NAD 1130 Bedienungsanleitung Seite 6

FRONT PANEL CONTROLS
1. POWER
Depress this button to switch on the pre-amplifier and
any equipment plugged into the SWITCHED convenience
outlet on the rear panel. To switch the power off, depress the
button again and release it.
if you prefer, you may leave the POWER switch perma-
nently engaged and use an external switch (such as a clock
timer) to turn the power on and off.
The preamplifier is equpped with a turn-on delay that
automatically mutes the preamp outputs for several seconds,
until the the preamp's circuits are fully stabilized. This
prevents the transmission of turn-on transients to the power
amplifier. The same circuit mutes the outputs instantly
when the power is switched off.
2. PHONES
Plug stereo headphones in here. The circuit will provide
proper drive signals for all conventional stereo headphones
regardless of their impedance, with just one exception:
electrostatic headphones usually are supplied with an adapt-
er unit which must be connected directly to the speaker
terminals on your power amplifier.
Insertion of a plug into the PHONES socket automati-
cally mutes the signal at the normal PREAMP OUTPUT
jacks, thus shutting off the loudspeakers. In order to resume
listening to loudspeakers you must unplug the headphones
from the PHONES socket.
You may freely use headphone extension cables. If you
want to use a headphone Y-connector to drive two headsets
simultaneously, they should be identical models. Connecting
together two headphones that differ widely in impedance
usually will produce a substantial loss of volume in the
headset having the higher impedance (or in both).
3. BASS
The Bass control adjusts the relative level of the low
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 knob to the right (clockwise) in-
creases 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.
4. 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 Trebie roll-off will make the sound dull.
5. BASS EQ.
This circuit boosts the lowest bass frequencies, those
below 60 Hz. In virtually all loudspeakers the useful output
rolis off at frequencies below the woofer/cabinet resonance
(which typically occurs between 40 and 70 Hz). The BASS
EQ 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:
* It helps to correct the rolled-off bass in some recordings.
+ It provides effective "loudness compensation" to re-
store subjectively correct tonal balance at low volume levels.
+ 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
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 smailer 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.
6. 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
vibratioris 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 infrasonic filter attenuates 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.
7. 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.
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