Best Free Amp Simulator VST Traditionally used to emulate that vintage guitar sound that is unique to some old school amps, amp simulators can also be used with other instruments to achieve a unique sound. Below are our favorite free amp sim vsts. Blue Cat’s and Voxengo’s free amp simulators are some of the highlights. VST 4 FREE - Free Audio Plug-ins and Archives Free audio plugins archive - Instruments and effects for audio software. Plugins for Cubase, FL studio, Reaper, Ableton and other VST/AU platforms. Plugin guitar vst.