Here's a look at how the equalization controls on a tube amplifier work and sound. The basic controls on any amp are generally low, mid and high. The amp that I'm using to demonstrate those controls here has a couple of specialty equalization controls. The "Cut" knob is a special feature that allows further adjustment of the High frequencies. The "Boost" knob gives your tone an overall boost of certain frequecies. I use it when I'm needing that extra push in my tone.

Amplifiers can have any number of variations on tone knobs and features. An understanding of these basic features will help you be able to understand an variation on these features on any amp.