Low Impedance Systems; Operation - Adastra RMC120 SERIES User Manual

100V line systems
For 100V line systems, connect the amplifier to the first speaker in the system using double-insulated speaker
wire which has adequate current rating to handle the total output of the amplifier.
Connect the "100V" output terminal to the positive (+) connection of the speaker and "COM" output to the
negative (-) connection of the speaker. Connect further speakers in parallel to the first speaker with all
positive terminals and connected together and all negative terminals connected together as shown below.
A 100V line speaker system can comprise of many speakers connected together. The determining factor for
how many speakers can be used on a single amplifier is the power rating. For most purposes, it is advised to
connect as many speakers as needed with a combined wattage of no more than 90% of the amplifier's output
power rating.
The terminals of a 100V speaker are connected to a transformer and in some cases, this transformer may be
"tapped" for different power ratings. These tappings can be used to adjust the wattage (and output volume)
of each speaker in the system to help achieve the ideal total power of the system for the amplifier.

Low impedance systems

The RMC120 can provide an output for a single 8Ω speaker by connecting the "8Ω" output to the positive (+)
speaker connection and "COM" output to the negative (-) speaker connection. It is important to ensure that
the speaker load is no less than 8Ω and that the power handling of the speaker is equal to or greater than the
output power of the amplifier.

Operation

When all connections to the amplifier are made, turn all rotary controls down and switch on the power (14)
and a power "ON" LED will illuminate. Turn BASS and TREBLE controls (11, 12) to the 12 o'clock position
(pointing straight up) and turn MASTER rotary control (13) up part way for testing.
Ensure a signal is being fed to one of the line inputs 2, 3, 4 or 5 and gradually increase the volume control for
that channel until the output is heard through the speakers. Turn up the MASTER to the maximum required
volume level and reduce the channel volume control if necessary. Repeat this process for any other line inputs
connected to channels 2, 3, 4 or 5.
Note: The initial test can be made using the built-in CD/USB/SD/FM audio player. See section below for
instructions. Both the audio player output and LINE 5 input are governed by the LN5/CD volume control (10)
The output of the amplifier is represented on the level meter LEDs (15) and care should be taken that the Red
"0" LED is only lit momentarily during use. Anything longer than a short flash of this LED may be indicating
distortion or clipping of the output signal and the MASTER should be turned down.
If a microphone is connected to MIC 1 input, make sure it is switched on and if it requires phantom power,
make sure this feature is enabled. Gradually increase the MIC 1 control (6) whilst speaking into the
microphone until the required volume level is reached. The microphone should not be able to "hear" the
speakers, which can cause feedback (squealing or howling noise). Repeat this process for microphones
connected via the MIC/LINE 2 and MIC/LINE 3 inputs.
953.141UK User Manual