Operating Instruction Manual
TOA POWERED MIXER
ModelMX-104
TOA ELECTRIC CO., LTD.
KOBE, JAPAN
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General Description
The TOA MX-104 is a very compact, four channel self-powered mixer. It was
designed to deliver maximum features and performance in a cost-effective portable
PA package.
The MX-104 features four input channels, one program output, and one Foldback
output. The internal amplifier is rated at 100 watts into an 8 ohm load, and 150 watts
into 4 ohms.
Each input channel has an electronically balanced XLR connector, and a high-
impedance unbalanced 1/4" phone jack. In addition, each channel features two-band
EQ, a pre-EQ Foldback send, and post-EQ reverb send.
The master control section features a patchable 5-band graphic equalizer, a quality 3-
spring reverb, a full patch bay with 1/4" phone auxiliary and RCA tape inputs, and
master volume controls for Program, Foldback, and Reverb return to both. The power
amp protection circuitry and autocomp compressor, both with LED's, are also located
in this section.
Features
1. Four input channels
2. 100 watts into 8 ohms, 150 watts into 4 ohms
3. Patchable 5-band graphic EQ
4. Auto Comp compression unit w/LED
5. Built-in spring reverb
6. Power amp protection circuitry w/LED
7. Full patch bay
8. Aux input w/level control, RCA jacks and parallel phone 1/4" jacks.
9. Reverb level to PGM and FB
10. Independent Foldback mix.
Each Channel
1. Input level control
2. Two band EQ
3. Pre-EQ Foldback send
4. Post-EQ Reverb send
5. Low-Z electronically balanced XLR input
6. Hi-Z unbalanced 1/4" input
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— 2 —
Front Panel
Power Amp Compression
Indicator
(COMP)
Graphic Equalizer
(EQUALIZATION)
Reverb to Foldback
Control (REV TO FB)
This control adjusts the amount
of reverb signal that is returned
to the foldback buss and thus the
level of reverb contained in the
on-stage monitor mix.
High Equalizer Control
(HIGH)
The graphic equalizer is 5 inde-
pendent active bands (filters),
providing 12dB of boost or cut at
each center frequency. The "0"
detented position provides flat
audio response.
The Comp LED lights when the
internal compressor is activated.
The compressor is provided to
protect speaker systems by com-
pressing the input signal level of
the power amplifier when clip-
ping occurs in the output stage.
Frequent flashing of the LED is
not reason for alarm. However, a
constant or steady light indicates
that the MX-104 is being over-
driven and that the internal
power amplifier is possibly
"under powered" for that applica-
tion. The output level of the MX-
104 should be decreased until the
LED only flashes intermittently.
The high EQ control alters the
high frequency response of the
input channel, providing 13dB
at 10kHz, and 15dB at 20kHz of
continuously variable active
shelving equalization. The "0"
detented position provides flat
audio response.
Reverb/Control
(REV)
Foldback Master Control (FB)
The FB master control adjusts
the overall combined signal level
of the four independent channel
foldback sends, and thus the
level of the entire on-stage moni-
tor mix.
This control determines the
level of signal assigned to the re-
verb mixing buss. Rotating the
control clockwise increases the
amount of reverb in that channel.
Low Equalizer Control
(LOW)
The low EQ control provides
13dB at 100Hz and 15dB at
50Hz of continuously variable
active shelving equalization.
The "0" detented position pro-
vides flat audio response.
Foldback Control (FB)
The Foldback control deter-
mines the level of signal assign-
ed to the foldback mixing buss,
thus setting the level of that
channel in the on-stage monitor
mix.
Aux Level Control (AUX)
This control sets the overall level
of the Aux input signal.
Power Indicator LED
(POWER)
The indicator LED lights when
the power switch is "on".
Power Amp Protection
Indicator (PROTECT)
The indicator LED lights if the
power amplifier output is short-
ed, if the temperature of the unit
rises above acceptable levels, or
if DC is drifted to the speaker
outputs. If the LED should light,
speaker wiring and ambient
temperature of the MX-104
should be checked. If the LED
remains lighted, the unit should
be referred to qualified service
personnel for repair.
