MDA, short for Maxim Digital Audio, is a collection of free audio plug-ins originally developed by British software engineer Paul Kellett beginning in the late 1990s. The set is best known for being among the earliest widely circulated VST plug-ins, and for combining low CPU usage with sound quality that made it a fixture in home studios during the formative years of computer-based music production. Distributed for years as freeware from the mda-vst.com / mda.smartelectronix.com domain, the source code was eventually released under MIT and GNU licenses, and the plug-ins have since been ported to AU, LV2, and modern VST3 formats by community maintainers.

The collection contains roughly three dozen processors, the bulk of which are effects: dynamics tools such as Limiter, Combo, Multiband, Dynamics, and Bandisto; modulation and stereo utilities including Detune, Stereo, Tracker, RingMod, and Leslie; reverbs and delays such as Ambience, DubDelay, and Delay; and a wide assortment of filters, distortions, and de-essers. Four instruments round out the bundle: the Piano (acoustic), ePiano (a Rhodes-style electric piano based on sampled material), JX10 (a two-oscillator subtractive synth), and DX10 (a simple FM synthesizer). The Piano and ePiano in particular became go-to default sounds in countless DAW templates due to their light footprint and serviceable tone.

Because the plug-ins are open-source, they are now bundled or repackaged inside numerous host applications and distributions, including PlugInGuru's Unify, the Elk Audio platform, and various Linux audio packages. Reimplementations using the JUCE framework, as well as LV2 builds maintained by David Robillard, keep the code running on contemporary systems, ensuring that the original mda designs remain in active use far beyond their original closed-source freeware era.

MDA has 7 products cataloged on Equipboard, including Synth Plugins, Virtual Instrument, and Delay Plugins. Their gear is featured by 4 artists, with the strongest followings in Electronic and Pop. Notable users include Madeon, Mat Zo, and Laidback Luke.