AUSTRALIAN MONITOR AMIS250P User manual

Clever Features, Contractor Friendly
AMIS250P
250w Power Amplifier
Operating Manual
AMIS250P, 250 Watt Power Amplifier
Product Description
The AMIS250P power amplifier is designed for commercial installations. It can be used for either low
impedance (4 ohm) or 25/70v line speaker systems. It operates on 115 VAC, 60Hz and may be desk or
rack mounted. The AMIS250P features a line level input (with parallel output) and is normally used with
mixers, mixer amplifiers or other power amplifiers. The AMIS250P delivers 250 watts into a load of 4
ohms, 25 or 70 volt line. The AMIS250P also features 24 volt DC operation.

Front Panel Features
Power Switch
The black rocker switch on the right hand side of the front panel is used to switch the amplifier on and off.
The ‘up’ position is on. When the amplifier is connected to an appropriate AC power source and is
switched on, the blue power LED will illuminate. This switch will not switch DC power on or off in DC
operation. In DC operation mode, the amplifier is always on and the blue power LED will always be
illuminated.
On LED
The blue “On” LED above the power switch will illuminate when the amplifier is connected to mains
power and is switched on. In 24vdc operation the LED will always be on.
Signal LED
The green “Signal” LED located next to the ‘On’ LED indicates that the AMIS250P is receiving audio
signal via its line level input. The signal LED is a simple method to trouble-shoot installations especially in
multi amplifier projects. At a glance the signal LED will indicate that audio is reaching the amplifier.
Protect LED
A feature of the AMIS250P is high temperature protection. In most applications, the internal cooling fan
will most probably never switch on. When used with demanding speaker loads or in difficult operating
environments, the fan may regularly switch on to cool the amp down and then switch off again. This
switching on and switching off is quite normal. The “Protect” function is there to protect the amplifier from
a high temperature problems which would only occur if the fan stopped working or became clogged up. In
this very rare occurance, the protect LED will illuminate and the amplifier may shut down. The amplifier
will automatically restart once its internal temperature has fallen within “safe” limits. If the protect LED
illuminates, it is best to switch the amplifier off, let it cool down and then try it again. If the protect LED
illuminates again, please contact the company who supplied or installed the equipment.
Rack Mounting
The AMIS250P is supplied with rack ears attached to allow mounting within a standard 19” equipment
rack. As is the case with almost all audio products, adequate ventilation and air flow is required. When
installing multiple AMIS250P power amplifiers within the one rack, it is recommended that at least one
rack unit of ventilation space is left between every two amplifiers. For table or shelf mounting, the rack
ears can be removed using a screwdriver. Once the rack ears are removed, please reinstall the screws.

Rear Panel Features
AC Power Inlet
The 3 pin IEC power inlet is located on the bottom left of the rear panel and accepts a standard mains
power lead fitted with an IEC connector.
The inlet is equipped with an in-built AC fuse holder fitted with an 8 Amp slow blow fuse plus a spare
fuse.
Please ensure that the mains power cord is disconnected before attempting to check or
replace this fuse. Power consumption is 550VA (max).
24 Volt DC Power Inlet
The AMIS250P feature optional 24VDC power to run off a battery back-up if required. This is connected
via the rear terminal strip. The front panel Power Switch will not switch DC power ‘on’ or ‘off’ in DC
operation. In this mode the amplifier is always ‘on’.
Speaker Output Terminal Strip
Located on the top left of the rear panel is the speaker output terminal strip. Reading from left to right, the
connections are:
COM Common or “-” for low impedance speaker loads (4 ohms).
4The “+” for 4 ohm speaker loads (use with common)
COM Common or “-” for 25v or 70v speaker loads (maximum load of 20 ohms at 70v)
25 The “+” for 25v line speaker loads (use with common)
70The “+” for 70v line speaker loads (use with common)
Please ensure that the correct “Common” is used. Low impedance and 25/70v loads can be used
simultaneously but please pay careful attention to the overall speaker load. When used individually, the low
impedance load should be 4 ohms or higher while the 70v line load should not fall below 20 ohms. When
both outputs are used simultanously, ensure that neither output is loaded to maximum.
Gain Control
Located to the left of the XLR input/output is a recessed screwdriver adjustable gain control. The gain
control is an input attenuation control normally used to match the amplifier to a wide variety of input
signals. In essence, the amplifier is designed to receive a 700mv input signal however the level control can
be used to increase the level for lower signals or decrease the level for higher input signals. In normal use,
the gain control is used as a ‘set and forget’ master level control for the amplifier.
XLR Audio Input and Parallel Output
The AMIS250P includes both male and female 3 pin XLR connectors. While the female is normally used
as the input to the amplifier, both XLR’s are connected in parallel so either will work. When signal is
connected to one XLR, the other XLR becomes a line level output allowing the input signal to be

