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to adjust the loudness level
in
the headphones with no fear
of overdriving the speakers or disturbing neighbors.
If you have connected an adapter unit for electrostatic
headphones to the SPEAKERS B terminals, you can use the
SPEAKERS selector to switch between your main stereo
speakers (A) and the headphones (B).
If
you have connected speakers wired for "ambience
recovery" to the SPEAKERS B terminals, you can use the
SPEAKERS selector to listen to conventional stereo
(A), to
switch off the main speakers and listen only to the stereo
L-minus-R "difference" signal
in
the rear speakers (B), or to
listen to spatially enhanced stereo (A +
B)
.
You
will find that
the stereo difference signal
is
usually lacking
in
bass.
If
the difference signal
is
very weak, the recording lacks
stereo separation.
4. BASS
The Bass control adjusts the relative level of the low
frequencies
in
the sound. The electrical response of the
amplifier
is
flattest when the control
is
set
in
the detent at the
12
o'clock position. Rotation of the knob to the right (clock-
wise) increases the level of low-frequency sounds, and
rotation counter-clockwise decreases their level. Adjust the
Bass control to achieve the tonal balance that sounds most
natural to you.
At moderate rotations away from center the effect of the
Bass control
is
subtle, because its action
is
confined to the
lowest audible frequencies where significant energy is sel-
dom found
in
recordings. Only at large rotations away from
center
is
there a substantial boost or cut at the mid-bass
frequencies that are common
in
music.
5.
TREBLE
The Treble control adjusts the relative level of the high
frequencies
in
the sound. The response of the amplifier
is
flattest when the control
is
set
in
the detent at the
12
o'clock
position. Rotation of the Treble control to the right (clockwise)
increases the level of high-frequency sounds, and rotation
counter-clockwise decreases their level. Adjust the Treble
control to achieve the tonal balance that sounds most
natural to you .
Boosting the Treble increases the brilliance and clarity of
details
in
the sound, but also makes any noise more promi-
nent. Turning down the Treble makes the sound mellower
while suppressing hiss and record surface noise; but too
much Treble roll-off will make the sound dull.
6. BASS EQ
This circuit boosts the lowest bass frequencies, those
below 60 Hz.
In
virtually all loudspeakers the useful output
rolls off at frequencies below the woofer/cabinet resonance
(which typically occurs between 40 and 70 Hz). The BASS
ECJ.
circuit compensates for this rolloff, extending the useful
response of the speakers significantly lower
in
frequency.
If
your loudspeakers already have extended and
powerful deep-bass response, the BASS
EQ
provides
other benefits:
â–¡
It
helps to correct the rolled-off bass
in
some recordings.
â–¡
It
provides effective "loudness compensation" to re-
store subjectively correct tonal balance at low volume levels.
â–¡
It
helps to compensate for listening-room acoustics.
("Standing waves"
in
the room tend to weaken the low bass
and reinforce the mid-bass at typical listening positions.)
Of course very low frequencies are not found
in
all
music, nor
in
all recordings, so the effect of the BASS
EQ
often won't be obvious. Sometimes you may find that switch-
ing
it
in
and out does not produce any apparent change
in
the sound, simply because the recording contains no energy
at very low frequencies. But usually the BASS EQ will
7
provide an audible (and occasionally a dramatic) strengthen-
ing of the deepest bass.
The BASS EQ circuit also includes
an
infrasonic filter
that rolls off the response below 25 Hz to prevent inappro-
priate amplification of non-musical signals below the
audio range.
CAUTION:
Be
prepared to switch off the equalization
when playing recordings (especially digitally mastered discs)
that contain unusually powerful recorded bass. The combi-
nation of a high playback volume level, the BASS
EQ
, and
a bass-heavy input signal could overdrive the amplifier into
clipping
and-more
important-overdrive
your woofers
beyond their safe excursion limits, causing the voice-coils
to clatter against the magnet back-plates. (This risk
is
par-
ticularly serious with small woofers, those smaller than six
inches
in
diameter, which usually are not designed to accept
high power levels at the lowest frequencies.) As long as a
speaker sounds good
it
probably
is
OK; but distorted or
unmusical sounds, such as clattering or buzzing, signal
distress
in
a woofer.
Be alert, also, for signs of acoustic feedback
(in
which
the low-frequency vibrations from the speakers are picked
up by the record-playing stylus and are re-amplified). If you
encounter a sustained low-frequency roar, or frequent
groove-jumping, immediately turn down the Volume and
switch off the BASS
EQ
until a more nearly vibration-free
mounting for the turntable
is
found.
7.
INFRASONIC
FILTER DEFEAT
The output from a record player usually contains strong
but inaudible impulses at infrasonic frequencies (below
20 Hz) due to disc warps, stylus/tonearm resonance, and
vibrations reaching the turntable. If these are amplified at
full strength, they may waste amplifier power and produce
excessive woofer cone excursions, muddying the sound.
The amplifier contains an infrasonic filter to attenuate
these unwanted signals. The filter
is
normally in-circuit -
(with the button OUT), and
it
is
especially desirable to have
it
in-circuit when a large low-frequency boost
is
being
applied via the BASS control.
If
you want to bypass the infrasonic filter, depress the
INFRA DEFEAT button. As long as the button
is
OUT,
the
filter
is
active.
A second infrasonic filter
is
included
in
the BASS
EQ
circuit and
is
automatically engaged when the bass equaliza-
tion
is
used.
It
is
not affected by the INFRA DEFEAT button.
8.
MONO
This button blends the two stereo channels together to
produce monophonic sound. This blend minimizes rumble
and surface noise
in
old monophonic records. The button
must
be
OUT for normal stereo listening.
The MONO button also disables the stereo
FM
circuits
in
the tuner. Normally the tuner receives monophonic trans-
missions
in
mono and automatically switches on its multiplex
decoding circuits when a stereo
FM
broadcast
is
received
(as shown by the
FM
STEREO indicator). But when a very
weak
FM
stereo signal is received, it may be excessively
noisy because of the multiplex encoding technique used for
stereo broadcasting.
In
that case, depress the MONO button
to lock the tuner
in
the mono mode,
in
order to obtain
consistently quieter and cleaner sound.
Remember to disengage the
MONO button when you
re-tune to a stronger signa
l.
As long as the MONO button
is engaged,
no
broadcasts can be received
in
stereo.
9. DYN
SEP
DEFEAT
The tuner contains a "dynamic separation" circuit that
reduces noise
in
weak
FM
stereo signals by selectively
reducing the high-frequency stereo separation at times when
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