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Connector Type
Push Terminal
LED Feedback
Maximum Power Handling
20 Watts
Ease of Installation
Beginner (Installs < 10 minutes)
Radio Design Labs
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Powerful, Reliable Amplifier with Internal Compressor
Radio Design Labs FP-PA20B 20W Mono Audio Amp, 25V
Radio Design Labs FP-PA20B 20W Mono Audio Amp, 25V
Radio Design Labs FP-PA20B 20W Mono Audio Amp, 25V
Item# 77991
Price: Normally $186.99 
Hot Deal $122.97
Free shipping on orders over $175 - See Details


  • 20 Watts RMS constant voltage amplifier
  • 25V output
  • Integral audio compressor to control clipping
  • High overall operating audio level
  • Maximized audio level for output power
  • Audio quality superior to standard amplifiers

Essential Info

The FP-PA20B features a balanced line level input that may be connected unbalanced. A front panel gain control is designed to be adjusted either manually or with a trimming screwdriver. The gain range will accommodate standard unbalanced levels as well as professional balanced levels. A 25 V amplified output is provided to drive corresponding speakers in a distributed sound system. Audio levels that could cause the amplified output to clip are compressed using two dynamic time constants designed to preserve aural transparency. Normal audio level signals remain unaffected by the compressor thereby preserving audio dynamics and preventing the compressor from increasing feedback potential when the amplifier is used for paging. The FP-PA20B produces average audio levels and audio clarity normally expected of amplifiers delivering much higher output power.

Also available in 8 Ohm and 70V/100V versions.

This item requires a 24V power supply such as the PS-24AS or PS-24K for operation.


More Info

  • Input / Output Terminal Block Connections
  • Line Level Balanced or Unbalanced Input
  • Integral Audio Compressor to Control Clipping
  • High Overall Operating Audio Level
  • Peak LED to Indicate Audio Compression
  • Ultra-compact All Metal Construction
  • Convenience of RDL FLAT-PAKs
  • Specifications

    • Input: Line level (+4 dBu nominal balanced, -10 dBV nominal unbalanced)
    • Input Impedance: 20k Ohms balanced bridging, 10k Ohms unbalanced
    • Input / Output Connectors: Plug-in terminal block
    • Gain Adjustment: Single turn audio taper
    • Minimum Input Levels, Balanced: -26 dBu (to cross compressor threshold)
    • Minimum Input Levels, Unbalanced: -28 dBV (to cross compressor threshold)
    • Maximum Input Levels: Balanced: +23 dBu, Unbalanced: +15 dBV
    • Frequency Response: 50 Hz to 18 kHz (+/- 3 dB)*
    • THD+N: < 0.1% (@ 1 kHz)*, < 0.5% (50 Hz to 20 kHz)*
    • Compressor: Threshold 6 dB below rated output, automatic adjusting attack and release
    • Noise: <-80 dB (below 20 W RMS)
    • CMRR: > 55 dB (50 Hz to 120 Hz)
    • Output Power: 20 W RMS @ 25 V
    • Ambient Operating Environment: 0° C to 30° C Maximum; 20° C Recommended
    • Power Requirement: 24 Vdc @ 1650 mA (for continuous RMS power output, Ground referenced) 24 to 33 Vdc @ 1000 mA (for normal program material with minimal compression, Ground referenced)
    • Indicators (2): Red LED: PEAK LED indicates compressor activity, Green LED: Power ON
      *measured at compressor threshold level equaling 4 W RMS output power


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