Martin Audio MA900 - SCHEMATICS User manual

Martin Audio – MA900 Amplifier
ENGLISH
1
CONTENTS (ENGLISH) Page No
1CONTENTS MA900 USER GUIDE 1
2APPROVALS 2
3WARNINGS 2
3.1 EXPLANATION OF GRAPHICAL SYMBOLS 2
3.2 WARNING 2
3.3 CAUTION 2
3.4 IMPORTANT SAFETY INSTRUCTIONS 2
3.5 USER RESPONSIBILITY 3
3.5.1 LOUDSPEAKER DAMAGE 3
3.5.2 SPEAKER OUTPUT HAZARD 3
3.5.3 RADIO INTERFERENCE 3
4INTRODUCTION 4
4.1 UNPACKING 4
4.2 FRONT PANEL 4
4.3 REAR PANEL 5
5REAR PANEL FEATURES 5
5.1 GAIN SWITCH 5
5.1.1 THE DIP-SWITCH 6
5.1.2 SENSITIVITY 6
5.1.3 OPTIONS 6
5.2 LINK SWITCH 6
5.3 OPERATING MODES 6
5.3.1 STEREO MODE 6
5.3.2 NOTES FOR AMPLIFIER TESTING 7
5.3.3 TANDEM MODE 7
5.3.4 BRIDGE MONO MODE 7
5.3.5 BRIDGE MONO MODE FEATURES 7
6INSTALLATION 8
6.1 MOUNTING 8
6.2 COOLING 8
6.3 OPERATING VOLTAGE 8
6.4 GROUNDING 9
6.5 POWER CONSUMPTION 9
6.5.1 CALCULATION 9
7CONNECTIONS 10
7.1 INPUT CONNECTIONS 10
7.1.1 BALANCED INPUTS 10
7.1.2 UNBALANCED INPUTS 11
7.2 CONNECTING SPEAKERS 11
8OPERATION 12
8.1 OPERATING PRECAUTIONS 12
8.2 POWERING UP – SOFT START 12
8.3 INPUT ATTENUATORS 12
8.4 INDICATORS 12
9PROTECTION FEATURES 12
9.1 OUTPUT LIMITER 13
9.2 VHF PROTECTION 13
9.3 SHORT CIRCUIT PROTECTION 13
9.4 AC MAINS VOLTAGE PROTECTION 13
9.5 DC PROTECTION 13
10 MAINTENANCE 13
10.1 TROUBLESHOOTING 14
11 WARRANTY 15
12 SPECIFICATIONS MA900 16
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Martin Audio – MA900 Amplifier
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2APPROVALS
This equipment conforms to the requirements of the EMC directive 89/336/EEC, amended by
92/31/EEC and 93/68/EEC and the requirements of the Low Voltage Directive 73/23/EEC, amended
by 93/68/EEC.
Standard Applied EMC Emission EN55103-1, E3
EMC Immunity EN55103-2, E3, with S/N below 1% at normal operation level.
Electrical Safety EN60065, Class
3WARNINGS
3.1 Explanation of graphical symbols
The lightning symbol within a triangle is
intended to alert the user to the presence of
lethal voltages within the amplifier that are of
sufficient magnitude to constitute a risk of electric
shock to humans.
The exclamation mark within a triangle is
intended to alert the user to the presence of
important operating and service instructions in the
literature accompanying the product.
3.2 WARNING
To reduce risk of fire or electric shock, do not expose
this apparatus to rain or moisture.
3.3 CAUTION
To reduce the risk of fire or electric shock, do not
remove screws. There are no user-serviceable parts
inside this amplifier. Refer servicing to qualified
personnel only.
3.4 Important Safety Instructions
Before using your amplifier, please read the operating instructions and the safety suggestions.
1. Keep this manual for future reference.
2. Do not operate the amplifier if liquid ingress is suspected.
3. Do not stand water or any other liquid on, or near the amplifier.
4. Do not use this amplifier near water. Do not operate the amplifier if wet or standing in liquid.
5. Clean only with dry cloth.
6. Do not block the air intake or exhaust ports. Always install the unit in accordance with the instructions.
7. Do not operate the amplifier on or near any source of heat, such as radiators, lighting dimmer racks, or
other apparatus that produce heat.
8. Always operate the unit with the chassis ground wire connected to the electrical safety earth. Do not
tamper with the electrical safety earth, it is provided for your safety. A grounding type plug is fitted; this
has two pins and a third grounding prong. If the plug provided does not fit your mains outlet, consult an
electrician or a competent person to replace the fitted plug. See page 9 section 6.3 for wiring colour code
9. Connect only to AC power outlets rated 230 - 240V (or 100 - 120 V), 50-60Hz.
10. Do not use this amplifier if the mains cable is damaged or frayed, particularly check where the mains
cable exits the amplifier and the mains plug. Protect the mains cable from being walked upon or rolled
over by heavy objects.
