Technics SH-8075 EH

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