Changes

Most amps feature some form of EQ, with it more than likely acting on the signal after any pre-amp distortion. (The big exception is the Mesa/Boogie Mark series, which feature pre-distortion EQ knobs a post-distortion 5-band graphic EQ.) Modern amps commonly come equipped with Bass, Mids, Treble, and Presence controls, while older amps typically have a subset of those. Some amps simply have a Tone control, used to change the frequency emphasis from dark to bright. And some have a Mids control that actually sweeps the midrange center frequency, drastically altering how the other controls behave. Some amps' circuitry causes the EQ controls to "interact" with each other, meaning their behavior slightly changes depending on the settings of the other controls. It's always best to do a little research on the particular amp you are tweaking to understand these types of things before you end up tweaking in circles.

== External EQ's ==