40 W Stereo Audio Amplifier - 8 Ω, with Power Supply

  • Stereo Audio Power Amplifier
  • 20 Watts RMS per Channel into 8 Ω – 40 Watts Total
  • 15 Watts RMS per Channel into 4 Ω – 30 Watts Total
  • Left and Right Unbalanced Phono Jack Inputs
  • Switch-Selectable Stereo or Mono Operation
  • Studio Quality, Aurally Transparent Compressor/Limiter
  • Compressor/Limiter Controls Clipping
  • Compressor Produces Maximized Average Output Power
  • Compression Enabled Using Input Level Adjustments
  • LED to Indicate Audio Compression Threshold
  • Outputs Drive 4 or 8 Ohm Speakers
  • High-Efficiency Class D Operation
  • Thermal and Short-Circuit Protection
  • TX-PA40D includes North American Cord; TX-PA40DE excludes Power Cord
Recommended Power Supply ( Included )
() ()


The TX-PA40D is the ideal choice in many applications where a high quality, high-efficiency utility amplifier is needed to drive a pair of 4 Ω or 8 Ω speakers. It is specifically suited to fixed-gain amplification applications where gain is controlled by other equipment. Examples include projectors with variable audio outputs used in classrooms, boardrooms and video conferencing.

The TX-PA40D features two unbalanced line level inputs on high-reliability gold plated phono (RCA) jacks. A front-panel recessed gain control trimmer permits setting the desired amplifier output level for each channel. The gain range accommodates the range of typical unbalanced audio signal levels. Each of the two TX-PA40D outputs will drive a 4 Ω or 8 Ω speaker or multiple speakers connected to present a 4 Ω or 8 Ω load to the amplifier. The output impedance is switch-selectable on the front panel of the module.

A front-panel switch is provided to sum the audio inputs to mono. In the STEREO mode, the TX-PA40D independently amplifies each audio channel, left (L) and right (R). If speaker placement in the specified installation is incompatible with stereophonic amplification, the INPUT MODE switch may be set to SUMMED MONO.

The TX-PA40D includes a stereo analog compressor/limiter for audio fidelity noticeably superior to conventional class D amplifiers with digital limiting. The input GAIN settings determine whether the limiter alone is used for clipping suppression, or if the full compressor/limiter will be used to substantially increase the average output power beyond that of a standard 40 W amplifier. A red front-panel LED flashes when the limiter is preventing output clipping. Normal audio level signals remain unaffected by the compressor thereby preserving audio dynamics. If the input level is increased so the compressor is active, the LED remains dimly lit between peak flashes. The audio is compressed according to three dynamic time constants providing aural transparency while maintaining clean, unclipped amplified audio for input overloads of up to 20 dB. The TX-PA40D, with compression, is capable of producing average audio output levels and clarity normally expected from stereo amplifiers with a much higher output power rating.

A blue POWER LED illuminates when the TX-PA40D is powered from its external 24 Vdc power supply. The module is equipped with both thermal and output short-circuit protection. The high-efficiency Class D output stages produce minimal heat for all levels of expected voice or music modulation. Continuous full-power operation with audio tones will not damage the amplifier, but is not recommended.

Wherever an ultra-compact, high quality, high efficiency audio power amplifier is needed to provide reliability and unsurpassed versatility, the TX-PA40D is the ideal choice. Use the TX-PA40D individually, or combine it with other RDL products as part of a complete audio/video system.


Inputs (2):Line level (-10 dBV nominal unbalanced), Left and Right
Input Impedance:10 kΩ unbalanced
Gain Adjustments (2):Single turn, one per channel
Minimum Input Levels:-18 dBV (to cross compressor threshold)
Maximum Input Levels:+15 dBV
Frequency Response:20 Hz to 20 kHz (± 1 dB, 4 or 8 Ohms)*
THD+N:< 0.1% (1 kHz, 1 W, 4 or 8 Ohms); < 1% (50 Hz to 20 kHz, 8 Ohms)*
*measured at compressor threshold level equaling 12 W RMS (8 Ohms) output power
Compressor:Threshold nominally 2 dB below rated output, automatically adjusting attack and release times
Crosstalk:Better than 60 dB (1 kHz, no compression)
Noise:< -75 dB (below 20 W RMS)
Selectors:Slide switches: Output Impedance 4 Ohms or 8 Ohms; Input Mode SUMMED MONO or STEREO
Output Power:20 W RMS into 8 Ω per channel, 40 W RMS total; 15 W RMS into 4 Ω per channel, 30 W RMS total
Output Circuit:Class D
Ambient Operating Environment:0° C to 40° C Maximum; 20° C Recommended
Indicators (2):Red LED: THRESHOLD LED indicates compressor activity
Blue LED: POWER on
Power Requirement (Supply Included):Input: 100 to 240 VAC, 50 to 60 Hz, 1.5 A, IEC C14; Output to module: 24 Vdc
Package Type:Cardboard Box
Tariff code:8543.70.9910
WEEE weight:1.525 lbs.
Shipping Weight:1.655 lbs.
Package Dimensions:5.125 x 2.5 x 5.875 in.
Dimensions:3.17" (8.05 cm) W; 1.76" (4.47 cm) H; 2.06" (5.23 cm) D 3.17 x 1.76 x 2.06 in

Related Products

Power Amplifiers
  • EZ-MXA20

    20 W Stereo Audio Mixer-Amplifier with EQ - 8 Ω, with Power Supply

  • EZ-PA20

    20 W Stereo Audio Amplifier - 8 Ω, with Power Supply

  • RU-PA40D

    40 W Stereo Audio Amplifier with VCA - 8 Ω, with Power Supply

  • RU-PA518

    10 W Stereo / 18 W Mono Audio Amplifier - 8 Ω

  • Mono 18W Amplifier


    18 W Mono Audio Amplifier - 8 Ω

  • ST-PA2

    2 W Mono Audio Amplifier - 8 Ω

  • Compact Audio Amplifier


    6 W Mono Audio Amplifier - 8 Ω

  • FP-PA20

    20 W Mono Audio Amplifier - 8 Ω

Pole Mounting Accessories

Related Products

General Mounting Accessories
  • MB-1

    Mounting Kit - RU, ST and TX Series

  • MB-2

    Mounting Kit - RU and TX Series

  • MB-3

    Kit to Mount ST, TX Series Modules on FP Panel

  • SR-4

    STICK-ON Series Mounting Rack - 7 modules

TX™ Mounting Accessories
  • TX-HRA3

    10.4" Rack Mount for 3 TX Series Products

  • TX-RA5

    TX Series 19" Racking System - 5 modules 1RU

  • TX-RRB1

    Rear rack rail mounting kit for any TX series module

  • RC-HPS1

    10.4" Rack Mount for Desktop Power Supply and TX Module

Pole Mounting Accessories
DIN Rail Mounting Accessories




CAD FilesUnitsFormat
Engineering Functional BlockAmericanDXF
Panel Diagram - FrontAmericanDXF
Panel Diagram - RearAmericanDXF
Panel Diagram - FrontMetricDXF
Panel Diagram - RearMetricDXF
High Res ImagesFormat
Declaration of Conformity


How To Buy

Direct Dealer Program

Becoming an RDL direct dealer is quick and easy. To become a direct dealer, your company must meet the following requirements:

  • Must be an A/V contractor, sound contractor or system integrator
  • Must po