Reverb to Program Contro1
(REV TO PGM)
This control adjusts the amount
of reverb signal that is returned
to the program buss and thus the
level of reverb contained in the
main sound system.
Input Level Control
(LEVEL)
Program Output Jack
(PGM OUT)
The level control provides con-
tinuously variable adjustment
of the channel output to the
program mixing buss, thus
determining the level of that
channel in the main sound
system mix. Since the reverb
signal is "post" this control, an
increase in the level of the
channel's output will also result
The PGM Out jack is provided
for connection to external equal-
izers and/or power amps, deriv-
ing its signal prior to the internal
GEQ and power amp. Nominal
output level is +4dB with an
impedance of 600 ohms.
Program Master Control
(PGM)
The PGM control adjusts the
overall combined signal level of
the four independent channel
level controls, and thus the level
of the main sound system.
Note:
Graphic Equalizer Input Jack -
(GEQ IN)
The MX-104 protectioncircuitry
will (1) detect 'faulty conditions'
within the power amplifier, (2)
give a visual indication, and (3)
automatically shut down until
the fault condition is alleviated.
This special circuitry ensures
maximum reliability and vir-
tually eliminates equipment
damage due to unsafe or fault
conditions. Please refer to fault
protection table on page 4 for
full explanation of this im-
portant feature.
in
a
corresponding increase in
The GEQ input jack allows the
graphic equalizer to be used in-
dependently of the MX-104 with
other external equipment, or the
internal power amplifier and the
graphic equalizer with external
the reverb effect of that channel.
The nominal level of the input
level control is at the "10" posi-
tion.
Aux Input Jacks
(AUX IN)
The phone jack and RCA pin
jacks are wired in parallel, with
an input level of -20dB. When a
plug is inserted into the phone
jack, the RCA pin jacks are
automatically switched out of
the AUX circuitry.
High Impedance Connectors
(HIGH Z)
equipment. When
a
plug is
inserted, the main mix from
theprogram bussisdisconnected
from the graphic equalizer and
the power amplifier. The nomi-
nal input level is +4dB with an
input impedance of 50k ohms.
These connectors are unbal-
anced, standard 1/4" phone jacks
with an input impedance of 27k
ohms, and an input level of
-35dB. When a plug is inserted
into the high - Z input, the cor-
responding XLR connector is
automatically switched out of the
input circuitry.
Foldback Output Jack
(FB OUT)
Power Amplifier Input Jack
(PWR IN)
The PWR Amp input jack allows
the internal power amplifier to
be used with external equip-
Graphic Equalizer Output Jack
(GEQ OUT)
This jack is for connection to
external power amplifiers and/
or equalizers for the on-stage
monitoring system. Nominal
output level is +4dB with an
impedance of 600 ohms. If the
internal power amp and equal-
izer are to be used for the on-
stage monitor system, the FB
output should be connected to
the GEQ input jack.
This jack allows the MX-104
and the internal graphic equal-
izer to be used with an external
power amplifier, or in conjunc-
tion with the GEQ in jack, to be
used independently of all other
MX-104 circuitry. Nominal
o u t p u t level is +4dB with an
impedance of 600 ohms.
Low Impedance Connectors
(LOW Z)
The XLR connectors are low im-
pedance, electronically balanced
inputs with an input impedance
of 1k ohms.
ment. When
a
plug is inserted,
t h e power amp is automatically
disconnected from the MX-104
mixer section. The nominal in-
put level is +4dB with an input
impedance of 10k ohms.
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— 3 —
Rear Panel
Power Switch (POWER)
Cord Wrap
The power switch is
a
three-
The cord wrap is provided for
convenient storage of the power
cord when the MX-104 is not in
use.
position type with the middle
position being the "off position.
The MX-104 should be operated
in the switch position which
produces the lowest amount of
system hum.
Caution - The power cord should
always be completely removed
from the cord wrap prior to
operation of the unit. This will
insure maximum cooling of the
MX-104. For the same reason,
adequate clearance should be
maintained between the rear
panel and any other surface (4-6
inches should do). The vents on
the bottom and top of the MX-
104 are also provided for convec-
tion cooling. These vents should
be kept clear and open. Failure to
do so may cause thermal shut-
down of the unit.
