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RMB-1504 Four Channel Power Amplifier
Signal Output Link
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This pair of RCA connections can be used to pass the unprocessed input
signals to another audio component, for example to “daisychain” an additional
amplifier to drive a second set of speakers. The input signals connected to
the “A” channels is also available at these LINK outputs.
NOTE:
These input signals from the “A” channels can also be linked
to the “B” inputs by playing the INPUT SELECT switch associated with
that pair of channels in the LINK position.
Speaker Connection
The RMB-1504 has two groups of speaker connectors, one for each pair
of amplifier channels.
Speaker Selection
We recommend using loudspeakers with a nominal impedance of 4 ohms
or higher with the RMB-1504. You should exercise some caution in driving
multiple pairs of speakers in parallel configuration, because the effective
impedance 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, it is recommended that you 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 RMB-1504. See your authorized Rotel dealer if you have
any questions.
Speaker Wire Selection
Use insulated two-conductor stranded wire to connect the amplifier to the
speakers. The size and quality of the wire can have an audible effect on the
performance of the system. 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 cables for your system.
Polarity and Phasing
The polarity, the positive/negative orientation 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 reversed, 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 insulation with different color
conductors (copper and silver). There may be polarity indications printed
on the insulation. Identify the positive and negative conductors and be
consistent with every speaker and amplifier connection.
Speaker Connections
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See Figure 2
NOTE:
The following text describes both binding post and plug-in
connections. DO NOT use both connection methods in combination to
connect multiple speakers.
Turn off all the components in the system before connecting the speakers.
The RMB-1504 have two color coded connections for each group of
amplifier channels, one for the left speaker, the other for the right speaker.
Labels above the connectors show the proper connections for connecting
speakers. These speaker connectors accept bare wire, connector lugs, or
PROTECTION LEDS for each pair of channels which may help in
troubleshooting the cause of the problem. When you turn the amplifier
back on, the protection circuit will automatically reset and the PROTECTION
LEDS should go out, indicating that the amplifier has recovered and the
fault corrected.
In most cases, the protection circuitry activates because of a fault condition
such as shorted speaker wires, or inadequate ventilation leading to an
overheating condition. In very rare cases, highly reactive or extremely low
impedance speaker loads could cause the protection circuit to engage.
If the protection circuitry triggers repeatedly and you are unable to isolate
and correct the faulty condition, contact your authorized Rotel dealer for
assistance in troubleshooting.
Signal Connections
The RMB-1504 has conventional RCA type input connectors, the type found
on nearly all audio equipment.
There is also a pair of SIGNAL OUTPUT LINK connections for passing the
input signal connected to the “A” pair of channels on to another audio
component. Additionally, the input signal to the “A” pair of channels can
be automatically linked to the inputs for the “B” channels, so that a separate
input signal cable is not required for those channels, for example in large
systems where the RMB-1504 is being used to drive multiple pairs of speakers.
NOTE:
To prevent loud potentially damaging noises, make sure the amplifier
is turned off when you make any changes to the input signal configuration.
RCA Inputs
4
See Figure 2
There is one RCA input for each of the two pair of amplifier channels. These
RCA inputs accept audio signals from preamplifiers or surround sound
processors. Use high quality audio interconnect cables for best performance.
For each pair of amplifier channels, connect the left channel output of your
preamp to the LEFT INPUT on the RMB-1504. Connect the right channel of
your preamp to the RIGHT INPUT. Make sure that the input slide switch to
the right of the RCA inputs is in the STEREO position.
Mono Switch
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When the MONO switch is in the ON position, the “A” left channel input
is connected to the right channel.
Linking the Inputs
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You can link the inputs for groups “B” to the “A” inputs by placing the input
slide switch to the right of the “B” pair of RCA inputs in the LINK position.
When linked, no input connection is required for that group. The input
signal from the “A” group is sent to the linked pair of channels, allowing
you to use all four amplifier channels with the same stereo input signals.
Input Level Controls
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Two controls on the front panel, one for each pair of channels, provide
input level adjustments. These allow you to adjust the gain of the amplifier
to match other components in the system. The A level control changes the
gain of the “A” channels; the B level control changes the “B” channels.
To adjust these controls, use a small, flat blade screwdriver. Turn the control
clockwise to increase gain. Turn counterclockwise to reduce gain.