11. Only use accessories specified by the manufacturer.
12. The unit is intended to use in a 19î rack. Follow the mounting instructions. When racks with wheels are
used, use caution to avoid injury from tipping when in motion.
!
!
!
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Martin Audio – MA900 Amplifier
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13. Unplug this apparatus during lightning storms or when unused for long periods of time.
14. Do not connect an amplifier output in parallel or series with any other amplifier’s output. Do not connect
the amplifier output to any other voltage source, such as a battery, mains outlet, or power supply,
regardless of whether the amplifier is turned on or off.
15. Do not run the output of any amplifier back into another channel's input.
16. Refer all servicing to qualified personnel only. Servicing is required when the apparatus has been
damaged in any way such as:
•Mains cable, or plug is damaged
•Liquid has entered the amplifier.
•An object has fallen into the unit
•The amplifier has been exposed to rain or moisture
•The amplifier does not operate normally
•The amplifier was dropped or the enclosure is damaged
17. Do not remove top or bottom covers. There are no user serviceable parts inside the amplifier, removal of
the covers will expose hazardous voltages, and may void the warranty.
18. An experienced person should always supervise inexperienced adults or minors when using professional
audio equipment
3.5 User responsibility
3.5.1 Loudspeaker damage
Your amplifier is very powerful and can be potentially dangerous to both loudspeakers and humans alike.
Many loudspeakers can be easily damaged or destroyed by overpowering, especially with the high power
available from a bridged amplifier. Always check the speaker’s continuous and peak power capabilities.
Even when using the amplifier’s front panel attenuator's to reduce the gain, it is still possible to reach full output
power, if the input signal level is high enough.
3.5.2 Speaker output hazard
Power amplifiers are capable of producing hazardous output voltages. To avoid the risk of electric shock, do
not touch any exposed loudspeaker wiring, when the amplifier is operating. See page 10 Connecting
loudspeakers.
3.5.3 Radio interference
A sample of this product has been tested and complies with the limits for the European Electro Magnetic
Compatibility (EMC) directive. These limits are designed to provide reasonable protection against harmful
interference from electrical equipment. This product uses radio frequency energy and if not used or installed in
accordance with these operating instructions, may cause interference to other equipment, such as radio receivers.
Compliance with the (EMC) directive does not automatically guarantee non- disturbance of susceptible equipment
in close proximity to this amplifier.
If this equipment is suspected of causing interference this can be easily checked by powering the amplifier on and
off and observing the disturbance. The user can correct the interference by one or more of the following measures:
•Re - orientate or relocate the antenna.
•Increase the distance between the amplifier and the effected equipment
•Connect the mains cable to a socket on a different circuit from that to which the affected equipment is
connected.
•Check if the affected equipment complies with the EMC limits for immunity, (CE-labelled). If not,
address the problem with the manufacturer or supplier. All electrical products sold in the EC must be
approved for immunity against electromagnetic fields, high voltage flashes, and radio interference.
•Consult your dealer or an experienced engineer/ technician for help.
All material © 2007. Martin Audio Ltd. Subject to change without notice.

Martin Audio – MA900 Amplifier
ENGLISH
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4INTRODUCTION
Thank you for purchasing a Martin Audio power amplifier. This manual contains important information on operating
your amplifier correctly and safely. Please take some time and read this manual and familiarize yourself with the
advanced features of this amplifier.
4.1 Unpacking
Each Martin Audio MA series amplifier is built to the highest standard and thoroughly inspected before it leaves the
factory. After unpacking the unit, examine it carefully for any signs of transit damage and inform your dealer if such
damage is found. It is suggested that you retain the original packaging so that the unit can be repackaged at a
future date if necessary.
Please note that Martin Audio and its distributors cannot accept responsibility for damage to any returned product
through the use of non - approved packaging.
4.2 Front panel
PROTECT
CLIP
-4 0dB
ON
MA9 0 0
0
1
832 45 7 6
11
1. Input level attenuators
These controls are used to set the signal level entering the amplifier. They are calibrated in dB's to assist the setup of
active loudspeaker systems. (See page 12).
2. Protect indicator
This indicator illuminates if the amplifier attempts to function above its maximum operating temperature (90°°C).
The indicator first comes on as a warning, to either turn down the input level or check the cooling arrangements,
after which point the amplifier will mute the input signal. When the cooling fans have returned the output heat sinks
to the normal operating temperature the input signal is un-muted.
The protect LED also illuminates when constant signals above 12 kHz at full power are detected at the output
terminals or if the short circuit protection is activated. If this occurs the input signal is muted, and the process repeats
until the VHF signal is no longer present or the short circuit is removed. (See page 13).
