I
and connect its cable shield to the Ground (G) terminal. But
the better approach is to install a connector on the coaxial
cable, and plug it into the 750 socket.
The antenna terminals are connected to the FM tuner
circuit through an internal "balun" transformer that allows the
use of either a "balanced" 300-ohm twin-lead antenna cable
(connected to the two 3000 terminals) or an "unbalanced"
75-ohm coaxial cable (with its center conductor connected
to one of the 3000 terminals and the cable shield connected
to the Ground (G) terminal. However, a slight signal loss
can occur in such a transformer. The 750 coaxial socket is
connected directly to the FM tuner circuit, bypassing the
transformer, and so this is the preferred input when the best
possible input sensitivity is required.
4. PHONO INPUT. Plug the signal cables from your
turntable into these jacks. If the cables or plugs are color-
coded, refer to your turntable's instruction manual to learn
which cable or plug is for the Left channel (upper jack) and
which for the Right (lower jack). Be careful to insert each plug
fully into the socket so that the plug's metal skirt fits tightly
over the exterior of the socket. If necessary, crimp the plug's
metal skirt slightly so as to obtain a tight fit with the socket.
5. PHONO GROUND. If your turntable is equipped
with a grounding wire (usually a green wire terminating in
a U-shaped spade lug), connect it to this terminal. Turn the
thumb-nut counter-clockwise, place the spade lug under the
nut, and tighten the thumb-nut clockwise to secure the lug.
If the grounding wire has no terminal lug, strip off a half-inch
(1 to 2 em) of insulation to expose the bare wire, twist the wire
strands tightly together, insert the wire through the small hole
in the shaft of the Ground terminal, and tighten the thumb-nut
to fasten the wire in place.
If you encounter a persistent low-level hum or buzz in
the sound, connect a wire from the Ground terminal to a true
earth-ground, i.e., a copper-plated rod driven several feet into
the earth. A substitute electrical ground may also prove effec-
tive: a cold-water pipe, a steam radiator, or the third hole of a
modern electrical wall socket.
6. MM/MC PHONO SELECTOR. This switch sets the in-
put sensitivity and gain of the phono preamplifier circuit. Set it
according to the output level of your phono pickup cartridge.
Set the switch at MM for cartridges of the moving magnet,
induced magnet, moving flux, and moving iron (variable flux)
types, and for "high output" moving-coil pickups, i.e., those
with a rated output of 1.0 mV or greater. If your cartridge is a
low-output moving-coil pickup (with a rated output less than
1.0 mV), set the switch at MC.
Here is another way to determine the correct setting of
the MM/MC switch. Begin by setting it to MM. After you have
completed the installation and wiring of the receiver, playa
record. You should obtain a satisfyingly loud volume level at
VOLUME control settings between 9 o'clock and 3 o'clock. If
you have to turn up the VOLUME control beyond 3 o'clock to
get adequately loud sound, turn the volume back down and
re-set the MM/MC switch to MC.
7. CD INPUT. Connect the audio signal cables from a
digital Compact Disc player to these jacks. The input signal
will be fed to the VOLUME control before reaching any active
circuitry, so the amplifier's circuits cannot be overloaded by
high-level signals from the digital player.
If you don't have a CD player, any other line-level signal
source (such as a spare tape deck) may be connected to the
CD input.
8. AUX INPUT. These auxiliary jacks are for any "line
level" signal source, such as a spare tape deck, the audio line
output from a videocassette or videodisc player, or a television
sound tuner. As with all of the other input/output jacks on this
amplifier, the upper jack in each pair is for the Left channel
and the lower jack is for the Right channel.
4
9. TAPE REC/PLAY. The tape connections may be used
with recorders of all types: cassette, micro-cassette, open-
reel, digital, etc. To make recordings, connect a stereo patch
cord from the amplifier's TAPE OUT (RECording) jacks to the
recorder's LINE INPUT jacks (not to its microphone inputs).
To play back tapes, connect a stereo patch cord from the
recorder's LINE OUTPUT jacks to the amplifier's TAPE IN
(PLAYback) input jacks.
The TAPE REC/PLAY jacks may be used for connecting a
signal-processing accessory instead of a tape recorder. Exam-
ples of such accessories include a dynamic range processor, a
dynamic noise filter, a DBX disc decoder, or any other device
whose operation depends on the setting of a signal threshold.
Connect a patch cord from the TAPE OUT (REC) jacks to the
processor's inputs, and another patch cord from the proces-
sor's outputs to the TAPE IN (PLAY) jacks.
Other signal processing accessories, such as a graphic
equalizer or the special equalizer supplied with some loud-
speakers, may be connected either to the TAPE jacks or at the
Preamp Out jacks. The choice is a matter of convenience.
10. PREAMP OUT, MAIN IN. Each channel of the ampli-
fier is composed of 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 loudspeakers). 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 the jumpers 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 time-delay ambience reproducer, a stereo image
enhancer, an electronic crossover, etc. To use a signal proces-
sor, connect a stereo patch cord from the PRE-OUT jacks
to the processor's line-level input jacks, and a second patch
cord from the processor's output jacks to the amplifier's
MAIN-IN jacks.
NOTE: any signal processor whose operation depends
on the setting of a threshold, such as a dynamic noise filter,
should be connected to the TAPE REC/PLAY jacks-where
the signals are unaffected by the amplifier's volume and tone
controls-rather than the PREAMP OUT 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.
This amplifier can be used as the heart of an elaborate
audiophile sound system. The preamp output is capable of
driving several power amplifiers simultaneously, or of driving
the long signal cables required to connect to power amps
which are located near the speakers (or to "powered" active
loudspeakers with built-in power amplifiers).
11. SOFT CLIPPING. When any amplifier is overdriven
beyond its specified power output it normally produces "hard
clipping" of the signal with harsh distortion and power-supply
buzz as the output transistors saturate. The NAD Soft Clipping
circuit gently limits the output waveform and minimizes audible
distortion when the amplifier is overdriven. If your listening
involves moderate peak power levels, the Soft Clipping may
be left OFF. But we recommend that it be switched ON when
playing music at very high levels that might exceed the
amplifier's power capacity.
12. IMPEDANCE. The impedance of a loudspeaker varies
with frequency, and in many loudspeakers the impedance is
lowest at the frequencies where the highest power demands
occur in music. In the majority of "8 ohm" loudspeakers this
