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Operating Instructions
TOA 900 SERIES II
A-903MK2
A-906MK2
MIXER POWER AMPLIFIER
A-912MK2
THE LIGHTNING FLASH WITH
ARROWHEAD WITHIN A TRIANGLE IS
INTENDED TO TELL THE USER THAT
PARTS INSIDE THE PRODUCT ARE A
RISK OF ELECTRIC SHOCK TO
PERSONS.
TO REDUCE THE RISK OF ELECTRICAL
THE EXCLAMATION POINT WITHIN A
SHOCK, DO NOT REMOVE COVER. TRIANGLE IS INTENDED TO TELL
THE USER THAT IMPORTANT
NO USER SERVICEABLE PARTS INSIDE.
OPERATING AND SERVICING
REFER SERVICING TO QUALIFIED
INSTRUCTIONS ARE IN THE P
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Contents General description 3 Features 3 Nomenclature 4 Front panel Rear panel 5 Input connections 6 Output connections (A-903MK2) 6~7 Output connections (A-906MK2/A-912MK2) 7~8 8 Muting and remote volume control connection Rack mounting 8 Operation 9 Volume adjustment 9 Tone control adjustment 9 Installation 9 9 Servicing 10 Specifications Appearance (A-903MK2) 11 12 Appearance (A-906MK2/A-912MK2) –2–
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General Description The TOA A-903MK2, A-906MK2 and A-912MK2 Mixer Power Amplifiers control and mix up to eight independent input signals. The A-903MK2 delivers up to 30 watts of output power, the A-906MK2 60 watts and A-912MK2 120 watts. Optional plug-in modules are available for use with these mixer power amplifiers to provide versatility for a wide range of operating applications. Edge connectors on the rear of the unit permit the selection of the TOA plug-in modules. The mixer power amplifier
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Nomenclature Front Panel Power Switch Input Volume Controls Applies line power. Two-position push button Adjust gain of input #1 ~#8 respectively. switch for on/off modes. Bass Control Power Indicator LED Modifies bass response. Turn clockwise to boost, Green LED lights when the power is switched counter-clockwise to attenuate the bass "ON". response. Tone is flat at center. Signal Indicator LED Treble Control Green LED lights when more than –30 dB signal Modifies treble response. Turn clockwise
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Rear Panel AC Power Cord Preamp Out Connects to power source. Connects to a signal processing equipment such as a limiter, an equalizer, etc. The input AC Outlet (Unswitched) impedances of the equipment should be of more Provides AC power for auxiliary equipment with than 600 ohms. power consumption of up to 500W. Bridging Input/Output This terminal is used as a mixing bus. Mixing is Output terminals Connect to speakers. achieved when the similar terminal of another amplifier is connected to thi
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Input Connections There are eight INPUT PORTS for PLUG-IN MODULES. Select the desired modules for each application. Plug the modules into the INPUT PORTS. Slide them between the guide rails and secure with two screws. CAUTION : Modules should not be inserted or removed while the amplifier is turned on. Cover unoccupied INPUT PORTS with blank panels. Secure blank panels with screws. Output Connections (A-903MK2) The speaker outputs of the amplifier are 4 ohms, 8 ohms, 25V and 70V. Connect speaker
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To connect speakers to 8-ohm output (UNBALANCED DIRECT OUTPUT) (A-903MK2) 8-ohm Loosen the screw. Place the impedance switch in 8-ohm position. Tighten the screw. Output Connection (A-906MK2/A-912MK2) The speaker outputs of the amplifier are 4 ohms, 8 ohms, 25V and 70V. Connect speakers to any one of these outputs. Class 2 wiring may be used. There are two types of output ; 8 ohms, 25V and 70V via output (matching) transformer •4-ohm direct output. The connecting method differs in each case. Ref
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To connect speakers to 4-ohm output (UNBALANCED DIRECT OUTPUT) (A-906MK2/A-912MK2) 4-ohm Loosen the screw. Place the impedance switch in 4-ohm position. After all connections are made, tighten the screw. Muting and Remote Volume Control Connection POTENTIOMETER 10k OHMS MUTE 2 MUTE 1 Remote volume control connection limiting front panel master volume control range. Rack Mounting To mount the amplifier in a standard 19" equipment rack, use the optional MB-25B rack mounting bracket. MB-25B Remove
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Operation After all connections are made, turn power switch ON, illuminating the Power Indicator LED. The amplifier comes into operation approximately 5 seconds after the power is turned on. Volume Adjustment Obtain desired output level by adjusting the individual input and master volume controls. For normal music playing or announcement, adjust volume using their controls until the normal LED intermittently lights. Sound quality is deteriorated when the peak LED remains lit. Tone Control Adjust
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Specifications A-903MK2 A-906MK2 A-912MK2 Type 8-channel mixer power amplifier Output Power 30W RMS 60W RMS 120WRMS (D) 20 ~20,000 Hz, 0.5% THD Power Band Width (T) 50 ~20,000 Hz, 0.5% THD (D) 20 ~20,000 Hz, ± 1 dB Frequency Response (T) 20 ~15,000 Hz, ± 1 dB (T) 20 ~20,000 Hz, +1 dB, -3 dB Total Hamonic Distortion 0.02% at 1 kHz, rated output Eight Input Ports : Each port accepts any input module. Inputs One Bridging Input/Output Input Port #1 to #8 : 100 mV/10k ohms Input Sensitivity/Impedance
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Appearance (A-903MK2) Front View 420 Rear View Top View Side View –11– 17 280 318
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Appearance (A-906MK2/A-912MK2) Front View 420 Rear View Top View Side View TOA Corporation PRINTED IN TAIWAN KOBE, JAPAN 133-12-114-60 88.4 99.1 17 320 358
