“The Fireball II has two channels, overdrive and boost. Each channel has a separate gain button in order to set a different amount of overdrive on each channel. Use the overdrive channel to get a good crunch sound and
when you need extra punch for a solo you hit the boost button.”
pedal has a built-in compressor and you can choose between medium and high compression or no
compression at all. The compressor at medium level smooths out the
notes while retaining the dynamics of the notes you play. The end result is the sort of sound you get from a really good preamp,
overdriven and played through a whole stack of effects.”
More information on a newer version of this effect can be found here.