RDL FP-PA20A 20 W Mono Audio Amplifier - 70 V or 100 V

The FP-PA20A 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. Both a 70 V and 100 V amplified output are 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-PA20A produces average audio levels and audio clarity normally expected of amplifiers delivering much higher output power.


  • 20 Watts RMS Constant Voltage Amplifier
  • 70 V and 100 V Outputs
  • Integral Audio Compressor to Control Clipping
  • High Overall Operating Audio Level
  • Maximized Audio Level for Output Power
  • Audio Quality Superior to Standard Amplifiers
  • Plenum Rated per UL 2043 Standard

Input / Output Connector:

Detachable terminal block


Line level (+4 dBu bal; -10 dBV unbal)

Input Impedance:

20 kΩ balanced bridging; 10 kΩ unbalanced

Gain Adjustment:

Single turn audio taper

Minimum Input Levels:

Balanced: -26 dBu (to cross compressor threshold)
Unbalanced: -28 dBV (to cross compressor threshold)

Maximum Input Levels:

Balanced: +23 dBu
Unbalanced: +15 dBV

Frequency Response:

50 Hz to 20 kHz (± 3 dB)*


< 0.1% (@ 1 kHz)*
< 0.5% (50 Hz to 20 kHz)*
*measured at compressor threshold level equaling 4 W RMS output power

Plenum Rating Standard:

UL 2043

Overall Dimensions:

Height: 2.3 in. (5.85 cm); Width: 3.25 in. (8.26 cm); Length: 6 in. (15.3 cm)


< -80 dB (below 20 W RMS)


Threshold 6 dB below rated output, automatic adjusting attack and release


> 55 dB (50 Hz to 120 Hz)

Output Power:

20 W RMS @ 70 V or 100 V

Ambient Operating Environment:

0° C to 30° C Max; 20° C Recommended

Indicators (2):

Red LED: PEAK LED indicates compressor activity
Green LED: Power ON

Power Requirement:

24 Vdc @ 1650 mA, Ground referenced (for continuous RMS power output) 24 Vdc @ 1000 mA, Ground referenced (for normal uncompressed audio)