Feedback Bass
Create the feedback loop:
1: Mixer to VCA-B/LPF in.
2: LPF to Mixer In-2.
The LPF will attenuate and boost certain frequencies. Find what sounds right. Find the right balance between the LPF and mixer levels.
Try:
1: Patching from the mixer directly back into Mixer In-2.
2: Patching from VCF or Main to the LPF.