Toa A-903MK2 User manual

TOA 900 SERIES II
MIXER POWER AMPLIFIER
Operating Instructions
A-903MK2
A-906MK2
A-9 2MK2
TO REDUCE THE RISK OF ELECTRICAL
SHOCK, DO NOT REMOVE COVER.
NO USER SERVICEABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED
SERVICE PERSONNEL.
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.
THE EXCLAMATION POINT WITHIN A
TRIANGLE IS INTENDED TO TELL
THE USER THAT IMPORTANT
OPERATING AND SERVICING
INSTRUCTIONS ARE IN THE PAPERS
WITH THE APPLIANCE.
Plea e follow the in truction in thi manual to obtain the optimum re ult from thi unit.
We al o recommend that you keep thi manual handy for future reference.
TOA Corporation

Contents
General de cription
Feature
Nomenclature
Front panel
Rear panel
Input connection
Output connection (A-903MK2)
Output connection (A-906MK2/A-912MK2)
Muting and remote volume control connection
Rack mounting
Operation
Volume adju tment
Tone control adju tment
In tallation
Servicing
Specification
Appearance (A-903MK2)
Appearance (A-906MK2/A-912MK2)
3
3
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 Amplifier control and mix up to eight
independent input ignal . The A-903MK2 deliver up to 30 watt of output power, the A-906MK2 60 watt
and A-912MK2 120 watt .
Optional plug-in module are available for u e with the e mixer power amplifier to provide ver atility for a
wide range of operating application . Edge connector on the rear of the unit permit the election of the TOA
plug-in module .
The mixer power amplifier have output terminal to match 4- or 8-ohm peaker y tem , or peaker
di tribution y tem may be connected to 25- or 70-volt terminal , and can be rack mounted by u ing
optional rack mounting bracket MB-25B. The optional perforated panel PF-511 provide uitable ventilation,
fini hed in color to match the mixer power amplifier .
Features
1. 8-channel mixer power amplifier
2. Wide frequency re pon e : 20~20,000 Hz ± 1 dB
3. Low di tortion and noi e level
4. Remote ma ter volume control
5. Excellent output regulation
6. Ba and treble control
7. Bridging input/output
8. Self-protection circuitry de ign
9. Signal proce ing input/output
10. Varied output impedance : 4 ohm , 8 ohm , 25 and 70 volt
11. A full range of plug-in module
12. Portable or rack mounting type
–3–

Nomenclature
Front Panel
Power Switch
Applie line power. Two-po ition pu h button
witch for on/off mode .
Power Indicator LED
Green LED light when the power i witched
"ON".
Signal Indicator LED
Green LED light when more than –30 dB ignal
level i fed to the input by mean of the input
and ma ter volume control .
Normal Indicator LED
Yellow LED light when fed to the proper ignal
level.
Peak Indicator LED
Red LED light when amplifier approache
clipping level. If teady lit, the input level control
hould be turned down until the LED fla he only
intermittently.
Protection Indicator LED
Remain lit for about 5 econd after power
witch i turned ON.
Input Volume Controls
Adju t gain of input #1 ~#8 re pectively.
Bass Control
Modifie ba re pon e. Turn clockwi e to boo t,
counter-clockwi e to attenuate the ba
re pon e. Tone i flat at center.
Treble Control
Modifie treble re pon e. Turn clockwi e to
boo t, counter-clockwi e to attenuate the treble
re pon e. Tone i flat at center.
Tone Switch
Select ON/OFF of the BASS and TREBLE
control . When lided to OFF, BASS and
TREBLE control are active. When lided to ON,
they become inactive to make tone flat.
Low-Cut Switch
Cut off unnece ary low frequency.
Master Volume Control
Adju t overall gain of the unit.
–4–

Rear Panel
AC Power Cord
Connect to power ource.
AC Outlet (Unswitched)
Provide AC power for auxiliary equipment with
power con umption of up to 500W.
Output terminals
Connect to peaker .
Impedance Select Switch
Select the de ired impedance.
Enable unbalanced output of low impedance
when thi witch i et to "DIRECT".
Module Input Ports
Accept optional PLUG-IN MODULES.
Module election i determined by application.
For detail , refer to Plug-in Module In truction
Manual.
AUX Out
Provide connection for a boo ter amplifier or
tape recorder.
The input impedance of the equipment hould be
of more than 10k ohm .
Power Amp In
Connect to acce ory equipment.
Preamp Out
Connect to a ignal proce ing equipment uch
a a limiter, an equalizer, etc. The input
impedance of the equipment hould be of more
than 600 ohm .
Bridging Input/Output
Thi terminal i u ed a a mixing bu . Mixing i
achieved when the imilar terminal of another
amplifier i connected to thi terminal. The output
level taken from thi terminal i independent of
Ma ter Volume Control, Ba and Treble
Control o that the terminal can al o be u ed a
recording output.
The input impedance of the equipment to be
connected here hould be of more than 10k
ohm .
Remote Volume Control Terminals
Connecting a 10k linear taper potentiometer
acro the e terminal will allow remote control
of preamplifier output.
Mute terminals
Mute input ignal fed to plug-in module
employing muting function by hort-circuiting at
the e terminal .
–5–

