Toa A-503A Instruction Manual

Operation Instruction Manual
TOA 500 SERIES
MIXER POWER AMPLIFIER
A-503A
A-506A
A-512A
Features
General Description
1. High quality design and construction.
2. Full frequency response: 50 - 15,000Hz, ±3dB.
3. Low distortion and noise level.
4. 4 microphone inputs, 3 auxiliary inputs and a mag. phono
input.
5. Isolated-transformer outputs complete with 4 ohms, 25V
and 70V.
6. AC/DC operation: 120V AC and 24V DC
7. Individual bass and treble tone controls.
8. Signal processing input/output.
9. Self-protection circuitry design.
10. Muting function.
11. Remote volume control circuit.
TheTOA 500 series Mixer Power Amplifiers A-512A, A-506A and
A-503A are designed for PA system applications such as paging,
announcements, intercommunications, background music and
broadcasting in industrial plants, offices, schools, churches,
department stores, shopping centers, night clubs, dining rooms,
convention halls, auditoriums and recreation areas.
The Primary feature is their ability to withstand overload or
short-circuits of output. Because of the TOA-engineered circuitry
design, the TOA 500 -series amplifiers require no complicated
protective circuit to withstand accidents and mismatched output
connections that may occur during the installation or use of a PA
system. This results in very high reliability.
The 500 series amplifiers come with 4 microphone inputs, 3
auxiliary inputs and a mag. phono input. Input 1 (Mic 1) and Input
2 (Mic 2) out of the 4 mic inputs are balanced inputs, while Input
3 (Mic 3) and Input 4 (Mic 4) are of unbalanced type. Input 3 and
Input 4 can be changed to balanced type with the LI-51
microphone input module (optional). Two condenser mic-
rophone can be used with phantom power supplied from Input 1
and 2. And they have a remote volume control circuit on Input 2
as the volume can be adjusted at the microphone even when it is
distant from the amplifier. The amplifiers are
equipped with
muting function.
They may be used in conjunction With a speaker rated at 4 ohms
or with 25volt, 70volt constant-voltage speaker systems.
Three auxiliary inputs and a mag. phono input are provided with
RCA pin jack. Preamp-Out and Power-Amp-ln receptacles are
provided for easy connection of a signal processor to the
amplifier.
Emergency operation can be made by DC power source (24V DC)
even in case of AC power failure.
TOA Corporation
KOBE, JAPAN
133-02-767-7A
Printed in Taiwan

TOA 500 SERIES
Front Panel Controls and Features
No.
1
2
3
4
5
6
Name
Power on-off switch
Power indicator
Input 1 - 5 volume controls
Bass control
Treble control
Master volume control
Function/Description
Applies line power. Two position button switch for on-off modes.
Comes on when power is turned on.
Adjusts gain of Input 1 - 5 respectively.
Adjusts bass response.
Turn clockwise (CW) to boost and counterclockwise (CCW) to attenuate
the bass response. Tone is flat at center.
Adjusts treble response.
Turn clockwise (CW) to boost and counterclockwise (CCW) to attenuate
the treble response. Tone is flat at center.
Adjusts overall gain of unit.
Block Diagram
A-503A, A-506A, A-512A
BLOCK DIAGRAM

No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Name
AC power supply cord
AC outlet (unswitched)
AC fuse
24V DC terminals
Output terminals
Input 1 (Mic 1),
Input 2 (Mic 2) inputs
Pahntom power ON/OFF switch
(Mic 1, Mic 2)
Input 3 (Mic 3), Input 4 (Mic 4) inputs
Input 3 (Mic 3/Mag. phono) select switch
Input 4 (Mic 4/Aux 1) select switch
Mag. phono input
Aux 1 - 3 inputs
Aux 3 volume control
Tape output
Booster output
Preamp output
Power amp input
Link switch
Remote volume control terminals
Mute terminals
(adjustable muted level: 0 - 30dB)
Earth terminal
Function/Description
Connects to AC power supply.
Provides AC power for auxiliary equipment with power consumption
of up to 500W.
Prevents excessive current flow.
Connect to DC power supply (24V).
Connect to speakers.
Connect to microphones of balanced 200 ohms with XLR
connectors.
This switch is to be turned on when using the condenser
microphone.
These screw terminal inputs connect to unbalanced 50k ohms
microphone.
Selects Mic 3 or Mag. phono input.
Selects Mic 4 or Aux 1 input.
Connects to the record player with MM type cartridge.
Connect aux inputs.
Adjusts gain of Aux 3.
Provides connections for a tape recorder. The input impedance of
the equipment should be more than 4.7k ohms.
Provides connections for a booster amplifier. The input impedance
of the equipment should be more than 600 ohms.
Connects to a signal processing equipment such as a limiter,
equalizer etc. The input impedance of the equipment should be
more than 600 ohms.
In this case, Link switch should be set the "OUT" position.
When using this terminal, set Link switch to "OUT".
Disconnects between preamplifier and power amplifier when this
switch is set to "OUT", allowing the connection of other equipment.
Mic 2 volume can be adjusted by means of a 10k-ohms
potentiometer connected to these terminals.
Short-circuiting these terminals mutes input signals (inputs 3-5).
Normally connects to record player's ground.
- 2 -

