NAD 712 Manuel D'installation page 10

GB
Tape 2 for recording. (The TAPE 2 button must
remain engaged throughout
Disengaging the TAPE 1 MONITOR will break the
source signal path to TAPE 2 recorder's electronics.
To record from any other source, press the appro-
priate Input Select button. For example to copy the
soundtrack from a video onto an audio tape, select
the Video input. The selected signal will be fed to
both Tape 1 and Tape 2 for recording. By engaging
the Tape 1 Monitor you can hear the selected sound
as it passes through the Tape 1 recorder.
A note about copying: Tape copying is a conve-
nience intended for personal use. If you copy
commercially-produced recordings and sell or give
away the copies, you may be violating the copyright
or the property rights of the producer of the recording.
CAUTION: WHEN TAPE 2 IS SELECTED ONLY
ONE TAPE MACHINE SHOULD BE SET IN
RECORD MODE. IF BOTH ARE SET IN RECORD
MODE WITH TAPE 2 SELECTED, A FEEDBACK
LOOP RESULTS WHICH MAY CAUSE A LOUD
WHISTLE OR HOWL. SUCH FEEDBACK COULD
DAMAGE YOUR AMPLIFIER OR LOUDSPEAKERS.
CONNECTING A SIGNAL PROCESSOR TO
PRE-OUT AND MAIN-IN
The amplifier contains two independent sections or
stages: the control preamplifier (including the phono
preamp and most front-panel controls), and the power
amplifier (which provides the power to drive loud-
speakers). In normal operation the preamp and
power amp are connected together via factory-
installed U-shaped metal jumpers that bridge the
PRE-OUT and MAIN-IN jacks. Check to be sure that
they are fully inserted into the jacks and that nothing
is touching them.
By removing the metal jumpers (after first switching
OFF the POWER), you can connect various signal-
processing accessories in the path between preamp
and power amp: an equalizer, a surround-sound pro-
cessor, a stereo image enhancer, an electronic
crossover, etc. To use a signal processor, connect a
stereo patch cord from the PRE-OUT jacks to the pro-
cessor's line-level input jacks, and a second patch
cord from the processor's output jacks to the amplifi-
er's MAIN-IN jacks.
If you remove the metal jumpers, save them in case
you may want to disconnect the signal processor and
return to normal operation at a later time. If the
jumpers should be lost, a conventional stereo patch
cord can be used to connect PRE-OUT to MAIN-IN in
each channel.
WHY 12 O'CLOCK IS NOT ALWAYS THE
BEST BALANCE SETTING
Ideally the detented centre position of the Balance
control would be the normal setting. But several com-
mon circumstances may cause unequal balance,
requiring an off-centre setting of the Balance control
to restore the most uniform spread of stereo sound
between the speakers. These include unequal output
from the two channels of the phono cartridge, different
acoustical environments around the two loudspeak-
NAD
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ers, or simply a listening position that is closer to one
the recording). speaker than to the other. (In general, for the best
stereo imaging, your chair should be at precisely the
same distance from both speakers.)
Recordings often contain small errors in channel
balance, typically no more than 2 dB; but this is
enough to degrade stereo imaging. Small compen-
sating changes in the setting of the Balance control
can significantly improve the apparent depth and sta-
bility of the stereo image.
WIRING EXTRA SPEAKERS FOR AMBIENCE
A useful option for the SPEAKERS B terminals is to
connect a second pair of speakers wired for "ambi-
ence recovery,"
spaciousness of stereo recordings. Locate a pair of
small loudspeakers along the side walls of the listen-
ing room, slightly behind the main listening area and
as far as possible to the left and right. Often it is use-
ful to aim such speakers upward or toward the rear,
so that their sound reflects randomly off the walls
before reaching you.
From the (L+) red terminal in the "B" group, connect
a single wire to the positive terminal of the left-rear
speaker. Connect a similar wire from the (R+) red ter-
minal to the positive terminal of the right-rear speaker.
Make no connection to the black (L–) and (R–)
terminals on the amplifier; instead, connect a wire
from the negative terminal of the left-rear speaker to
the negative terminal of the right-rear speaker. Thus
wired, these rear speakers receive the left-minus-right
"difference" portion of the composite stereo signal.
If you have connected speakers this way, engage
SPEAKERS B when you want to hear spatially
enhanced surround-sound stereo. Disengage SPEAK-
ERS B to return to conventional two-speaker stereo.
A NOTE ON OVERLOAD PROTECTION
Because NAD amplifiers sound so clean and musi-
cal when driven beyond their nominal power ratings
and when used to drive low-impedance loudspeakers,
you may be tempted to stress your amplifier beyond
its design capacity. It can safely and cleanly drive
complex speaker impedances with wide-range musi-
cal signals whose peak level is 50 watts or more, but
it may overheat if called upon to deliver high power
CONTINUOUSLY into a low impedance.
Thus you may play music at volume levels that
cause the brief transient peaks and climaxes in music
to exceed the amplifier's rated power by a consider-
able margin. (With Soft Clipping the music will
continue to sound good at those high peak levels.)
But if you overdrive the amplifier continuously rather
than only on peaks, the output transistors may over-
heat.
This is particularly likely if you try to drive two pairs
of speakers, or speakers having a very low
impedance, at high volume levels. If the amplifier
stops playing, switch off the power for a few minutes
and allow the output stage to cool. If overheating was
the fault, the receiver will operate normally when it is
turned back on. But severe abuse of this type may
cause internal fuses to blow to protect the amplifier. If
the amplifier stops playing and the green Power LED
enhancing the apparent