microphone. While phantom power is not required for the more common Dynamic microphones, it will not
damage them providing that they are balanced. Do not plug an unbalanced microphone in any amplifier or
mixer when phantom power is switched on.
Line Output
The balanced XLR line level output provides a maximum of 700mV to allow for connection to up to 6
power amplifiers. Simply run a balanced cable from the line out of the AMIS250 to the line input of the
power amplifier. Pin connections are:
pin #1
-earth;
pin #2
-signal (high, +);
pin #3
-signal (low, -).
Tape Output
Dual RCA output connectors provide a line level output with a maximum of 350mV into 10K Ohms which
is ideal for a connection to most standard tape recorders. This output is sourced before the master gain
control and as such, the tape output level is not influenced by the operation of the master gain control.
Microphone Inputs
The mic input sensitivity is 1mV @ 200 ohms. Pin connections are:
pin #1
-earth;
pin #2
-signal (high, +);
pin #3
-signal (low, -). Phantom power of +15 volts is available on all microphone inputs. Reading from
left to right across the rear panel, the connection are for microphone inputs 6, 5, 4, 3, 2, & 1 respectively.
Line Inputs
Line inputs 1, 2, 3, 4, & 5 have an input sensitivity of 150mV @ 100K ohms. Input 6 has an input
sensitivity of 300mV @ 220K ohms making it suitable for high level inputs such as a CD player. Reading
from left to right across the rear panel, the connections are for inputs 6, 5, 4, 3, 2, & 1 respectively.
Other Features
Tone Generator
Four separate tones are available from the in-built tone generator board. All four tones can
be activated individually via a contact closure connected to the screw terminals on the rear
of the amplifier. To activate the bell chime for example, just run a pair of wires from the
Tone generator common and the Bell terminal to an external switch. Activating the switch,
or closing the pair of wires, will activate the bell. When any tone is activated, all inputs (except for inputs
one and two) will automatically mute. To adjust the level of the tone generator, disconnect the power lead,
remove the amplifier lid and locate the pot labeled R6. (located behind the Bass adjustment pot). This pot
adjusts the level for all 4 tones.
Tones available on the AMIS250 include:
Evacuation Tone
Alert Tone
Bell Tone
Pre-Announce Chime
Muting
A VOX muting card is installed in the AMIS250. This feature provides automatic muting
of some channels when others are active. It is normally used so that a paging microphone
can have priority (by muting) over background music. VOX muting is available from
channels 1 and 2 meaning that any signal on channels 1 and 2 (mic or line) will mute
channels 3, 4, 5 & 6. The muted channels will automatically ramp back up to normal
volume when the signal on channels 1 and/or 2 is no longer active. The amplifier ships with the VOX
muting function enabled. To disable the VOX muting, disconnect the mains power lead and remove the lid
of the amplifier. Looking down from the front of the amplifier, a three position jumper (labeled JP2) is
