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8
Input Signal Connections
The RB-1090 gives you a choice of two dif-
ferent kinds of input connections — conven-
tional unbalanced RCA type connections
(such as found on nearly all audio equip-
ment) or balanced XLR-type connections for
use with some high-end preamps or digital
processors featuring this lower noise con-
nection.
Input Selector Switch
A toggle switch in the middle of the RB-1090’s
rear panel selects which type of input sig-
nal to use. The operation of this switch is
self-evident. Put the switch in the
unbalanced
position when you are using the RCA-type
inputs. Put the switch in the
balanced
posi-
tion when using XLR-type connections.
NOTE
: To prevent loud potentially damag-
ing noises, make sure the amplifier is
turned off when you make any signal con-
nections.
RCA Inputs (unbalanced)
See Figure 2
When a component with RCA connectors
– such as a preamplifier or surround sound
processor – supplies signals to the RB-1090,
the RCA-type phono plug inputs should be
used.
Select high quality audio interconnect cables.
Connect the left channel output of your
preamp to the left channel
UNBALANCED IN-
PUT on the RB-1090. Connect the other cable
to the right channel
UNBALANCED INPUT. Make
sure that the input selector switch is in the
UNBALANCED position.
XLR Inputs (balanced)
See Figure 3
If you are using one of the high-end pream-
plifiers or processors with low-noise balanced
signal outputs to drive your RB-1090, you
may choose to use these low-noise XLR-type
connections. See your authorized Rotel dealer
for the appropriate cables.
Connect the left channel output of your
preamp to the left channel
BALANCED INPUT
on the RB-1090. When properly seated, the
connector should click into the connection.
Connect the other cable to the right chan-
nel
BALANCED INPUT. Make sure that the IN-
PUT SELECTOR SWITCH is in the
balanced
posi-
tion.
Speakers
The RB-1090 has two sets of SPEAKER CON-
NECTORS for each channel. These can be used
to connect two pairs of loudspeakers, or to
connect one pair of loudspeakers with bi-
wire connections.
Speaker Selection
The nominal impedance of the loudspeaker(s)
connected to the RB-1090 should be at least
4 ohms. When driving multiple pairs of speak-
ers in parallel configuration, the effective im-
pedance the amplifier sees is cut in half. For
example, when driving two pair of 8 ohm
speakers, the amplifier sees a 4 ohm load.
When driving multiple speakers in parallel,
select speakers with a nominal impedance
of 8 ohms or higher. Speaker impedance
ratings are less than precise. In practice, very
few loudspeakers will present any problems
for the RB-1090. See your authorized Rotel
dealer if you have any questions.
Speaker Wire Selection
Use insulated two-conductor stranded wire
to connect the RB-1090 to the speakers. The
size and quality of the wire can have an au-
dible effect on the performance of the sys-
tem. Standard speaker wire will work, but
can result in lower output or diminished bass
response, particularly over longer distances.
In general, heavier wire will improve the
sound. For best performance, you may want
to consider special high-quality speaker
cables. Your authorized Rotel dealer can help
in the selection of appropriate cables for your
system.
Polarity and Phasing
The polarity – the positive/negative orien-
tation of the connections – for every speaker
and amplifier connection must be consistent
so all the speakers will be in phase. If the
polarity of one connection is mistakenly re-
versed, bass output will be very weak and
stereo imaging degraded. All wire is marked
so you can identify the two conductors. There
may be ribs or a stripe on the insulation of
one conductor. The wire may have clear in-
sulation with different color conductors (cop-
per and silver). There may be polarity indi-
cations printed on the insulation. Identify the
positive and negative conductors and be con-
sistent with every speaker and amplifier con-
nection.
Connecting the Speakers
See Figure 2
The RB-1090 has two pairs of color coded
binding posts per channel. These can be used
to connect two pairs of loudspeakers by con-
necting one pair to the first speaker and the
second pair to the other speaker. Alterna-
tively, they may be used for bi-wire connec-
tions by connecting one pair to the high-fre-
quency input on the speaker and the other
pair to the low-frequency speaker input.
These
SPEAKER CONNECTORS accept bare wire,
connector lugs, or dual banana type con-
nectors (except in the European Community
countries where their use is not permitted).
Route the wire from the RB-1090 to the speak-
ers. Give yourself enough slack so you can
move the components enough to allow ac-
cess to the
SPEAKER CONNECTORS.
If you are using dual banana plugs, connect
them to the wires and then plug into the backs
of the
SPEAKER CONNECTORS. The collars of the
SPEAKER CONNECTORS should be screwed in
all the way (clockwise).
If you are using terminal lugs, connect them
to the wires. If you are attaching bare wires
directly to the
SPEAKER CONNECTORS, separate
the wire conductors and strip back the in-
sulation from the end of each conductor. Be
careful not to cut into the wire strands. Un-
screw (turn counterclockwise) the
SPEAKER
CONNECTOR collars. Place the connector lug
around the shaft, or insert the bundled wire
into the hole in the shaft. Turn the collars clock-
wise to clamp the connector lug or wire firmly
in place.
NOTE
: Be sure there are no loose wire
strands that could touch adjacent wires or
connectors.
RB-1090 Stereo Power Amplifier