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K5181 • Classic 250W Class D Audio Amplifier Kit


Cat. Page 221

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  • $89.95
  • 4+ $80.95
  • Price per each
  • Includes GST


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Last updated 15-08-18 08:21:15

This product has been viewed 1545 times.

  • Accessories
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Loudspeaker Protector Kit to suit K5181


  • $29.95
  • 4+ $26.95
  • Price per each
  • Overview
  • Specifications


(Silicon Chip Magazine Nov 12) This high specced power amplifier operates in Class 'D' as opposed to earlier amplifiers which run in the more conventional Class 'AB' or Class 'A'. The new Class 'D' amplifier offers the extremely low distortion figures of a Class 'A' whilst still having the efficiency of a standard class'AB' amplifier. This simple to build kit with its 250W into 4Ω output will make an ideal subwoofer or front floorstanding speaker driver in a home cinema setup.

Important Note For Kit Buyers:
This product is supplied in component form and requires soldering, drilling, and assembly. We recommend users are familiar with at least basic electronic principles and have the ability to solder.


  • High efficiency
  • high power
  • Low distortion and noise
  • Bridging option for driving 8Ω loads with two modules
  • Over-current protection
  • Over-temperature protection
  • Under-voltage switch-off
  • Over-voltage switch-off
  • DC offset protection
  • Fault indicator
  • Amplifier running indicator
  • Optional speaker protector module

Why buy an Altronics Kit?
Altronics kits are premium do-it-yourself projects designed to be assembled with ease. However, basic electronics knowledge and soldering skills are essential to construct our kits. A difficulty rating is provided to help determine if your ability is sufficient to build the kit project. Please note, once assembly has been commenced we are unable to honor any warranty claims. Please see the full details here.


  • Total harmonic distortion and noise: Typically <0.01%
  • Power output: Up to 150W into 8Ω and 250W into 4Ω power supply dependent
  • Power output, bridged, 8Ω only: 450-500W power supply dependent
  • Efficiency: Typically 90% at full power for 8Ω and 83% for 4Ω
  • Signal-to-noise ratio: 103dB with respect to full power
  • Input sensitivity: 2V RMS@4Ω, 2.2V RMS@8Ω
  • Frequency response: 10Hz - 20kHz +/-1dB
  • Power requirements: +/-40 - 60Vdc, 50-55V nominal
  • Over-temperature cut-out: 75C
  • Under-voltage threshold: +40V
  • Over-voltage threshold: +75V
  • DC offset protection threshold: > +/-4Vdc
  • Over-current threshold: 29A
  • Idling (no signal) frequency: 500kHz adjustable
  • MOSFET dead time: 45ns

*Specifications are subject to change without notice.

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  • Hi there, What is the power supply required for this unit? Cheers Global PC
    Global PC

    Power supply, transformer, rectifier etc are not included. However the kit instructions (page 14) do give some extra detail on suitable parts to buy. For example, the K 5168 power supply kit is suitable for use as a power supply, along with a 35-0-35 transformer (such as M 5535) and a bridge rectifier (Z 0091.)


  • Would I be able to connect the K5340 • Guitar Preamp Kit to this amplifier? If yes, would this be difficult to do? If no, which amplifier would be the best choice for the guitar preamp?

    Although it hasn't been tested here, the K5340 should be ok to connect to the K5181, and it should be relatively straightforward. Do note however that both the K5340 and K5181 are modules only, so you will need to give consideration to the power supply used and extra modules required. Firstly the transformer - Altronics do stock some transformers with auxiliary windings (eg MC5535) which would have 35-0-35V windings suitable for the 5181 and 15-0-15V windings suitable for the preamp. Although the 5340 has on-board rectifier and regulator sections, the 5181 would require a power supply module (eg K 5168) and a bridge rectifier (eg Z 0091) For more technical details regarding the two kits you may also like to contact Silicon Chip (silchip@siliconchip.com.au) Regards, Kits


  • Hi, Does the amp module include the full instructions or do we need to source them seperately from SC?

    Hello, The amp module includes the full instructions as published in November and December 2012 - except for assembly instructions for the speaker protector module (which we sell as K 5182 - it has its own set of instructions.) Hope that helps.