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The ALF-PA2B is a compact-sized digital amplifier (Class-D) with 3 inputs (2 x lines in and 1 x balanced MIC). It is integrated with powerful functions, including bridge connection, dual-mono, EQ control, microphone mixer etc. It is a good application in different spaces, including classrooms, small meeting rooms, lecture halls, bars, pubs, etc.

Product Features

  • 2 x 20 Watt @ 4 ohm as the default amplifier output
  • Bridge connection function. Users can switch the ALF-PA2B to be 1 x 40 Watt @ 8 ohm by bridge connection
  • Two stereo audio inputs, switchable by panel button, IR remote and RS232
  • Volume / Bass / Treble controllable by panel buttons IR remote and RS232
  • MIC port can support balanced/unbalanced signal, suppresses the external noise effectively. Line audio output via 3.5mm jack, with controllable volume
  • Dual-mono up the stereo audio to two times mono audio. MIC mixer function
  • The microphone will be mixed to the line audio output, and be controlled separately
  • MIC input supports 48V phantom power, dynamic MIC, and Wireless MIC
  • Auto noise gate. Keeps detecting the audio and MIC input, will mute the output when there is no input
  • Ultra-low inrush current, no need for power sequencing, and this allows multiple PA2B to be powered on simultaneously without overloading power circuits
  • Convection cooled, a fan is not needed
  • Anti-static case design: providing good protection for long-term and stable performance


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 pluggable terminal block (3P,3.81mm), 


Output Connector 

1 3.5mm jack 

1 pluggable terminal block (4P, 5.08mm) 

Input Impedance  >10KΩ  Output Impedance  50Ω/stereo, 4~8Ω/Amplifier 
Audio General 
Frequency Response  20Hz ~ 20KHz  CMRR  >70dB@20Hz~20KH 


SNR  80dB at maximum output  Bandwidth  20Hz ~ 25KHz 
Stereo Channel 


>75dB@20Hz to 20KHz   

THD + Noise 



at nominal level 

Voltage Gain  32dB  Power Output  2×20 Watts (4 Ohms) 
Control Function 
RS232 Control  3-hole phoenix connector  Panel Control  Optional button control 
IR Remote  Optional IR remote 


1. Q – How many inputs does the PA2B support?

A –  3. 1 x RCA, 1 x 3.5mm jack and a microphone phoenix connector.

2. Q – Can I use this amplifier with a 100v system.

A – No, the amplifier is a low impedance amplifier.

3. Q – What is the output of the amplifier?

A – 2 x 20 watts @ 4 Ohm and 1 x 40 watts at 8 Ohm.

4. Q – How do I control the amplifier?

A – It is controllable via IR remote control and RS232.

5. Q – Am I able to loop this unit with another PA2B?

A – Yes, there is a loop out.