The GAIN control adjusts the preamp instrument level and also the amount of overdrive. When the Clean Channel is selected, low to medium settings will deliver a clean sound and as the Gain is increased the sound will gradually become more overdriven. When the Overdrive channel is selected (OD switch) there will be moderate overdrive at all Gain settings, which again increases as the control is turned clockwise.
The EQ control allows you to adjust the depth of the EQ curve for preferred tonal response, from relatively flat with a slight mid-range boost, through to a formed mid response with a cut at around 400Hz. The depth of mid-range cut is continuously variable between the two extremes. You will find that the combination of the two channels and the carefully voiced EQ result in a huge range of great bass tones.
COMPRESSION is used to subtly smooth out the dynamic range of an audio signal, therefore softening the peaks and attack, as well as boosting the volume of lower levels which then increases sustain. The compression ratio of the in-built compressor is variable so you can dial in exactly the response you want.
The SUB control sets the level of a harmonic generator. This produces an additional low frequency tone that is mixed in with the normal signal. It gives the perception of increased low-end girth and incredible bass from a mini amp.
The VOLUME control adjusts the overall volume of the amplifier, turning it clockwise will increase the level.