Input Connections
There are eight INPUT PORTS for PLUG-IN MODULES.
Select the de ired module for each application. Plug the module
into the INPUT PORTS.
Slide them between the guide rail and ecure with two crew .
CAUTION : Module hould not be in erted or removed while
the amplifier i turned on.
Cover unoccupied INPUT PORTS with blank panel . Secure blank panel with crew .
Output Connections (A-903MK2)
The peaker output of the amplifier are 4 ohm , 8 ohm , 25V and 70V.
Connect peaker to any one of the e output .
Cla 2 wiring may be u ed.
There are two type of output;
4 ohm , 25V and 70V via output (matching) tran former
8-ohm direct output.
The connecting method differ in each ca e. Refer to the following diagram .
Note : Impedance indicated below imply total peaker y tem (load) impedance .
To connect speakers to outputs of : 4 ohms, 25V or 70V (BALANCED OUTPUT)
(A-903MK2)
4-ohm
21-ohm
25V line
167-ohm
70V line
Loo en the crew.
Place the impedance witch in 4-ohm po ition.
Tighten the crew.
Note : Low-cut witch hould be in "CUT" po ition.
Cut off unnece ary low frequency in TRANS OUTPUT to obtain be t acou tic condition. The
900MK2 erie amplifier are characteri tically flat even in the low frequency range. Thu , in TRANS
OUTPUT the acou tic effect and frequency-re pon e characteri tic may be altered.
–6–

To connect speakers to 8-ohm output (UNBALANCED DIRECT OUTPUT)
(A-903MK2)
8-ohm
Loo en the crew.
Place the impedance witch in 8-ohm po ition.
Tighten the crew.
Output Connection (A-906MK2/A-912MK2)
The peaker output of the amplifier are 4 ohm , 8 ohm , 25V and 70V.
Connect peaker to any one of the e output .
Cla 2 wiring may be u ed.
There are two type of output ;
8 ohm , 25V and 70V via output (matching) tran former
•4-ohm direct output.
The connecting method differ in each ca e. Refer to the following diagram .
Note : Impedance indicated below imply total peaker y tem (load) impedance .
To connect speakers to outputs of : 8 ohms, 25V or 70V (BALANCED OUTPUT)
(A-906MK2/A-9 2MK2)
8-ohm
10.4-ohm(A-906MK2)/
5.2-ohm(A-912MK2)
25V line
83-ohm(A-906MK2)/
41-ohm(A-912MK2)
70V line
Loo en the crew.
Place the impedance witch in 8-ohm po ition.
Tighten the crew.
Note : Low-cut witch hould be in "CUT" po ition.
Cut off unnece ary low frequency in TRANS OUTPUT to obtain be t acou tic condition. The
900MK2 erie amplifier are characteri tically flat even in the low frequency range. Thu , in TRANS
OUTPUT the acou tic effect and frequency-re pon e characteri tic may be altered.
–7–

To connect speakers to 4-ohm output (UNBALANCED DIRECT OUTPUT)
(A-906MK2/A-9 2MK2)
4-ohm
Loo en the crew.
Place the impedance witch in 4-ohm po ition.
After all connection are made, tighten the crew.
Muting and Remote Volume Control Connection
MUTE 2 MUTE 1
POTENTIOMETER
10k OHMS
Remote volume control connection limiting
front panel ma ter volume control range.
Rack Mounting
To mount the amplifier in a tandard 19" equipment rack, u e the optional MB-25B rack mounting bracket.
Remove 4 crew ecuring ca e.
MB-25B
Fix the bracket with attached 4 crew . The length
of crew hould not exceed 12mm (1/2").
Amplifier
PF-511 perforated panel (1-unit ize)
U e the perforated panel PF-511 to provide pace for ventilation,
when two or more unit are mounted in an equipment rack.
Contact your local TOA dealer for the perforated panel PF-511.
–8–

