The freeDSP CLASSIC is a digital signal processor module based on the ADAU1701 and mainly THT components.
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The freeDSP CLASSIC is a cost-effective real-time audio signal processing solution for researchers and the do-it-yourself community. It is a bare circuit board that can be incorporated into your own projects. It comes with no housing. Easy assembling and simple programmability are the main focus. It is based on Analog Devices’ ADAU1701 DSP chip together with the free graphical development environment SigmaStudio. The programming model is function-block based – comparable to other graphical programming languages like PureData or Max/MSP. Many prebuilt blocks (e.g., filters, compressors, effects, or logic) can be placed in the signal path via drag and drop. If the included libraries do not have the functions needed, low-level blocks, such as multipliers and delays, can be wired together to create custom algorithms.

This board uses MAINLY THT components. The trickiest part is soldering the DSP, which comes in an SMD packaging. A complete SMD version is under development.


The freeDSP CLASSIC board offers two analog inputs and four analog outputs. Compared to other DSP solutions with easy programmability, the freeDSP and SigmaStudio offer a much wider range of DSP processing options and interface controls. It can be used in various audio applications, e.g.:

  • Room compensation / system equalization
  • Digital crossovers in active loudspeaker concepts
  • Multiband dynamics processing
  • Delay compensation / phase shift
  • Bass enhancement
  • Subwoofer integration
  • Advanced instrument audio effect units
  • Stereo image widening …

For more information, please refer to the website and the documentation.


This work and all other materials under are licensed under a Creative Commons Attribution Share-Alike 4.0 license. This allows for both personal and commercial derivative works, as long as they credit freeDSP and release their designs under the same license.