NAD 2600 - SPEAKER TERMINALS AND CONNECTIONS; SPEAKER TERMINALS; Phasing; INPUTS AND BRIDGING

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.
5. SPEAKER TERMINALS
The amplifier is equipped with special high-current
binding-post speaker terminals to handle the highest peak
power levels that may occur in the “bridged” mode or with
low-impedance
speakers.
Connect
the
loudspeakers
with
heavy-duty (16-gauge or thicker) stranded wire. Heavy-duty
wiring is especially desirable if you are using speakers of
low impedance or two pairs of speakers wired in parallel.
Each binding post consists of a threaded metal shaft
and a plastic screw-on bushing. Connections may be made
in either of two ways:
(1) A lateral opening in the base of each terminal
accepts bared wires up to 14 gauge in thickness. Separate
the two conductors of the cord, and strip off about a half-inch
(1 cm) of insulation from each. In each conductor, twist
together the exposed wire strands. Unscrew the colored
plastic bushing a few turns, insert the wire into the hole in
the base of the terminal, and screw the bushing down tight
until it grasps the wire and holds it securely.
Connect the wires from the left-channel speaker to
the (L+) and (L—) terminals and the wires from the right-
channel speaker to the (R+) and (R—) terminals.’Check
to be sure that no loose strand of wire is touching any ad-
jacent terminal or the amplifier chassis.
(2) A spring-type banana plug may be inserted axially
into the end of each binding post. The binding posts have the
¥4-inch (19 mm) spacing required to accept standard dual-
banana plugs. Purchase dual-banana plugs and install them
on your speaker cables (or purchase speaker wires with
dual-banana plugs already installed), and plug them into the
binding-post terminals.
If you want to connect two pairs of loudspeakers in
parallel, you may use both methods. Connect your main
speakers permanently via the opening at the base of each
binding post, and use dual-banana plugs for the second pair
of speakers. Then the second pair of speakers can be con-
nected and disconnected easily when desired.
CAUTION: TO AVOID THE RISK OF SHOCK, MAKE
SURE THAT WHEN CONNECTING SPEAKERS THERE
IS NO EXPOSED BARE WIRE WHICH MIGHT BE
CONTACTED.
Phasing. Stereo speakers must operate in phase with
each other in order to yield a good stereo image and to
reinforce rather than cancel each other’s output at low
frequencies. If your speakers are easily moved, their phasing
can easily be checked. Make the connections to both speak-
ers, place the speakers face-to-face only a few inches apart,
play some music, and listen. Then swap the connection of
the two wires at the back of ONE of the speakers, and listen
again. The connection which produces the fullest, boomiest
bass output is the correct one. Connect the wires securely to
the speaker terminals, being careful not to leave any loose
strands of wire that might touch the wrong terminal and
create a partial short-circuit; then move the speakers to their
intended locations.
Ifthe speakers cannot easily be set face-to-face, then
phasing must rely on the “polarity” of the connecting wires.
The speaker terminals on the amplifier are labeled (+)
and (-) in each channel. The terminals at the rear of the
speakers are also marked for polarity, either via red and
black connectors or by labels: “+”, “1”, or “8” ohms for
positive, “-”, “0”, or “G” for negative. As a general rule the
red (+) terminal on the amplifier is to be connected to the
red (positive) terminal of the speaker, in each channel.
To facilitate this, the two conductors comprising the
speaker wire in each channel are different, either in the color
of the wire itself (copper vs. silver) or in the presence of a
small ridge or rib pattern on the insulation of one conductor.
Use this pattern to establish consistent wiring to both speak-
ers of a stereo pair. Thus if you connect the copper colored
wire (or ribbed insulation) to the (+) amplifier terminal in
the Left channel, do the same in the Right channel. At the
other end of the wire, if you connect the copper colored
wire (or the ribbed insulation) to the red or positive terminal
on the left-channel speaker, do the same at the right-
channel speaker.
6. INPUTS (Normal and Lab)
Before making or changing input connections to the
power amplifier, make certain that its Power is switched OFF.
Connect the signal cable from your preamplifier either to
the NORMAL input jacks or to the LAB input jacks.
The NORMAL inputs contain minimum-phase infra-
sonic and ultrasonic filters, whose purpose is to remove
non-musical signals at frequencies below 10 Hz and above
40 kHz (due to turntable rumble, disc warps, radio-frequency
interference, tracing distortion, etc). These inputs should be
used, especially if your preamplifier lacks such filtering.
The LAB inputs bypass these filters, providing extended
response at infrasonic and ultrasonic frequencies.
7. BRIDGING
This switch “bridges” the two power amplifier channels
to
form
a
monophonic
amplifier
with
more
than
double
the
output power. To convert to bridged operation, the following
procedure should be followed.
(1) Switch OFF the POWER.
(2) Be sure that the IMPEDANCE switch is set to 40
(NORMAL). If it is at 8Q (HIGH), re-set it to 4Q (NORMAL).
NOTE: In the bridged mode the loudspeaker’s imped-
ance is effectively halved as “seen” by the amplifier. An
8-ohm load looks like 4 ohms, a 4-ohm load looks like 2
ohms,and pairs of 4-ohm speakers operated in parallel will
look like a 1-ohm load. Driving paralleled low-impedance
speakers to high levels will cause the amplifier to overheat
and shut down, or may cause internal fuses to blow in order
to protect the amplifier. For best results the bridging mode
should be used with a single 8-ohm or higher impedance
speaker in each channel. In either case, the Impedance
switch should be set to 4 ohms.
(3) Disconnect any signal cables from the input jacks.
Decide
whether
this
amplifier
will
be
driving
the
Left
or
Right
speaker. Connect the corresponding (left or right) signal
cable from your preamplifier to one of the L input jacks of
this amplifier (either LAB or NORMAL, as you prefer).
In the bridged mode the amplifier is driven only
through its L (Left) input, and the volume is adjusted with the
Left input control, even though it may be connected to the
“Right” speaker. If another NAD 2600 amplifier in bridged
mode is used for the second stereophonic channel, it also
will be driven through an L input, regardless of whether it is
used to drive the Left or Right loudspeaker.
(4) Disconnect any wires from the SPEAKERS termi-
nals. Select the wire from the speaker that will be driven by
this bridged amplifier. Connect its “positive” conductor to the
L+ terminal and its “negative” conductor to the R+ terminal
(i.e. the two red terminals). DO NOT connect any wires to
the black terminals (L— and R—).
CAUTION: In the bridged mode the speaker wires
must be “floating” with respect to the circuit ground. Do NOT
connect the speaker wires to anything that shares a common
ground between stereo channels (such as some speaker
switches or adapters for electrostatic headphones), nor to any-