4 is provided to adjust the TP8 direct
output into 'OV' if the input center frequency (single sine
wave
signal) is 3kHz (JIS, NAB, and CCIR).
Variable resistor VR5 is provided to adjust the TP8 direct
output into '0 V' if the input center frequency (single sine
wave
signal) is 3.15 kHz (DIN).
The output from the IC5 is also transmitted to an external
circuit. Its output voltage per frequency drift 1% is 1 Vdc
at the output impedance of 600 ohm.
The wow/flutter signals reproduced by the IC5 (low pass
filter) is input to the S1 attenuator unit (X75-1110-00). In
this unit, the full scale adjustment for each range can be
made
with variable resistors VR301
to VR305.
The output from the attenuator unit is input to the low-pass
filter (IC6). Harmonic components higher than 3 kHz can be
completely eliminated in this pass filter. This low-pass filter
is the same type as that of the IC5 low pass filter. Its cut-
off frequency is 200 H.
The output from the IC6 low-pass filter is selectively input
to one of the WTD, WOW,
FLUTTER, and UNWTD
filters
by select switch S2 of the function unit (X69-1000-00). Vari-
able resistors VR7, VR8 and VRQ are provided as level set-
ting adjusters based on WTD.
The signal selected by select switch S2 is transferred to the
IC7 buffer amplifier through its corresponding filter. Then,
it is input to one of the four high-pass filters. These four high-
pass filters correspond to the four standards (JIS, NAB, CCIR
and DIN). Select switch $4 is provided on the indication unit
(X69-1010-00) to select one of the four high pass filters.
The output from the selected high-pass filter is then input
to the meter amplifier made up of iC8 and ICQ. Variable resis-
tors VR11
to VR14 are used as level setting adjustments
based on JIS (VR11).
The signal selected by select switch S4 is input to IC8 and
ICQ. If the range selected by S1 is 0.003% to 1%, that sig-
nal is amplified
+26 dB.
It is amplified
+6 dB in the
3%-10%
range.
Variable resistor VR15
is provided for IC9 offset adjustment.
The output from the ICQ is transmitted to an external cir-
cuit. Its output voltage per meter full scale is 3 Vrms at an
output impedance of 600 ohm. The output is also input to
the X69-1010-00 indication unit and then sent to the cor-
responding detector.
(1) JIS standard detector circuit
The signal from the X69-1010-00 indication unit is input to
the IC10 absolute amplifier and then rectified at full-wave
level. This rectified signal is then sent to the smoothing cir-
cuit consisting of R93, C44, R94, and C45 through the in-
dication unit. The smoothing circuit converts the input signal
into a DC signal. This DC signal is input to the indication unit
again and then drives the meter. Note that the meter indi-
cates the effective values.
Variable resistor VR16 can be used as a peak adjustment
of the signal waveforms output from the IC 10 absolute am-
plifier.
(2) NAB standard detector circuit
The signal from the X69-1010-00 indication unit is input to
the IC 10 absolute amplifier and then drives the meter through
R306. Note that the meter indicates the average values.
(3) CCIR/DIN standard detector circuit
The signal from the X69-1010-00 indication unit is detect-
ed by the IC11 peak detector and then input to the indica-
tion unit. It then drives the meter.
Note that the meter
indicates peak values.
Variable resistors VR17, VR18 and VR19 can be used as
time-constant adjustments in the following manner:
VR17:
Time constant adjustment for plus charge
VR18: Time constant adjustment for minus charge
VR19: Time constant adjustment for discharging
Meter output circuit
The IC12 and IC13 are amplifiers which generate the DC out-
put from the values indicated by the meter.
The meter signal value is indicated by the two outputs from
both ends of the meter. The signal is input to the IC 12 buffer
amplifier and then transmitted to the IC 13 differential am-
plifier (1/2). This differential amplifier has an unbalanced out-
put circuit. The output from this unbalanced output circuit
is then input to the 1C13 (2/2) amplifier and amplified to a
level where an its output of 1Vdc per meter full scale is pos-
sible. The output from the 1C13 amplifier is transferred to
an external circuit as the RECORDER
OUT signal. Its
output impedance is 600 ohm.
Variable resistors VR20, VR21
and VR22 are used as ad-
justments in the following manner:
Advertisement