3. Clip/limit indicator
This indicator signals when the amplifier output is clipping or limiting. It has two different indication states:
When the clip limiter is engaged, it has a short time constant and it illuminates briefly. (See page 13).
4. Signal present indicator.
This LED Illuminates at –40dB below full output signal.
5. On indicator
The two bottom green ”ON” LED's indicate that the output circuits are receiving the correct rail voltage.
6. Power switch
Turns the mains power “ON” or “OFF”.
(See page 8and11)
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Martin Audio – MA900 Amplifier
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7. Fan grille filters
A grille with foam filters is located on the front panel to prevent dust from entering the amplifier. The grille is removable
for easy cleaning of the filter by simply pulling them off. The foam filter should always be used.
8. Carry/protection handle
Both handles can be used to carry the amplifier; they also act as protection for the front panel. In fixed installations
or where rack front covers are too shallow, they may be removed by unscrewing the retaining bolts behind the front
panel.
4.3 Rear Panel
230-240V 50-60Hz
Cu rrent consumption: 5. 5A
STEREO
On
fOf
13 45678 5 4 1
93
678
123
+ -
Gnd
CH.B INPUT
Made in th e EEC by
MARTIN AUDIO MA 90 0
OUTPUT CH.B CH. B INPUT
XLR
Pi n 1 Sc rn Sl e e v e
2 Pos Tip
3 Neg Ring
1/4"
Ser. No:
OUTPUT CH.A
Must be grounded
Clip Li mi ter A
1 + CH.B +
1 - CH.B-
Clip Lim i ter B
On
Off
GA IN
41dB
38dB
35dB
32dB
29dB
26dB
23dB
20dB
+ -Gnd
CH. A INPUT
CH.A IN PUTGAI N
CH.B
GAI N
CH . A
LINK/BRIDGE A +B
ON
OFF
STEREO
1+ CH.A+
1- CH.A-
2+ CH.B+
2- CH.B-
BRIDGE
Pi n 1+ S p k +
2 - Spk-
1. Output / Speaker connector
The Neutrik Speakon connector is used on the outputs of the amplifier. A full description is found in the operation
section. (See page 11).
3. Clip limiter switch
Turns the clip limiter “ON” (switch IN position) or “OFF” (switch OUT position). (See page 13).
4. Input signal XLR.
The Neutrik Combo jack is used which also features a _” TRS phone jacks. (Pin 2 is “hot”, see page 10).
5. Link / Input. A 'Phoenix' screw terminal connector, connected in parallel to the female XLR input is provided for
hard wiring the input, or linking to another input.
6. Gain switch channel B. Three of the switches in the DIP-switch (1,2,3) select the gain of the channel to be either
20, 23, 26, 29, 32, 36, 39 or 41 dB. (See page 5).
7. Link and Polarity reverse switch. The two middle switches in the DIP-switch are used for Link and / or Bridge
operation. (See page 6).
8. Gain switch channel A. Three of the switches in the DIP-switch (6,7,8) select the gain of the channel to be either
20, 23, 26, 29, 32, 36, 39 or 41 dB. (See page 5).
9. AC Mains cable. WARNING!
A label just below the mains cable on the rear of the amplifier indicates the selected AC mains operating
voltage. Connect the mains cable only to the AC source referred to on the label.
5REAR PANEL FEATURES
5.1 Gain switch
The gain switch located on the rear panel (the central DIP-switch) changes the input sensitivity of the amplifier. This
can be useful when using low or high nominal input signals. Most professional mixing consoles operate at a level of
+4 to +6 dBu; therefore the 32dB-gain position ensures there is plenty of fader movement availabl e . F o r a s e m i
professional mixing desk operating at a nominal level of 0dBu or -10dB the higher gain settings of the amplifier can be
used.
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Martin Audio – MA900 Amplifier
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5.1.1 The DIP-switch
Different gains and function can be selected for channel A and B, by
appropriate setting of the DIP switch. Selecting the maximum gain of the
amplifier is always a trade off between noise and headroom. A low gain
amplifier amplifies less of the noise of the preceding equipment (mixer,
crossover, equalizer etc.). A higher input level is then required to attain full
power output, so the headroom will be decreased on mixer or crossover
outputs. In an actively driven system there is usually a dedicated loudspeaker
processor or controller, for the loudspeaker system. Some loudspeaker
manufacturers recommend a specific gain for the amplifiers for use with their
controllers.
There are eight positions of gain, selectable from 20dB, to 41dB in 3dB steps.
The different settings for the DIP-switches are listed in the table below. The three switches to the very left are for
channel B, and the three to the very right are for channel A. The two switches in the middle select the operating mode
of the amplifier, Stereo or Link /Bridge A+B.
