BDI21 - analyzing the EQ curve and a minor mod | TalkBass.com
Trimmed down pedalboard set up : r/basspedals
Presence gain on BDI21
Modified Behringer V-Tone BDI21 | eBay
Current Bass Pedal Board, able to get some seriously heavy sounds out of a couple of sub £100 pedals. Signal chain and discussion in comments. : r/guitarpedals
Behringer BDI21 Manual : Behringer : Free Download, Borrow, and Streaming : Internet Archive