Speaker Jacks (SPEAKERS)
The speaker outputs are stand-
ard 1/4" phone jacks wired in
parallel. Speaker cables (recom-
mend at least #18 gauge wire)
should be connected between
the MX-104 and the speaker
systems prior to applying power
to the unit.
Caution - The MX-104 should
never be operated into less than
a 4 ohm speaker load.
Earth Terminal (GND)
Warning
-
To avoid possible
equipment damage and/or per-
sonnel injury, the fuse should
always be replaced with same
type and rating. Using improper
fuses will also void the warran-
ty. The MX-104 should always
be disconnected from AC outlet
prior to changing fuses. If fuse
repeatedly fails, the unit should
be referred to qualified service
personnel for repair.
AC Power Cord
The power cord is the three-wire
type with proper grounding faci-
lities.
Caution - The ground pin should
not be removed under any cir-
cumstances. If the MX-104 must
be used without proper ground-
ing facilities, a suitable ground-
ing adapter should be utilized.
Operation of the MX-104 with
proper grounding techniques
will result in less system noise
and greatly reduced shock
hazard.
Fault Protection Table
Fault
Protection
Indication
Action
Restoration
Excessive current due to
overloads.
Current limiter activates at
less than 2 ohm.
Compressor
LED illuminates.
Remove excessive loads.
Minimum speaker loads
Automatic restoration
after normal loads are
obtained.
4
ohm.
Current limiter activates,
input signal is lowered,
unit shuts down,
Amp protection
LED illuminates.
Check speaker
lines/systems for shorts.
Turn off power switch.
Turn on into operational
loads.
Short circuits
(less than 0.4-ohm)
Temperature rise of heat
sink
Input signal is lowered.
Unit shuts down.
Amp protection
LED illuminates.
Check for adequate
ventilation.
Automatic restoration
after temperature
(more than 105°C)
lowers (to 75° - 95° C)
DC drift
Input signal is lowered.
Unit shuts down.
Amp protection
LED illuminates.
Refer to qualified service
personnel.
Automatic restoration
after normal bias is
regained.
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— 4 —
Connection Examples
SPEAKER SYSTEM
for foldback
(Self powered speakers
TOA model SM-25A)
MAIN SPEAKER SYSTEM
From Speaker jack
on Rear Panel
KEYBOARD
Low Z input should be connected
with low impedance (50 ohm ~ 600 ohm)
microphones
CASSETTE TAPE DECK
for playback
MUSICAL INSTRUMENT
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—
5
—
Input Connections
Generally speaking, there are two rules to follow when connecting equipment outputs
to the inputs of other equipment.
1. Properly match the impedances of the outputs and inputs.
2. Connect low impedance outputs to high impedance inputs.
It goes without saying that not only input and output impedance matching, but also
level matching should be taken into consideration. Each input channel of the MX-104
is provided with an Input Level Control that includes a negative feedback (NF)
circuitry, so the usable signal level range is wide. Input impedances and levels are
shown in the following table.
INPUT SPECIFICATIONS
SENSITIVITY*
(PGM OUTPUT
LEVEL +4dB)
ACTUAL
LOAD
IMPEDANCE
FOR USE
WITH
NOMINAL
CONNECTOR
CONNECTION
INPUT
-60dB (0.78mV)
-35dB (13.8mV)
XLR TYPE NC3F
PHONE JACK
CH1
CH4
LOW Z
OPEN
MICRO-
PHONES
HIGH Z
LOWER IMP
LINES
RCA PIN JACK
PHONE JACK
-20dB (77.5mV)
+4dB (1.23V)
+4dB (1.23V)
AUX
LOWER IMP,
LINES
PHONE JACK
PHONE JACK
GEQ
LOWER IMP,
LINES
PWR/AMP
LOWER IMP,
LINES
*Sensitivity is the level required to produce a program out level of +4dB.
*0dB is referenced to 0.775V RMS.
All XLR Type connectors are electronic balanced. Phone jack is unbalanced.
If the line going from one piece of equipment to another is long (more than 5m), we
recommend that balanced outputs be connected to balanced inputs.