5.1.2 Sensitivity
Sensitivity is the input level in volts (rms.) or dBu (referred to 0.775Vrms) that is
required to obtain full output power. As the output power varies with the load
impedance, 4 ohms is usually taken as the reference. The table below gives input
volts rms Versus gain for full output power @ 1% t.h.d, 1Khz sinewave 4 Ohm load.
5.1.3 Options
As the DIP-switch is recessed, A security sticker can be placed across the bay to prevent unauthorized tampering
once the gain has been set. Another option is to remove the DIP-switch. This should only be carried out by qualified
service personnel! This corresponds to all switches set to “OFF”, i.e. 32dB gain and stereo mode.
5.2 Link switch
The Link switch located on the rear panel (the central DIP-switch) is for changing the operating mode of the amplifier
( section 5.3).
5.3 Operating modes
5.3.1 Stereo mode
In this configuration, both channels operate independently of each other. This is used
for all 2-channel operations, eg Bi amp and stereo. Stereo mode is selected by
placing the two central switches in the “OFF” position (Down). The attenuators on the
front panel control the respective channel levels.
Never connect either output terminal to ground or in parallel. The recommended
minimum nominal impedance, for stereo or tandem operation, is 2 ohms per channel.
Gain dB 20 23 26 29 32 35 38 41
Input dBu +13.3 +10.3 +7.3 +4.7 + 1.7 -1.3 - 4.3 - 7.3
Input V rms 3.58 2.53 1.79 1.27 0.90 0.64 0.45 0.33
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5.3.2 Notes for amplifier testing
NOTE: Channel B is always polarity reversed on the input, and polarity reversed back on the output. On
channel B the positive output voltage with respect to 0V appears on pin -2 of the Speakon connector.
Channel A is connected with normal polarity. By having channel A and B operating in opposite polarity,
the energy storage in the power supply is more efficient. This is significant for signals below 100 Hz (sub bass etc.)
and improves the power bandwidth. Be sure to use balanced inputs on all measuring equipment (including
oscilloscope probes) if you are bench testing.
Reverse operation of Channel B.
5.3.3 Tandem mode
In tandem mode channel A input is linked to channel B input, either input socket may then be used to provide the
input signal. Tandem mode is activated by placing the two central switches (4 and 5) in the "ON" position (UP).
Both input attenuators' are active, allowing you to set different levels for each channel. Note that only the inputs are
connected in parallel. This is NOT a parallel output mode. Never connect either output terminal to ground or in
parallel.
You can use the remaining input connectors to parallel off “Daisy – chain” signals to other amplifiers.
NOTE: Always turn off the Link switches when using the amplifier for Bi-amping.
5.3.4 Bridge mono mode
Bridge mono mode is used to deliver increased power to the loudspeakers. Using
the MA900 in bridge mode reduces the number of output channels from two to one.
The nominal impedance of the load must be more than 3 ohms. Set the Link/Bridge
A+B switches to "ON" (UP) and use either of the input connectors A or B. You can
use the remaining input connector to carry a parallel signal to other amps. Both A
and B level attenuators must be at the same position. We recommend they are
used in the 0dB fully clockwise position. The loudspeaker should now be connected
to Channel A output Speakon. (+1 should be connected to the [+] positive terminal
of the loudspeaker, and -2 to the [-] negative terminal of the loudspeaker.
5.3.5 Bridge mono mode features
Bridged mono mode combines the power of two output channels into one. This results in twice the voltage swing,
four times the peak power and just less than three times the full power of a single channel.
This is because the coil is driven with positive voltage at one pole and an equivalent negative voltage at the other
pole. So, if an 8 ohms load is connected in bridged mode, one channel shares one 4 ohms part of the load, and the
other channel shares the other 4 ohms part. The power into 4 ohms from an MA 900 is 700W. So, the total bridged
power into the 8 ohms load will be 2 x 700 = 1400W
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Martin Audio – MA900 Amplifier
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6INSTALLATION
6.1 Mounting
The amplifier is two rack unit's high (2U) and weighs 15Kg (33lbs) and will mount in a standard EIA 19” rack.
Amplifiers may be stacked directly on top of each other. There is no need for spacing between units. If it is the
intention to fill a rack with amplifiers, we recommend racking is started from the bottom of the rack. It is also
recommended that rear supports are used for amplifiers mounted in the middle of the rack, especially if used as
part of a portable system.
6.2 Cooling
Your amplifier uses a forced air cooling system to maintain a low and even operating temperature. All fan cooled
MARTIN AUDIO MA Series amplifiers have front to rear cooling. Never try to reverse the airflow, as the amplifier
needs a pressure chamber between the fans and heat sink, and this only operates in one direction of the airflow.
