Syntler has announced the release of Bonch-Bruevich Tube 1.5, a free tube exciter VST effect plugin for Windows.
You can use Bonch-Bruevich Tube to add higher harmonics to the incoming signal. The author promises that this effect plugin will make your sound more detailed, being good for guitars, vocals and synths.
I tested the plugin on a synth and some loops, and indeed it brightens and warms the sound; with Harm knobs at high values, Bonch-Bruevich Tube adds grit and some distortion. It is a little and simple plugin, good to color and enhance plain sounds.
Bonch-Bruevich Tube is available as a VST plugin (32-bit only) for Windows. The download size is 2.1MB compressed.