Whistle Rock Audio

ML2520 Discrete Opamp Kit


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The ML2520 is the result of many hours of critical listening tests and has been relentlessly refined throughout this process. It is Whistle Rock Audio's take on the famous AP2520 discrete opamp, popular amongst DIY enthusiasts and tweak-head audio engineers. It is a vital part of what makes the classic American console sound. The ML2520 will make your recordings shine with creamy highs, punchy mids and smooth bass.

To achieve the best possible 2520 layout, Whistle Rock Audio opted for a four-layer PCB design. The position and orientation of all components have been carefully optimized: The input transistors are protected against over-voltage and can easily be thermally coupled if desired. Finally, the output transistors have their respective biasing diodes next to them to allow for thermal coupling as well. The back of these transistors face outwards and are positioned along the edge of the PCB to easily mount heatsinks if required.


  • Improved 2520 circuit with input protection
  • Four-layer PCB design
  • Careful layout for maximum flexibility and easy assembly
  • Supply voltage: +/-12 to +/-18V
  • Quiescent current draw: +/-30mA @ +/-16V
  • Dimensions (LxW): 1.1"x1.1"
  • Height: 0.95" from the tip of pins to top of output transistors / 0.625 from lowest solder joint to top of output transistors
  • Standard 990 / 2520 footprint
  • High current output
  • Best quality components throughout

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