Make sure that there is an adequate air supply in front of the amplifier, and that the rear of the amplifier has
sufficient space to allow the exhaust to escape. If the amplifier is rack-mounted, do not use covers or doors on the
front or rear of the rack. Should a heat sink get too hot, its sensing circuit will mute the hot channel. If the power
supply overheats, another sensing circuit will mute all output channels, until it cools down to a safe operating
temperature.
For installations with a central cooling system, usually found in fixed installations with a dedicated rack room, it may
be necessary to calculate the maximum heat emission. Refer to Power consumption on page 9. Remember! Never
rack different makes of amplifiers together that have opposing air flow characteristics.
6.3 Operating voltage
WARNING!
A label just below the mains cable on the rear of the amplifier indicates the selected AC mains operating voltage.
Connect the mains cable only to the AC source referred to on the label. The warranty will not cover damage
caused by connecting to the wrong type of AC mains.
If the power plug is not appropriate for your country, it can be cut off and re- wired to a suitable connector in the
following way:
BLACK or BROWN LIVE
WHITE or BLUE NEUTRAL
GREEN or GREEN/YELLOW EARTH
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Once connected to a suitable AC supply, the amplifier can be started with the power switch. When you power up the
amplifier it takes a couple of seconds to self check (this is known as the "soft start" or "slow start" sequence), the fans
then blow at high speed before going into "idle". The two bottom green LED’s then illuminate to show the amplifier is
operational.
6.4 Grounding
There is no ground lift switch on this amplifier. The signal ground is always floating (lifted), with respect to chassis
ground via a ground lift resistor. If a potential difference above 0.6V is detected between signal ground and chassis
earth, a short circuit is automatically introduced between the two, ensuring electrical protection. If other equipment or
amplifiers within a system should develop an electrical fault to earth, the mains fuse on that equipment should rupture
due to this automatic system allowing an earth fault current to flow for protection purposes.
If however you wish to permanently connect the signal ground to chassis earth, connect the XLR-connector’s shell lug
to pin 1. In the interest of safety never disconnect the earth pin on the mains cable.
To comply with CE approval (radio interference), there is an AC mains filter. This filter needs the chassis earth for
reference, otherwise a current loop is formed via the signal ground.
Never disconnect (lift) the mains safety earth.
6.5 Power consumption
There are three ways to determine the power/current consumption of the amplifier:
First, the peak current draw at full power output. Under this condition the amplifier will operate for less than 2
minutes before thermally limiting or blowing the mains fuse.
Second, the maximum expected average current under worst case program material, which is 1/3 of full power
according to the FTC-standard. At this level the music will be in the state of constant clip and is therefore the
highest power level one can obtain without completely obliterating the program material.
Lastly, the "normal operating power", as defined by EN 60065 as a measurement level for approval and testing to
this standard. The normal operating power is measured using pink noise, with an average output power equal to
1/8 of full power. The one-eighth power is the maximum volume music can be re- played without continuous
amplifier clipping this corresponds to headroom of only 9dB's, which is very low for normal program material.
6.5.1 Calculation
The current draw can be calculated by dividing the mains input power by the mains voltage.
We recommend that you design the power distribution for at least the required current at 1/8 power, and 1/3 power
for heavy-duty demands such as concert touring and Industrial music etc.
The heat power can be calculated as follows:
If a headroom figure of 9dB is used with a 4 ohms load on each output of the amplifier. The 1/8 power per channel
is 320 / 8 = 40 watts, and the total output power = 2 x 40 = 80 watts.
The mains power consumption from the chart above is then 370 watts.
Power 1/3 Power 1/8 Power Idle
[W] note 1note2
MA900 8 ohms 2x 200 345 235 60
4 ohms 2x 320 570 370 60
2 ohms 2x 470 930 585 60
note 1 Average power with music as program source. The amplifier driven to clip level.
note 2 Normal music power with 9dB headroom, IEC standard power rating.
MAX OUTPUT POWER MAINS INPUT POWER
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Martin Audio – MA900 Amplifier
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The heat power produced is the difference between the power consumption and output power;
370 - 80 = 290 watts total for the amplifier.
MA900 HEAT POWER
1/3 POWER 1/8 POWER 1/3 POWER 1/8 POWER 1/3 POWER 1/8 POWER
WATTS Kcal/hour BTU/hour
8 Ohm 307 235 260 200 1050 800
4 Ohm 453 370 390 320 1550 1260
2 Ohm 705 605 610 520 2410 2060
1/3 Power level = Average power with music as programme source. The amplifier driven to clip level
1/8 Power level = Normal operating power with music as programme source, 9dB headroom
7CONNECTIONS
7.1 Input connections
7.1.1 Balanced inputs
The input connectors are Neutrik combo jacks and incorporate an XLR and _" (6.3mm) jack. They are active balanced
and wired :
PIN 1 GROUND/SHIELD
PIN 2 HOT (+)
PIN 3 COLD (-)
XLR input connector XLR balanced
TIP HOT
RING COLD
SLEEVE SHIELD/GROUND
_” TRS plug
The input
impedance is
high enough
(20 K ohms
balanced) to
allow ”daisy-
chaining”, or
multiple parallel
input
connections.
