Small mono amp is surprisingly powerful for its size, and efficient - able to deliver up to 2.5 Watts into 4-8 ohm impedance speakers. 

Features 

• Volume trim pot so you can set/adjust the amount of amplification on the board.  This is a generic board - every install varies.  There are 6 connections:
  
• Positive and negative speaker in
• Positive and negative speaker out
• Positive voltage connection.  You will need to probe for a switched voltage source (only on when power switch on).
• Negative power connection
• Note: the hole labeled "SD" is not used.
• Output Power: 2.5W at 4Ω, 10% THD, 1.5W at 8Ω, 10% THD, with 5.5V Supply
  * 50dB PSRR at 1KHz
  * Filterless design, with ferrite bead + capacitors on output.
  * Fixed 24dB gain, onboard trim potentiometer for adjusting input volume.
  * Thermal and short-circuit/over-current protection
  * Low current draw: 4mA quiescent and 1uA in shutdown mode