Mini Digital Amplifier, with MIC Mixer and EQ
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MMA220B
Mini Digital Amplifier, with EQ/Mixer
Index:
1. General Instruction ................................................................ 2
2. Product Picture....................................................................... 2
3. Features .................................................................................. 3
4. Specification .......................................................................... 4
5. Audio Connection .................................................................. 5
6. Buttons Controlling ............................................................... 8
7. RS232 Communication Protocol: ........................................ 10
8. System Diagram................................................................... 12
9. Panel Drawing ..................................................................... 13
USER MANUAL
Mini Digital Amplifier, with MIC Mixer and EQ
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1. General Instruction
MMA220B is a small digital amplifier (Class-D), with EQ control and MIC mixer
function. It is compact-size but powerful functions, including the bridge connection,
dual-mono, EQ control, microphone mixer etc.
It has a good application in different places, including classroom, small meeting room,
lecture hall, bar, pub etc.
2. Product Picture
Front Panel
Rear Panel
Top Panel
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3. Features
2x20Watt@4Ohm as the default amplifier output.
Bridge connection function. The user can switch the MMA220B to be 1x40Watt@8Ohm
by bridge connection.
Dual-mono function. The user can sum up the stereo audio to two times mono audio.
Microphone mixer function. The microphone will be mixed to the line audio
output, and separately controllable.
MIC input supports 48V phantom power, condenser microphone available.
MIC port with balance switching, can support balance/unbalance signal,
suppress the external noise effectively.
Auto noise gate. It keeps detecting the audio and MIC input, and muting the
output when there is no input coming.
Ultra low inrush current, no need for power sequencing. This allows multiple
MMA220B to be powered on simultaneously without overloading power circuits.
Convection cooled, fan is not needed.
Two stereo audio inputs, switchable by button, remote or RS232.
Fast switching speed. It is the high speed for the good performance.
Volume/Bass/Treble controllable by buttons or RS232
Line audio output, with volume controllable.
Antistatic case design: providing good protection for long-term and stable performance
LED indicator, for power and working status.
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4. Specification
Audio Input Audio Output
Input
2 stereo audio,
1 MIC
Output
1 amplifier,
1 stereo audio
Input Connector
2 RCA
1 3.5mm jack
1 captive screw connector,
Output Connector
1 captive screw connector
1 3.5mm jack
Input Impedance >10KΩ Output Impedance 50Ω/stereo, 4~8Ω/Amplifier
Audio General
Frequency
Response
20Hz ~ 20KHz CMRR >70dB@20Hz~20KHz
SNR 80dB at maximum output Bandwidth 20Hz ~ 25KHz
Stereo Channel
Separation
>75dB@20Hz to 20KHz THD + Noise
1%@1KHz, 0.3%@20KHz at
nominal level
Voltage Gain 32dB Power Output 2x20 Watts (4 Ohms)
Control Parts
Serial Control Port
RS-232, 9-pin female D
connector
Pin Configurations 2 = TX, 3 = RX, 5 = GND
NOTE: All nominal levels are at ±10%.
Mini Digital Amplifier, with MIC Mixer and EQ
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5. Audio Connection
5.1 Audio Output
5.1.1 Default output: 2x20Watt@4Ohm
The default output of amplifier is 2x20Watt@4Ohm. So, the user can connect the
amplifier output in the regular way. As the picture below:
5.1.2 Bridge connection: 1x40Watt@8Ohm
The MMA220B has the bridge connection, to double the output power at
1x40Watt@8Ohm. It will sum up the input left channel and input right channel to be
mono output, and the power is up to 40Watt.
The bridge connection is:
Switching to
the “STEREO”
Connecting the four pins, like this
Connecting the two pins, like this
Switching to
the “BRIDGE”
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5.1.3 Dual-mono output:
The MMA220B also has the function of double-mono output. It can sum up the left
and right channel, to be the mono audio output. In this way, the both of the outputs are
showing the same mono audio.
The connection is:
5.1 Microphone input
The microphone input of MMA220B has three different modes, and different modes
use different connections, as the picture below:
5.2.1 48V phantom power input
When the switch turns to “48V”, the microphone input will provide a 48V phantom
power. This is usually used for power supply for condenser microphone.