The headroom of the input circuits is also high enough
to accept the maximum output level from virtually any
low-level signal source. Balanced signals are less
sensitive to AC hum and radio interference. The
source impedance should be less than 1 Kohms to
avoid high frequency losses in long cables.
To daisy chain amplifiers, use the screw-terminal
(Phoenix connector), labeled Link, provided on each
channel. It is connected in parallel with the Neutrik
Combo
j
ack on each in
p
ut.
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7.1.2 Unbalanced inputs
To use an unbalanced source, connect pin 3 (ring on
TRS jack) to the shield of the connector. If you leave
one pin disconnected, you will lose 6 dB.
A better method for using unbalanced sources is
shown below. This is similar to the connection for
balanced lines, but pin 3 is connected to the shield at
the source. The hum and noise rejection for the cable
is equivalent to that for a balanced line. To minimize
hum in the audio, use balanced inputs whenever
possible.
Unbalanced line connection
Balanced line with unbalanced equipment
For two-channel (stereo) operation, use both channels A and B. For tandem stereo or bridged mono operation, use
only one of the inputs. See operating modes for more details.
7.2 Connecting speakers
Speaker connections are made via the two Neutrik NL4FC Speakon connectors. The Speakon connector is designed
for high powe r l o u d s p eaker use and meets all worldwide safety requirements.
The Speakons are wired:
Channel A output
Pin +1, Pin -1 = Output A
Pin +2, Pin -2 = Output B
Channel B output
Pin +1, Pin -1 = Output B
The right Speakon, Channel A, has both channel A and B outputs available, and is useful for bridging and bi-amp
operation (see bridged mono operation on page 7). The left Speakon, Channel B, carries only the channel B
output.
Channel A and B into two separate
Speakons.
Channel A and B into one Speakon
(Stereo and Bi-amp)
Bridged mono
Never connect either output terminal to ground or to some other output or input terminal.
For normal two-channel operation, connect each speaker load across the output’s positive and negative terminals.
Pay attention to loudspeaker polarity; loudspeakers connected out of polarity can degrade sound quality.
Keep the loudspeaker cable as short as possible and use a good quality stranded cable. Do not use shielded wire,
such as microphone or guitar cable. The loudspeaker cable reduces the power of the amplifiers in two ways:
It increases the load impedance and introduces resistive power losses.
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Martin Audio – MA900 Amplifier
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MA9 0 0
-40dB
CLIP
PR O T EC T
ON
WARNING: To prevent electric shock, do not operate the amplifier with any of the loudspeaker cable
conductors exposed.
8OPERATION
8.1 Operating precautions
•Make sure that the power switch is set to “OFF” before connecting any input or output or operating the
switches on rear panel. See pages 8about installation.
•Make sure that the AC mains voltage is correct and the same as the one printed on the rear panel of the
amplifier. See pages 8, about operating voltage and power consumption.
•Make sure that the switches on the rear panel for operation modes, gain-switch and clip-limiter switch are
in the correct position. See page 6about operation modes and page 13 about clip limiters.
•It is always a good idea to turn down the gain controls during power-up, to prevent speaker damage in
case a high signal is present at the input.
8.2 Powering up – Soft start
•When you power up the amplifier it takes a couple of seconds to self-check. This is known as the "soft-start"
or "slow-start" sequence. The fans then blow at high speed before going into "idle" and the two bottom green
LED’s illuminate to show the amplifier is operational.
8.3 Input attenuators
The two input level attenuators on the front panel adjust the signal level for their respective amplifier channel in all
modes. They are calibrated in dB’s to help setting up active loudspeaker systems.
In bridged mode, both controls must be in the same position, so that the loudspeaker load will be shared equally
between the channels.
8.4 Indicators
The yellow LED's at the top indicate if any protection
circuits are activated. These are described on page13
The Clip/limit LED's indicate when the amplifier output is
clipping or limiting. It has two different indication states
•When the clip limiter is engaged it has a short time
constant and illuminates briefly.
•When the clip limiter is not engaged it has an
increased time constant and it illuminates for a longer
period.
The ”-40 dB” LED’s illuminate if the output signal is greater than -40dB (with 0dB as reference to full output power).
These LED’s also act as signal present indicators.
The two bottom green ”ON” LED’s indicate when the power supply and the output circuits are receiving the correct
rail voltage.