Operation
After all connection are made, turn power witch ON, illuminating the Power Indicator LED. The amplifier
come into operation approximately 5 econd after the power i turned on.
Volume Adjustment
Obtain de ired output level by adju ting the individual input and ma ter volume control . For normal mu ic
playing or announcement, adju t volume u ing their control until the normal LED intermittently light . Sound
quality i deteriorated when the peak LED remain lit.
Tone Control Adjustment
Set the tone witch to the OFF po ition. Thi activate the ba and treble control . The frequency re pon e
characteri tic of each control are flat at center, boo t in CW and attenuation in CCW po ition . When tone
control are unnece ary, et the tone witch to ON mode.
Installation
Never block ventilation hole .
The amplifier hould never be placed in area
expo ed to direct unlight.
with high humidity or du t level .
with high ambient temperature .
u ceptible to vibration.
with poor ventilation.
adjacent to heat-generating equipment.
CAUTION : Do not remove the ca e or you may encounter an electric hock.
Note : When the temperature of heat ink exceed 105 °C the protection circuit i activated and the output i
di connected from the circuit. Output i automatically re tored when the temperature return to normal
operating parameter.
Servicing
Unpacking
Upon receipt of the amplifier hipment, plea e in pect for any damage incurred in tran it. If damage i
found, plea e notify your local TOA repre entative and the tran portation company immediately.
State date, nature of damage, whether any damage wa noticed on the hipping container, prior to
unpacking.
Plea e give waybill number of hipping order.
Failure
Should amplifier fail, contact your neare t TOA authorized contractor or ervice center.
–9–

Specifications
Type
Output Power
Power Band Width
Frequency Re pon e
Total Hamonic Di tortion
Input
Input Sen itivity/Impedance
Preamp OUT/Power Amp IN
Output (T)=Tran former
(D)=Direct
Output Regulation (1 kHz)
Signal to Noi e Ratio
(Band Pa 20 ~20,000 Hz)
Tone Defeat SW ON
Tone Control
Control
Indicator
Protection
Connector
Power Con umption
Temperature Range
Dimen ion (W) x (H) x (D)
Weight
Color
Standard Acce orie
Other Feature
A-903MK2 A-906MK2 A-9 2MK2
8-channel mixer power amplifier
30W RMS
60W RMS 120WRMS
(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
0.02% at 1 kHz, rated output
Eight Input Port : Each port accept any input module.
One Bridging Input/Output
Input Port #1 to #8 : 100 mV/10k ohm
Bridging Input/Output: 100 mV/3.3k ohm
1000 mV into 600 ohm /1000 mV, 10k ohm
Main (T): 4 ohm , 25
& 70 volt , balanced
Main (D): 8 ohm ,
unbalanced
Aux : 10k ohm , 1V
Main (T) : 8 ohm , 25 & 70 volt , balanced
Main (D) : 4 ohm , unbalanced ,
Aux : 10k ohm , 1V
(D) Le than 0.5 dB, no load to full load
(T) Le than 1.0 dB, no load to full load
Ma ter volume min : 90 dB
Ma ter volume max : 77 dB
Power amplifier only : 105 dB
Ba : ± 10 dB at 100 Hz, Treble : ± 10 dB at 10 kHz
8 Input gain control 1 Ma ter gain control
1 Ba tone control 1 Treble control
1 Power ON/OFF witch 1 Tone defeat witch
1 Low-Cut witch (60 Hz, 6 dB/octave)
1 Power LED, 1 Protect LED, 1 Signal LED, 1 Normal LED, 1 Peak LED
Self-protection, with AC fu e (in ide)
Input No.1 to No.8
Bridging, Mixer preamp. output
Power amp. input, Aux output
Output
Mute, Remote VR
AC power cord/plug
AC outlet
Card-edge connector
RCA phono jack
Screw-terminal trip
Screw-terminal trip
SJT, 3-prong type
3-pin grounding type
60 W
-10 °C ~ +60 "C [12°F~140°F]
100W
180W
420 x 99.1 x 318 mm
[16.5 X3.9X 12.5 in.]
7.8 kg [17.2 Ib.]
420 x 99.1 x 358 mm
9.6kg [21.2lb.]
[16.5 X3.9X 14.1 in.]
11. 4 kg [25.1 Ib.]
Black
4 Volume control cover (YA-920)
Output di connected for approx. 5 econd after witching power on.
* Specification are ubject to change without notice.
–10–

Appearance (A-903MK2)
Front View
Rear View
Top View Side View
420
280 318
17
–11–

Appearance (A-906MK2/A-9 2MK2)
Front View
420
Rear View
Top View Side View
88.4
99.1
320 358
17
TOA Corporation
KOBE, JAPAN
PRINTED IN TAIWAN
133-12-114-60