Low Impedance Systems; Operation - Adastra DM40 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" (15) output terminal to the positive (+) connection of the speaker and "COM" output (13)
to the negative (-) connection of the speaker. Connect further speakers in parallel to the first speaker
with all positive terminals 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 DM series amplifiers can alternatively provide an output for a single 4-16Ω speaker by
connecting the "4-16Ω" output (14) to the positive (+) speaker connection and "COM" output (13) to
the negative (-) speaker connection. It is important to ensure that the speaker load is no lower than
4Ω 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 (1). Ensure a signal is being fed to the LINE IN connection and gradually increase the AUX
rotary control (8) part way for checking.
Alternatively, connect a microphone to the Mic input (10) and gradually increase the Mic volume (9)
for checking. The microphone should not be able to "hear" the speakers, which can cause feedback
(squealing or howling noise).
The tone character of the output can be adjusted using the TREBLE and BASS controls. The zero
setting for these is halfway (pointing vertically) and turning to the right boosts the BASS or TREBLE
content, whereas turning to the left cuts the BASS or TREBLE content.
Note: If a mic or line input is not connected to the DM series amplifier, the initial test can be made
using the built-in media player. See the information on the following pages for instructions.
DM series mixer-amplifiers User Manual