TOA 500 SERIES
Installation
Output Connections
CAUTION
Do not remove the cover to prevents an electric shock.
Input Connections
CAUTION
When connecting speakers to any one of the outputs of 4
ohms, 25V or 70V.
Do not block cover ventilation holes.
The amplifier should not be placed in areas;
1) with poor ventilation.
2) exposed to direct sunlight.
3) With high ambient temperature or adjacent to
heat-generating equipment.
4) with high humidity or dust levels.
5) susceptible to vibration.
Speaker output
The speaker outputs of the amplifier are 4 ohms, 25V, and 70V.
Connect the speakers cable to one of these outputs, after removing
the screw terminal cover. Put the cover back on when finished the
connection.
Class 2 wiring may be used.
Since these outputs consist of 4 ohms, 25V and 70V via the output
transformer (matching transformer) the connecting method differs in
each case.
See the following diagrams.
Note: Impedances indicated below imply total speaker system
(load) impedances.
(load) impedances.
<A-503A>
Output Terminal
<A-506A>
Output Terminal
A. Microphone
A. Microphone
Four microphone inputs are provided. Two of them may be used with
balanced low impedance (30 - 600 ohms) microphone, or with
condenser microphone. The other may be used with an unbalanced
high impedance (50k ohms) microphone. The microphone with the
unbalanced connection cable of 30 - 70ft or balanced cable 70 - 230ft
may be used depending on the microphone and its characteristic.
Mic 1 and Mic 2
1) for dynamic microphones — Low impedance (30 - 600 ohms)
balanced microphone inputs are provided with a XLR connector.
2) for condenser microphones - Condenser microphones can be
used with supplying DC 15V phantom power, while turning on the
phantom power switch above the mic input connector.
Mic 3 and Mic 4 — High impedance (50k ohms) unbalanced type
microphone inputs are provided with screw terminals.
Using Mic 3 input, the Input 3 select switch must be turned to Mic 3.
Using Mic 4 input, the Input 4 select switch must be turned to Mic 4.
B. Record player
Record player with MM (moving magnet type) cartridge may be
connected to Mag. Phono input (2mV, 50k ohms).
Use single or double conductor shielded cable with a terminating
RCA pin plug. It is recommended that a separate ground wire be
connected between the record player base and the earth ( )
screw terminal on the rear panel.
C. Radio tuner, cassette tape player and other BGM sources
A radio tuner, tape player, chime, mixer preamplifier, compact disk
player or other high level signal sources may be connected to the
AUX-1, AUX-2 or AUX-3 input.
Use single or double conductor shielded cable with a terminating
RCA pin plug.
<A-512A>
Output Terminal
- 3 -

Output Connections
DC Power Operation
Operation
CAUTION
The unit should be used only with negative-grounded vehicle
or frame when DC operation is required.
Do not use the unit with positive-grounded equipment of DC
operation.
Tape output
A tape recorder may be driven from the Tape output jack on the
amplifier. In this case, the output is not subject to the volume or tone
setting of the amplifier and is controlled at the tape recorder. A patch
cable terminated in a. standard pin plug is connected between the
Tape output jack on the amplifier and the input of the tape recorder.
Booster output
A booster amplifier may be driven from the Booster output jack on
the amplifier. In this case, the output is not subject to the volume or
tone setting of the amplifier and controlled at the booster amplifier. A
patch cable terminated in a standard pin plug is connected between
the Booster output jack on the amplifier and the input of the booster
amplifier.
Link switch
Provision is made to insert signal processing equipment into the
signal path, using the PREAMP OUT and POWER AMP IN.
Using signal processing equipments, LINK SWITCH must be turn-off.
The unit will also operate from an external 24V battery or other direct
current source with negative (-) as ground. Power connections are
made at the DC terminal strip on the rear panel.
If AC power supply fails, transfer to DC power is instantaneous,
automatic and silent.
The battery power supply is not operated by the primary power
switch. If switching of battery power is desired, an external relay or
switch should be installed by the qualified service personal.
When all connections are completed, turn power switch on.
Then the power indicator is illuminated when the amplifier is on.
Adjustment of volume
Adjust the individual input and the master volume control to obtain
appropriate output level.
Adjustment of tone quality
Each of the Bass and Treble control provides frequency-response
characteristics of flat in center, boost in clockwise and attenuation in
counterclockwise positions.
Connect the battery to DC terminal, after removing the screw
terminal cover.
Put the cover back on when finished the connection.
- 4 -
24V DC
Terminal
24V DC
Battery
24V DC