9PROTECTION FEATURES
Each MARTIN AUDIO MA series amplifier has many advanced protection features, that will protect both the amplifier
and the loudspeakers connected to it, should a fault condition arise.
Under normal use these features are inaudible. All protection circuits operate independently.
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Martin Audio – MA900 Amplifier
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9.1 Output Limiter
An output limiter is included to avoid amplifier clipping. When an amplifier is severely overdriven, its output waveform
is clipped (its peaks are squared off) – reducing the crest factor. In extreme cases, the waveform can ap p r o a c h t h a t o f
a square wave. An amplifier is usually capable of producing far more power under these conditions than its normal
undistorted rated output power.
The limiter works by monitoring the output and comparing the distortion produced between the input and output of the
amplifier. If the distortion exceeds 1%THD for any reason (voltage or current clipping), the limiter reduces the input
signal proportionally. Note that, if the signal is distorted or clipped before it reaches the amplifier, the clip limiter will not
be activated.
Under normal operation the clip limiter is inaudible. The limiter can be turned “On” or “Off” by pressing the relevant clip
limit switch. (3 page 5)
Some manufacturers of loudspeaker processors do not recommend the use of clip limiters in amplifiers, as they tend
to upset the tracking of the processor's limiters.
If the amplifier is being used without any external limiting, Martin Audio recommend leaving the clip limiters
switched "ON" (button depressed).
When the amplifier is driven very hard into a low impedance load, the cooling fans will run at high speed. If these
operating conditions continue, the Protect indicator(s) will illuminate indicating that the amplifier is about to go into
thermal shutdown.
After five seconds the amplifier will go into thermal protect by muting the input signal. After 15-20 seconds the
amplifier will have cooled down enough for the amplifier to come out of shutdown and operate as normal. If the load
conditions remain unchanged the thermal protection will be re - initiated. Thermal protection occurs when the heatsink
temperature reaches 90°
C.
9.2 VHF protection
If a signal of more than 12kHz, at full power is detected, which lasts for more than five seconds, the VHF protection
mutes the input signal. (This is indicated on the front panel (4) by the protect LED). After five seconds the outputs
will un-mute and return to normal operation, unless the output signal has remained unchanged, in which case the
VHF protection will re-initiate.
9.3 Short circuit protection
All MARTIN AUDIO MA Series amplifiers are completely short circuit protected. The protection circuit permits very
high peak currents, but still holds the output devices within the safe operating area. If a short circuit is maintained,
the channel affected will eventually go into a thermal protect cycle until the short circuit has been removed.
9.4 AC mains voltage protection
If the AC mains voltage is outside the operational window (over or under voltage), the power supply will
automatically shut down. When the mains voltage is above the minimum start voltage and below its maximum
operating voltage the amplifier will restart.
The two green ”ON” LED’s indicate when the power supply is operating properly.
9.5 DC protection
There are two types of DC protection:
•Fuses on the supply branches of each channel.
•DC crowbar protection that shorts the output if more than 10 volts DC is being detected on the outputs. Both
these circuits come int o e f f e c t o n c e a D C l e v e l is detected on either channel.
10 MAINTENANCE
Under normal use the amplifier should provide years of trouble-free service. The only maintenance required by the
user is to clean the front grill periodically.
In some extreme cases it may be necessary for authorized service personnel to clean the inside of the amplifier.
These conditions usually occur after prolonged use, e.g. in environments using "cracked- oil" smoke machines.
If you are using your amplifier for heavy-duty use i.e. concert touring or industrial music it is recommended that you
have your amplifier serviced every 3 years, purely as a preventative measure.
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Martin Audio – MA900 Amplifier
ENGLISH
14
10.1 Troubleshooting
These are typical things to check if you think your amplifier is faulty:
Fault: No output.
If the Signal Present LED (-40dB) is illuminating a signal is entering the amplifier and the likely cause is an
unsecured Speakon speaker connector, or loose termination.
Check also that the VHF protection is not activated. If it is, remove the cause of the possible high frequency
oscillations from the relevant input.
Fault: The amplifier goes into thermal protection when driven at low level.
Check that there is no short circuit present at the amplifier's output, e.g. any component in the loudspeaker (this
can occur when the speaker coil gets warm).
Fault: The amplifier goes into protection with power indicators off.
Check that the AC mains voltage is within the amplifier’s operating range, 130-265V @ 230V, and (65-135V @
115V). Over/under-voltage protection may have occurred. If the amplifier is connected by mistake to a 3-phase
supply, an internal non-resetable fuse or resistor may have blown. The amplifier then has to be returned to your
supplier for service.
Fault: The amplifier does not respond even after checking above items.
In the unlikely event of on a non-user rectifiable fault, return the amplifier to your supplier or an approved service
centre.
