located just to the left and behind the level pot for channel 1. To disable VOX muting, move the jumper to
the middle and left pins.
(The factory setting is with VOX enabled with the jumper on the middle and right pins).
600 Ohm Telephone Input
The 600 ohm transformer balanced Telephone Input is paralleled with input 2. If telephone paging is
required the XLR & dual RCA inputs should not be used as these inputs will be summed with the
Telephone Input into channel 2. The front panel level control will set the gain for the Telephone Input.
Insert Point
The AMIS250 includes an Insert Point to allow for connection of signal processors such as equalisers,
compressors or Feedback Exterminators. The Insert Point is located (electronically) between the mixer and
power amplifier sections of the AMIS250. It allows for the “mixed” output of the AMIS250 to be
processed externally and then returned to the power amplifier section of the AMIS250.
The Insert Point is a 3 conductor (Tip, Ring, Sleeve) socket which accepts a standard stereo 6.35mm (1/4”)
jack. The one jack allows for signals to be “sent” to the processor and then “returned” to the power
amplifier. The connections are:
Tip
Amplifier in. This is the return signal from the processor
Ring
Mix Output. This is the signal from the mixer stage which is to be sent to the processor
Sleeve
This is the ground connection
When an external processor is used via the insert point, it only affects the power amplifier section of the
AMIS250. The tape output remains unprocessed.
VCA Control
An external pot (500K) can be connected to the AMIS250 for remote control of the master level. The
external pot is governed by the master level of the amplifier allowing the installer to set the volume, then
lock the amplifier in a rack, leaving the user with just a master volume control that cannot go beyond the
level set on the master (front panel) control. Connection is via a 2 wire terminal strip on the rear panel of
the amplifier.
VOX Relay Output
The terminal strip to the immediate right of the AC inlet features a relay output. This relay
is activated when signal is present on any of the priority inputs. This would normally be
inputs 1, 2 and 3 however some or all of these channels can be removed from the priority
bus via internal links (see “Muting” earlier on in this manual). The unit is shipped from the
factory with inputs 1, 2 and 3 having priority so assuming that this has not been changed,
then signal from any of these inputs will activate the VOX relay circuit.
The relay outputs are C (Common), NO (Normally Open) and NC (Normally Closed). The NO or NC
selection provides the installer with the option of the relay either opening or closing a contact. This feature
is normally used in conjunction with relay override attenuators (volume controls). In this application, the
relay output could trigger an accessory power supply which in turn bypasses the remote attenuators. The
result is that priority inputs will always be heard irrespective of the attenuator setting. The relay contacts
are 3 amps at 125VAC/30VDC
Fuse Sizes
Mains, 115 VAC: 8 Amperes Slow Blow
DC: 10 Amperes Slow Blow