Freeware - HoRNet Valvola VST Plugin

https://www.hornetplugins.com/plugins/hornet-valvola/

HoRNet Valvola (the Italian word for vacuum tube) it's an emulation of the electric behavior of a vacuum tube and its surrounding circuit. The sound of the plugin is as close as you can get to the real tube behavior since the code it's the direct modeling of the circuit characteristics obtained directly simulating the tube and the biasing circuit around it. The same technology is found inside our Guitar Kit plugin and Analog Stage plugin and we decided to give it away for free because we are proud of it.