Martin Audio cannot be held responsible for damage or injury as a result of the top cover being removed.
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Martin Audio – MA900 Amplifier
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15
11 WARRANTY
General
The MA900 Power amplifier is warranted to be free from defects in components and factory workmanship under
normal use and service, for a period of three years from the date of original purchase. During this warranty period
MARTIN AUDIO LTD or it's nominated agents, will undertake to repair, or at it's discretion, replace this product at
no charge to it's owner, when failing to perform as specified, providing the unit is returned undamaged, in it's
original packaging, shipping prepaid, to the factory, distributor or authorised service facility.
This warranty shall be null and void, if the product is subjected to:
1) Repair work or alteration by persons other than those authorised by MARTIN AUDIO LTD
or it's agents.
2) Shipping accidents, act of god, war, civil insurrection, misuse, abuse, operation with incorrect AC voltage,
operation with faulty associated equipment, exposure to inclement weather conditions and normal wear
and tear. Units on which the serial number has been removed or defaced will not be eligible for warranty
service.
3) MARTIN AUDIO LTD shall not be responsible for any incidental or consequential damages, with respect to
the products warranted.
MARTIN AUDIO LTD reserve the right to make changes or improvements in design or manufacturing, without
assuming any obligation to change or improve products previously manufactured.
This warranty is exclusive and no other warranty is expressed or implied.
This warranty does not effect your statutory rights.
International
Please contact your supplier for this information, as rights and disclaimers may vary from country to country.
Technical assistance and services
If your Martin Audio product needs repair, contact your Martin Audio dealer or distributor, or contact Martin Audio
to obtain the location of the nearest dealer or distributor.
Telephone: [phone]
Fax: + 44 (0) 1494 438669
E mail: [email protected]
www.martin-audio.com
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Martin Audio – MA900 Amplifier
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16
12 SPECIFICATIONS MA900
MAXIMUM OUTPUT POWER EIA @1kHz 1%thd FTC 20 – 20kHz @ 0.1% thd
8Ωper Channel 300W 280W
4Ωper Channel 500W 460W
2Ωper Channel 700W 660W
8ΩBridged 1000W 920W
4ΩBridged 1400W 1320W
MAXIMUM OUTPUT VOLTAGE
8Ωload 49Vrms
Peak voltage, no load 77Vrms
POWER REQUIREMENTS 230V version 115V version
Operating voltage 130 – 265 Vac 65 – 135Vac
Minimum start up voltage 190Vac 95Vac
Peak inrush current 20A 10A
MAINS CURRENT DRAW @ 4 Ohms 230Vversion 115V version
Quiescent current (no load) 0.6Arms 1.2Arms
1/8th Full power (both channels driven) 3.5Arms 7Arms
1/3rd Full power (both channels driven) 5.5Arms 11Arms
Full power (1Khz @1% thd) 9.5Arms 19 Arms
DISTORTION
THD 20Hz – 20KHz 1W to full power 0.03%
THD @ 1KHz 1dB below clip 0.005%
DIM 30 @ 3dB below clip 0.008%
HUM / NOISE < - 105dB
CHANNEL SEPERATION -70dB
OUTPUT IMPEDANCE 30mΩ
SLEW RATE 45VµS
INPUTS
DIP switch selectable gain dB
Input Vrms Ref 4Ωfor full power
Impedance 20KΩDifferential
10KΩSingle ended
c.m.r.r 50dB
DIMENSIONS (W) 483mm x (H) 88mm x (D) 359mm
(W) 19ins x (H) 3.5ins x (D) 14.1ins
WEIGHT 15Kg (33Ibs)
SHIPPING DIMENSIONS (W) 560mm x (H) 180mm x (D) 500mm
(W) 22ins x (H) 7.1ins x (D) 19.7ins
SHIPPING WEIGHT 16.6Kg (36.5lbs)
20 23 26 29 32 35 38 41
3.58 2.53 1.79 1.27 0.90 0.64 0.45 0.32
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Martin Audio – MA900 Amplifier
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17
FRONT PANEL
Gain controls 2 x 31 Position detent
Indicators Protect 2 x Yellow LED’s
Indicators Clip 2 x Red LED’s
Indicators Signal Present 2 x Green LED’s
REAR PANEL
Input Connectors 2 x Neutrik Combo, + 3 pin Phoenix
Output Connectors 2 x Neutrik Speakons
Clip Limiters Push Switch “ON”/ ”OFF” per Channel
Speakon¸and Combºjack, are registered Trademarks of Neutrik AG Liechtenstein
All material © 2007. Martin Audio Ltd. Subject to change without notice.

MA900 Amplifier
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MA900 Amplifier
User’s Guide
All material © 2007. Martin Audio Ltd. Subject to change without notice.