"FULLNESS TUBE EQUALIZER"
2 Band Tube Equalizer.
HIGH: Determines the high frequency & Saturator.
HIGH GAIN: Boosting high frequency level.
BASS: Determines the low frequency.
BASS GAIN: Boosting low frequency level.
DRIVER: The driver is adding a very subtle and pleasing harmonic distortion to the signal. This ends up boosting the harmonics above the normal range you expect to hear which creates a sense of fullness. When an entire song has each track featuring this warmth, you get an extremely full sound: