Flextron is a free virtual-analog guitar amp VST. It’s based on a concept of the hybrid guitar distortion pedal. The prototype pedal in its turn was based on two commercial tube emulation technologies.
Tube Amp Ultra 530 is a free VST / AU plug-in (briefly U530) for PC/Mac based on the popular sound studio preamp ENGL® E530, having a wide range of tone. On this basis, you can customize the sound of the powerful hi-gain to bright crunch and crystal clean tone.
TPA-1 is a digital emulation of a class AB tube power amplifier VST/AU plugin effect for guitar.
X-Tube is a free VST plugin that simulates tube amplifier saturation effect.
The Anvil is a digital emulation of a three channels free vst tube preamplifier plugin for guitar.
Studio Devil British Valve Custom is a FREE guitar amp modeling and audio effects plug-in for use with VST, AudioUnits, and ProTools RTAS compatible hosts running on both Mac and Windows platforms.