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Technics SH-8075 - TECHNICAL INFORMATION; VARIABLE EQUALIZER CIRCUIT; BAND LEVEL CONTROL CIRCUIT

Technics SH-8075
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SH-8075
@
TECHNICAL
INFORMATION
@
Variable
equalizer
circuit
(for
varying
the
center
frequency
and
band
width)
Integrator
Integrator
|
Adder/Subtractor
The
band
pass
filter
of
this
unit
is
designed
so
that
the
resonance
peak
characteristic
(band
width:
Q)
is
constant
at
5.
With
the
variable
equalizer
switch
set
at
“on”,
the
center
frequency
and
resonance
peak
characteristic,
only
for
20
Hz
~
400
Hz,
and
the
frequency
band
level
as
well
as
the
other
band
level
can
be
varied.
-
Fig.
1
is
a
variable
equalizer
circuit
consisting
of
3
operation
amplifiers
(1
adder/subtractor
and
2
integrators).
The
center
frequency
(fo)
of
band
pass
*
Band
ievel
is
at
+12
dB.
filter
is
determined
by
the
time
constant
of
R
and
C,
:
e
pay
ee
A
and
the
frequency
is
varied
by
double-acting
volume
poodle!
preauency
(fo)
Bandwidth
(Q)
varies
by
r.
R.
The
resonance
peak
characteristic
is
varied
by
:
double-acting
volume
r.
.
Fig.
1
©
Band
level
control
circuit
|
(for
varying
the
center
frequen):
by
#12
dB)
abe
Loe
eae
ss
*
¥
Fig.
2
is
a
circuit
that
‘ibs
the
frequency
charac:
eee
teristic
of
peak
anddip.
a
When
the
band
level
control
volume.
is
at
middle
position
@,
BPF
is
off
the
circuit,
therefore
the
input/output
gain
(G)
is
as
follows:
As
VR
is
shifted
t
to
0
®.
i
input
Gon
R3
and
output
of
(ore
cer
BPF
are
added
as
the
output
to
give
the
following:
.
or
a
Shifted
from
@—-@
R.,
_
(Peak
characteristic)
(=7+4
aT)
G=
Band
leval
control.
Tg
:
gain
characteristic
of
BPF
As
VR
is
shifted
to
©,
synthesized
NFB
of
BPF
and
Fig.
2
R2
is
given,
thereby
making
a
frequency
characteris-
tic
having
a
dip.
Response
of
bandwidth
contro!
(Q)
Definition
ne
|
|
|
INN
|
oN
ZING
“NA
.
“nq
expresses
the
sharpness
of
~
the
peak
and
the
dip,
and
its
value
is
expressed
as
the
value
Steere!
a
ary
obtained”
“when”
the’
“center
9
aOR
Se
sete:
frequency
(fo)
is
decreased
by
3
06
less
than
the
peak
point
(the
dip
point
is
increased
by
3
dB),
and
is
divided
by
the
frequency
range(Af
=
f,
—
f,).
fo
:
Af

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