Sony ICF-7800 - Page 4

CF-7800
(2) Tone Control
An NF (Negative Feedback) type where the
VOLUME controls the amount of feedback. Bass
and
treble
emphasis
are
more
pronounced
when
the
VOLUME is at a lower setting.
VR1 (BASS)
Due to the effect of C59, the impedance across
© and ®) in Fig. 1-3 is low at high frequencies .
and
high
at
low
frequencies.
Therefore,
the
low
frequencies
feedback
signals
are
emphasized
at
©
but
de-emphasized
at
©).
Consequently,
if the
VRI
slider
is
shifted
in
the
direction
of
©,
the
amount
of
low
frequency
feedback
will
increase,
thus
reducing
the
amount
of
bass
in
the
sound.
If,
however,
the
slider
is
shifted
in
the
direction
of
©,
the
amount
of
feedback
is
reduced
and
the
VR3
output
level
is
increased.
So
the
low
frequencies
in
the
IC7
output
are
emphasized.
VR2 (TREBLE)
High
frequencies
are
better
able
to
pass
through
C61
than
low
frequencies.
So
the
VR2
(TREBLE)
action
controls
the
high
frequencies
in
the
IC7
input
signals.
When
the
VR2
slider
in
Fig.
1-3
is
shifted
in
the
direction
of
®,
the
amount
of
high
frequency
negative
feedback
is
increased
while
the
signal
level
of
the
VR3
(VOLUME)
output
is
reduced.
So
the
IC7
output
will
be
low
in
high
frequency
signals.
But
when
the
slider
is
shifted
in
the
direction
of
(D),
the
amount
of
negative
feedback
of
high
frequency
signals
is
reduced,
and
the
VR3
output
signal
is
increased,
resulting
in
an
emphasis
of
the
high
frequencies
in
the
IC7
output.
VR3 (VOLUME)
The
IC7
input
signal
level
is
increased
when
the
VR3
slider
is
shifted
in
the
direction
of
@.
The
impedance
across
the
TONE
control
(VR1
and
VR2)
to
ground
portion
is
consequently
increased,
reducing
the
relative
proportion
of
impedance
due
to
C59
and
C61,and
thus
the
relative
effect
of
the
TONE
control.
But
when
the
VR3
slider
is
shifted
in
the
direction
of
(A),
the
effect
of
the
TONE
control
is
increased,
producing
a
kind
of
loudness
effect.
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