TOA 500 SERIES
CAUTION
Use the potentiometer of 10k ohms.
Make wiring lest the interference from external noise should
occur.
Short-circuiting the mute terminal on the rear panel mutes Input 3,
Input 4 and Input 5, allowing Input 1, Input 2 and Aux 3 to override the
muted inputs.
The signal attenuation amount is pre-adjusted to 30dB at the factory
and can be adjusted to 0 to 30 dB by means of muting level control.
Adjusting the muting level is with the muting level control volume on
bottom chassis as follows.
muting level control volume
(mounted on bottom surface)
Turn C.C.W.
Reduce attenuation
to 0 dB
Turn C.W.
Increase attenuation
to 30 dB
Mic 2 input provides the remote volume control, the circuit is
activated with a potentiometer 10k ohms connected to the remote
volume control terminal.
CONNECTIONS
MUTE MIC 2 REMOTE VOLUME
Mute terminal
and MIC 2
remote volume
terminal
Mute
Switch
Remote
volume
control
potentiometer
10k ohms
Signal
level
mute terminal
shorted.
2 - 3 sec.
INPUT 3
INPUT 4
INPUT 5
Attenuation
0 -30 dB
gradually
restored.
mute terminal opened.
Time
Unpacking
Upon receipt of the amplifier shipment, please inspect for any
damage incurred in transit. If damage is found, please notify local TOA
representative and the transportation company immediately.
State date, nature of damage, whether any damage was noticed on
the shipping container, prior to unpacking. Please give waybill
number of shipping order.
Failuer
Should amplifier fail, contact your nearest TOA authorized contractor
or service center.
- 5 -

Mic 3 and 4 are provided in one plug-in module. It can be replaced to
the optional mic input module "U-51".
If setting the U-51, XLR connectors may be provided with balanced
low impedance (30 - 600 ohms) from standard screw type terminals
with unbalanced high impedance (50k ohms).
OPTIONAL MIC INPUT MODULE "U-51"
** Replacing of mic input 3 and 4 **
1) Be sure to unplug the power cable from the wall AC outlet.
2) Unscrew the Mic 3 and Mic 4 input module and pull towards you.
3) Unplug a connector fitted to the mic input module and connect it to
the Mic input module "U-51"
4) Insert the U-51 and tighten two screws.
- 6 -
U-51

TOA 500 SERIES
Specifications
Type
Model
Power output
Output regulation
Outputs
Inputs
Frequency response
Total harmonic distortion
Signal to Noise Ratio
(Tone controls centered)
Tone controls
Controls
Indicator
Power supply
AC power consumption
DC power consumption
Other features
Dimensions
Weight
Color
Mixer Power Amplifier
A-503A
Rated : 30 watts
A-506A
Rated : 60 watts
Less than 2 dB, no load to full load
Speaker outputs : Balanced 4 ohms, 25 V and 70 V
Tape output : 4.7k ohms 650 mV
Booster output : 600 ohms 1 V
Preamp output : 600 ohms 1 V
A-512A
Rated : 120 watts
INPUT 1 : 200 ohms, 0.3 mV (MIC 1)
INPUT 2 : 200 ohms, 0.3 mV (MIC 2)
INPUT 3 : 50k ohms, 3 mV (MIC 3)/50k ohms, 2 mV (MAG. PHONO)
INPUT 4 : 50k ohms, 3 mV (MIC 4)/220k ohms, 100 mV (AUX 1)
INPUT 5 : 10k ohms, 100 mV (AUX 2)
AUX 3 : 10k ohms, 100 mV
Power amp input : 10k ohms, 1 V
50 - 15,000 Hz ±3 dB
Less than 2% at 1 kHz, rated power
All volume controls c.c.w.
Microphone (MIC 1, MIC 2)
AUX (AUX 2, AUX 3)
Mag. phono
: 80 dB below rated power
: 60 dB below rated power (200 ohms terminated)
: 70 dB below rated power
: 60 dB below rated power
Bass : ±10 dB at 100 Hz
Treble : ±10 dB at 10 kHz
INPUT 1 volume control
INPUT 2 volume control
INPUT 3 volume control
INPUT 4 volume control
INPUT 5 volume control
AUX 3 volume control
TONE controls (BASS, TREBLE)
MASTER volume control
Muting level control
Power indicator (LED)
120V AC 60 Hz and 24V DC
60 watts
2.1 A at rated power
100 watts
4.2 A at rated power
180 watts
7.5 A at rated power
Muting function Phantom power : 15V DC (MIC 1, MIC 2)
Remote volume control (MIC 2)
88.5mm (high) x 420mm (wide) x 280mm (depth)
(3.48" x 16.54" x 11.02")
7.1 kg
Black
8.1 kg
10.4 kg
* Specifications are subject to change without notice.
TOA Corporation
KOBE, JAPAN
- 7 -

- 8 -
Schematic A-503A

- 9 -
Schematic A-506A
TOA 500 SERIES

-10 -
Schematic A-512A