Gain 2 is a second Gain knob used with some amp models that determines the amount of overdrive in the pre-amp stage. Gain 2 (also known as “Presence” on some amps) allows for more harmonic subtleties in character of the amp tone. The default is 5.0. Gain 2 range is from 0 to 10.The Gain 2 control on the Tweed Lux, AC Hi Boost and Plexiglass is in parallel (“jumped”) with the Gain 1 control. The M-2 Lead is in series, meaning the signal goes in and out of Gain 1, then into Gain 2.Tone controls let you shape the highs, mids and lows of the amp sound. Electric guitar pickups tend to have a strong low-mid emphasis and little high frequency response, often producing a mid-range heavy sound that requires some treble boost. The response and interaction of the tone controls are unique to each amp.The Bass control determines the amount of low end in the amp tone. The response of this control in some models is linked to the setting of the Treble control. The default setting is 5.0. Bass range is from 0 to 10.The Middle control determines the mid-range strength in lower gain sounds. With high gain amp models, the Middle control has a more dramatic effect and can noticeably shape the sound of the amp at both the minimum and extreme settings. The default setting is 5.0. The Middle range is from 0 to 10.In most amp models, the Treble control is the strongest of the three tone controls. Its setting determines the blend and strength of the Bass and Middle controls. When Treble is set to higher values, it becomes the dominant tone control, minimizing the effect of Bass and Middle controls. When Treble is set to lower values, the Bass and Middle have more effect, making for a darker amp tone. The default setting is 5.0. The Treble range is from 0 to 10.