Marantz 3800 - Page 7

1-2
through the buffer amplifier circuit, TAPE
REC-EQ and DOLBY Switches. The input level
to the encoder/decoder is regulated by the
RECORD LEVEL Controls. The output of the
encoder/decoder is applied to the TAPE OUT-
PUT and DUBBING OUT Jacks. With the
DOLBY Switch set to OF F, the encoder/decoder
is bypassed and the high-level input signals are
applied directly to the TAPE OUTPUT and
DUBBING OUT Jacks. The encoder/decoder
functions as a flat amplifier, an encoder, or a
decoder depending on the position of the
DOLBY
Switch
(Figures
1-1
and
3-9).
The high-level input signals are concurrently
applied to the SCOPE OUTPUT Jacks and to the
Dolby decoder, through the TAPE MONITOR
Switch and PLAY CAL Controls. The decoder
functions as a flat amplifier, or a decoder, de-
pending on the position of the DOLBY Switch,
the TAPE MONITOR Switch, and the TAPE
COPY Switches (Figure 1-1). The output signal
of the decoder is monitored by the Dolby Level
VU Meter and applied to the MODE Switch.
The MODE Switch determines the manner in
which the left- and right-channel signals of the
program source are applied in the Model 3800:
LEFT channel only, RIGHT channel only, two-
channel STEREO, STEREO REVERSE, or
L+ R (left and right channels combined). The
signal selected by the MODE Switch is then
applied to the BALANCE Control. The
BALANCE Control adjusts the relative signal
level of the left and right channels by attenuating
the level of one channel while maintaining the
level of the other. From the BALANCE
Control, the signal is applied to the VOLUME
Control, which varies the level of the output
signal available at the PREAMPLIFIER OUT-
PUT Jacks.
The signal is also applied to the Loudness
Contour Circuit which, when activated, boosts
low and high frequencies at low listening levels
so that all frequencies appear to have equal
loudness. The Loudness Contour Circuit adjusts
the frequency response of the Model 3800 to
compare with the Fletcher-Munson loudness
curves (Section 2). The signal from the
VOLUME Control is then applied to the input
of the Times-Ten (X10) Amplifier Circuit.
The X10 Amplifier increases the signal level to
that required to drive power amplifiers. The
output of the X10 Amplifier is applied to an
Active Filter Network comprised of three filter
circuits (30Hz, 5KHz and 9KHz) and a Filter
Amplifier.
The
Active
Filter
Network
sharply
reduces
low-
and/or
high-frequency
noise
that
may
originate
at
the
program
source.
The
out-
put
of
the
Filter
Amplifier
is
then
applied
to
the
Tone
Control/Turnover
Network
(BASS,
MID
and
TREBLE
Tone
Controls),
the
250Hz
and
the
4KHz
TURNOVER
circuitry,
and
a
Tone
Amplifier
stage
(through
the
TAPE
REC-EQ
Switch).
The
output
of
the
Filter
Amplifier
after
TAPE
REC-EQ
is
also
applied
to
the
TONE DEFEAT Switch.
The
Tone
Control/Turnover
Network
performs
a
dual
function:
the
tone
control
portion
of
the
network
boosts
or
attenuates
low,
middle
and
high
frequencies;
the
turnover
portion
of
the
network,
when
activated,
decreases
the
point
at
which
low
frequencies
are
affected
by
the
BASS
Control
(250Hz)
and
increases
the
point
at
which
high
frequencies
are
affected
by
the
TREBLE
Control
(4KHz).
The
TONE
DEFEAT
Switch
selects
either
the
flat
output
of
the
Filter
Amplifier
(bypassing
the
tone
controls)
or
the
tone-control-altered
output
of
the
Tone
Amplifier.
From
the
TONE:
DEFEAT
Switch,
the
signal
is
applied
to
the
Time
Delay
Relay.
The
circuit
associated
with
the
Time Delay
Relay
holds.the
relay
contacts
open
for
approx-
imately
five
seconds
after
power
is
appied
to
the
Model
3800.
After
the
power
supply
circuits
have
stabilized,
the
relay
contacts
close.
Audible
“pops”
that
may
arise
from
p
ower
supply
transients
are
thereby
eliminated.
From the relay contacts the signal is appied to
the PREAMPLIFIER OUTPUT Jacks and con-
nected to drive an external power aml ifier.
The
power
amplifier
outputs
are
connecied
to
the
SPEAKER
SWITCHING
INPUTS
Terminals
and
the
signal
is
applied
to
the
stereo
PHD
NES