As is described in the beginning of the Operating Instructions Manual, the connectors
of the MX-104 are wired as follows: Pin 1 is ground (shield). Pin 2 is cold (low, minus).
Pin 3 is hot (high, plus).
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— 6 —
Block and Level Diagrams
BLOCK DIAGRAMS
LEVEL DIAGRAM
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— 7 —
Specifications
MIXER SECTION
Frequency Response
Maximum Voltage Gain
INPUT to PGM out
INPUT to FB out
64dB
64dB
64dB
24dB
+0, -3dB 60Hz~20kHz (input LEVEL at "5" position)
INPUT to GEQ out
AUX to PGM out
Total Harmonic Distortion
0.05% +4dB* at 1kHz.
Input EQ
Hum and Noise (Open)
50Hz 15dB Shelving
20kHz 15dB Shelving
Equivalent Input Noise
Equivalent Input Noise
-130dB* (20Hz ~ 20kHz)
-133dB* (IHF A)
All level Controls Minimum
PGM Master at MAX and all
-110dB* (IHF A)
Equalization
input level controls minimum -90dB* (IHF A)
PGM Master at MAX and one
input level control at MAX -70dB* (IHF A)
63Hz 12dB Peaking
250kHz 12dB Peaking
1kHz 12dB Peaking
2kHz 12dB Peaking
8kHz 12dB Peaking
INPUT SPECIFICATIONS
SENSITIVITY*
(PGM OUTPUT
LEVEL +4dB)
ACTUAL
FOR USE
WITH
NOMINAL
CONNECTION
INPUT
LOAD
CONNECTOR
IMPEDANCE
-60dB(0.78mV)
-35dB(13.8mV)
XLR TYPE NC3F
PHONE JACK
CH1
CH4
LOW Z
OPEN
MICRO-
PHONES
HIGH Z
LOWER IMP
LINES
RCA PIN JACK
PHONE JACK
-20dB(77.5mV)
+4dB (1.23V)
+4dB (1.23V)
AUX
LOWER IMP,
LINES
PHONE JACK
PHONE JACK
GEQ
LOWER IMP,
LINES
LOWER IMP,
LINES
PWR/AMP
OUTPUT SPECIFICATIONS
OUTPUT LEVEL*
ACTUAL
FOR USE WITH
NOMINAL
CONNECTOR
CONNECTION
MAX. BEFORE
CLIP
SOURCE
NOMINAL
IMPEDANCE
+20dB (7.75V)
+20dB (7.75V)
+20dB (7.75V)
PHONE JACK
PHONE JACK
PHONE JACK
PGM
GEQ
FB
+4dB [1.23V]
+4dB (1.23V)
+4dB (1.23V)
POWER AMPLIFIER SECTION
Frequency Response
+0, -1dB 15Hz to 30kHz (150W RMS
Rated Power & Load
Input Sensitivity
+4dB* (1.23V)
Input Impedance
150W RMS
HOW RMS
Power Output at Clipping
Output Connector
Phone Jack x2
1% THD, 1kHz
160W RMS
Total Harmonic Distortion
Less than 0.1% (200mW ~ 150W RMS, 20Hz~20kHz, 4
Typically below 0.05%
Compresser Dynamic Range
Greater than 26dB
115W RMS
Power Requirement
294 W 120V AC 60Hz
Dimensions
494(W) X 184(H) X 304(D) (19.44 X 7.24 X 11.97) ins.
Weight
10 kg (22
l
b
s
)
Hum and Noise
At least 105dB S/N ratio, 20H/~20kHz
At least 109dB S/N ratio IHF-A weighted
Damping Factor
*0dB is referenced to 0.775V RMS.
*Specifications are subject to change without notice.
Greater than 200
— 8 —
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Characteristics Diagrams
LOW Z HIGH Z IN & INPUT EQ (LEVEL Control)
HIGH Z IN. & INPUT EQ (set at "5")
GEQ
POWER AMP POWER BAND WIDTH
POWER AMP T.H.D. vs POWER OUTPUT
POWER AMP COMPRESSOR
REVERBERATION FREQUENCY RESPONSE
Appearance
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— 9 —
TOA ELECTRIC CO., LTD.
KOBE, JAPAN
Printed in Japan
133-02-690-80
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