Operating Instructions TOA 900 SERIES II MIXER POWER AMPLIFIER A-903MK2 A-906MK2 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 SHOCK, DO NOT REMOVE COVER. NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
Contents 3 3 General description Features Nomenclature Front panel Rear panel Input connections Output connections (A-903MK2) Output connections (A-906MK2/A-912MK2) Muting and remote volume control connection Rack mounting Operation Volume adjustment Tone control adjustment Installation Servicing Specifications Appearance (A-903MK2) Appearance (A-906MK2/A-912MK2) 4 5 6 6~7 7~8 8 8 9 9 9 9 9 10 11 12 –2–
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.
Nomenclature Front Panel Power Switch Input Volume Controls Applies line power. Two-position push button switch for on/off modes. Adjust gain of input #1 ~#8 respectively. Bass Control Power Indicator LED Green LED lights when the power is switched "ON". Modifies bass response. Turn clockwise to boost, counter-clockwise to attenuate the bass response. Tone is flat at center.
Rear Panel AC Power Cord Connects to power source. AC Outlet (Unswitched) Provides AC power for auxiliary equipment with power consumption of up to 500W. Preamp Out Connects to a signal processing equipment such as a limiter, an equalizer, etc. The input impedances of the equipment should be of more than 600 ohms. Bridging Input/Output Output terminals Connect to speakers. Impedance Select Switch Selects the desired impedance.
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.
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.
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 MUTE 2 MUTE 1 10k OHMS 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.
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.
Specifications A-903MK2 Type Frequency Response A-912MK2 60W RMS 120WRMS 8-channel mixer power amplifier Output Power Power Band Width A-906MK2 30W RMS (D) 20 ~20,000 Hz, 0.5% THD (T) 50 ~20,000 Hz, 0.5% THD (D) 20 ~20,000 Hz, ± 1 dB (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 Inputs Eight Input Ports : Each port accepts any input module.
Appearance (A-903MK2) Front View 420 Rear View Top View 17 –11– 318 280 Side View
Appearance (A-906MK2/A-912MK2) 99.1 88.