distributed (split) to other amplifiers. In some projects, the same input may be looped through to multiple
amplifiers using this method. Up to 6 amplifiers can be looped together without any noticeable loss in level.
A distribution amplifier should be used when more than 6 amplifiers need to be looped.
The XLR’s are wired as follows: Pin 1: Shield. Pin 2: Hot, +, Positive. Pin 3: Cold, -, Negative
Fuse Sizes
Mains 115 VAC - 8 Amperes Slow Blow
DC - 2 x 10 Amperes Slow Blow
Notes:
The DC fuse is located on the circuit board. This is a feature of the AMIS series amplifier,
which is equipped with a current limiting circuit preventing excessive DC current, thus
eliminating the risk of blowing high tensions fuses. In the unlikely event that the DC fuse
actuates, the output transistors should be checked, as it is probable that the amplifier has been subjected to
very extreme conditions.
Important Safety Information
1. Save the carton and packing material even if the equipment has arrived in good condition. Should
you ever need to ship the unit, use only the original factory packing.
2. Read all documentation before operating your equipment. Retain all documentation for future
reference.
3. Follow all instructions printed on unit chassis for proper operation.
4. Do not spill water or other liquids into or on the unit, or operate the unit while standing in liquid.
5. Make sure power outlets conform to the power requirements listed on the back of the unit.
6. Do not use the unit if the electrical power cord is frayed or broken. The power supply cords should
be routed so that they are not likely to be walked on or pinched by items placed upon or against them,
paying particular attention to cords and plugs, convenience receptacles, and the point where they exit from
the appliance.
7. Always operate the unit with the AC ground wire connected to the electrical system ground.
Precautions should be taken so that the means of grounding of a piece of equipment is not defeated.
8. Mains voltage must be correct and the same as that printed on the rear of the unit. Damage caused
by connection to improper AC voltage is not covered by any warranty.

9. Have gain controls on amplifiers turned down during power-up to prevent speaker damage if there
are high signal levels at the inputs.
10. Power down & disconnect units from mains voltage before making connections.
11. Never hold a power switch in the “ON” position if it won’t stay there itself!
12. Do not use the unit near stoves, heat registers, radiators, or other heat producing devices.
13. Do not block fan intake or exhaust ports. Do not operate equipment on a surface or in an
environment which may impede the normal flow of air around the unit, such as a bed, rug, weathersheet,
carpet, or completely enclosed rack. If the unit is used in an extremely dusty or smoky environment, the
unit should be periodically “blown free” of foreign matter.
14. Do not remove the cover. Removing the cover will expose you to potentially dangerous voltages.
There are no user serviceable parts inside.
15. Do not drive the inputs with a signal level greater than that required to drive equipment to full
output.
16. Do not connect the inputs / outputs of amplifiers or consoles to any other voltage source, such as a
battery, mains source, or power supply, regardless of whether the amplifier or console is turned on or off.
17. Do not run the output of any amplifier channel back into another channel’s input. Do not
parallel- or series-connect an amplifier output with any other amplifier output.
Australian Monitor Audio Inc is not responsible for damage to loudspeakers for any reason.
18. Do not ground any red (“hot”) terminal. Never connect a “hot” (red) output to ground or to
another “hot” (red) output!
19. Non-use periods. The power cord of equipment should be unplugged from the outlet when left unused
for a long period of time.
20. Service Information Equipment should be serviced by qualified service personnel when:
A. The power supply cord or the plug has been damaged.
B. Objects have fallen, or liquid has been spilled into the equipment
C. The equipment has been exposed to rain
D. The equipment does not appear to operate normally, or exhibits a marked change in performance
E. The equipment has been dropped, or the enclosure damaged.
Engineered in Sydney, Australia
www.australianmonitor.com

Australian Monitor Audio Inc.
PO Box 3126,
Lynnwood,
WA 98046.
Ph: 425 673 5175
Fax: [phone]
E-mail: [email protected]
[e-mail]
[e-mail]
International Sales & Corporate Head Office
Private Bag 149, Silverwater NSW 1811
149 Beaconsfield Street, Silverwater NSW 2128
Australia
Ph: 61-2- 9647 1411
Fax: [phone]
E-mail: [email protected]