The connection is: “+” connects to anode, “-” connects to cathode and “╧” to ground.
NOTICE: In this mode, only condenser microphone can be connected with.
Connecting the four pins, like this
Switching to
the “MONO”
Input modes
switch.
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5.2.2 MIC input
When the switch turns to “MIC”, the microphone input is used for connecting with
dynamic microphone. There are two different connections:
1) Unbalanced connection:
a) “-” connects to signal, “+” and “╧” connect to ground.
b) “+” connects to signal, “-” and “╧” connect to ground.
2) Balanced connection: “+” connects to anode, “-” connects to cathode and “╧”
connects to ground.
5.2.3 LINE input
When the switch turns to “LINE”, the microphone input is used for connecting with
normal audio or wireless microphone output. There are two different connections:
1) Unbalanced connection:
a) “-” connects to signal, “+” and “” connect to ground.
b) “+” connects to signal, “-” and “” connect to ground.
2) Balanced connection: “+” connects to anode, “-” connects to cathode and “”
connects to ground.
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6. Buttons Controlling
The buttons provides the control of volume/EQ control and switching.
6.1 Audio switching
There are two switchable stereo audio inputs, one 2xRCA input, and one 3.5mm jack
input, switchable through the buttons as below:
Source
Selection
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6.2 Volume/EQ controlling
The line volume and Microphone volume can be controlled by the buttons.
The MIC Volume/LINE volume/LINE bass/LINE treble will be selected by the buttons,
and controlled up/down/mute by the function buttons. Please check the picture below:
For example, to turn up the line volume, you should select the “LINE” first, and then
press the button “ ”.
Select the function from
this menu in advance
Turn down/up the level.
Or mute the line volume
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7. RS232 Communication Protocol:
Baud rate: 9600 Data bit: 8 Stop bit: 1 Parity bit: none
Command Function Description Feedback Code
1A1. Switching the audio to input 1 A: 1 -> 1
2A1. Switching the audio to input 2 A: 2 -> 1
0A0. Mute Audio of MIC and Line out Mute Audio
1A0. Mute audio of MIC Mute MIC
2A0. Mute audio of line out Mute LIN
0A1. UnMute Audio UnMute Audio
600% Checking the working status
A: 1 -> 1
Volume: 30
Bass: 00
Treble: 00
601% MIC volume up Volume of MIC: 51
602% MIC volume down Volume of MIC: 51
603% Line volume up Volume of LINE: 51
604% Line volume down Volume of LINE: 51
605% Bass level up Bass of LINE: 04
606% Bass level down Bass of LINE: 04
607% Treble level up Treble of LINE: 04
608% Treble level down Treble of LINE: 04
609% Initialization, back to the default setting
A: 1 -> 1
Volume: 50
Bass: 04
Treble: 04
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Command Function Description Feedback Code
5[x][x]% Preset MIC volume, [xx] arranges from [00] to
[60].
61 degrees in total.
Volume of MIC: 50
7[x][x]% Preset line volume, [xx] arranges from [00] to
[60].
61 degrees in total.
Volume of LINE: 50
8[x][x]% Preset the bass level, [xx] arranges from [00]
to [08].
9 degrees in total.
Bass of LINE: 04
9[x][x]% Preset the treble level, [xx] arranges from [00]
to [08].
9 degrees in total.
Treble of LINE: 04
Notice:
1: The letter inside bracket [ ] is the variable code, which is the changeable.
2: The bracket [ ] is not included to the RS232 commands.
3: Any dot “.” after the letters is part of the commands.
Example 1
Switching the input 2 to the line out. We should send the RS232 command: [2A1.]
Example 2
Turning up the volume of line audio. We should send the RS232 command: [
603%
]
Example 3
Preset the MIC volume to be “21” degree. We should send the RS232 command:
[521%]
Example 4
Checking the working status of MMA220B. We should send the RS232 command:
[600%]
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8. System Diagram
2x20Watt@4Ohm
Looping connection
1x40Watt@8Ohm
Mini Digital Amplifier, with MIC Mixer and EQ
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9. Panel Drawing
Unit: mm
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