Speaker Outputs; Low Impedance Systems - Adastra V-122 User Manual

It is important to match the input level of the source, whether MIC or LINE level using the DIP switches
(19) as shown opposite.
The switch next to MIC/LINE selection enables PHANTOM 20V power to the XLR and screw terminals.
Note: If PHANTOM power is switched ON, use only balanced wiring to the input (not unbalanced).
MIC LINE inputs 1, 2, 3 each have a volume control above the relative front 6.3mm jack inputs (3, 4, 5)
Also on the rear panel are 2 LINE INPUTs A and B (17) which can be connected via RCA connectors and
have individual LEVEL trim controls (18) to adjust the input level of each.
Another RCA input is the AUX IN (16) which is parallel with the 3.5mm AUX input on the front panel (2)
This input has its own AUX level control directly above the front 3.5mm jack.
For DAB/DAB+/FM radio reception, it is advised to connect a suitable antenna (or aerial) to the rear panel F-
type connector (24). Without this, radio reception will be very limited.
If a standard 24V trigger from an emergency panel is available, this may be connected to the 24V MUTE
contacts on the rear panel (23) which will mute output of all channels except for MIC/LINE 1 in an emergency.

Speaker outputs

V-series amplifiers can be used either as 100V line amplifiers or standard low impedance power amplifiers.
These 2 cannot be used together, so it is important to decide which method will be used at the start.
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 multiple speakers wired in parallel. 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 up to 90% of the amplifier's maximum output.
The terminals of a 100V speaker are connected via a small 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

Alternatively, each zone output of a V-series amplifier is capable of powering one or more low impedance
speakers. The benefit this offers is to improve the sound quality using less expensive speakers.
(100V speakers include the added cost of a transformer, which also effects the frequency response)
953.251UK, 953.252UK User Manual