I have a volume control knob for my bass amp, do I need the Epicenter remote knob?

Yes. On the surface, it seems like a volume knob, since when you turn the knob up, the volume increases, but it is NOT a volume knob.

If you do not have the Epicenter knob connected, the Epicenter effect is off. Effectively putting the Epicenter in to bypass mode.

The Epicenter remote knob controls the amount of Epicenter effect that is added to the existing signal.

The more you turn it up, the more bass frequencies are added to your audio signal. If you turn it all the way down, it is adding almost no additional bass frequencies to the audio signal.