I just picked up a pair of MTX Thunder TA81001D amps, and according to the engineers at MTX there is no way to disable the subsonic filter or bypass the built in EQ in the pre-amp board (which is a crock). The TA92001, TE4001, and TE1501 units all have a button to bypass all of this garbage, but no such button exists on the TA81001. If you take the pre-amp board out, you can clearly see a spot on the board for the bypass switch - Labeled as "S102". MTX refuses to give me a schematic or instructions on what needs to be jumpered, removed, etc. to eliminate the EQ and Subsonic filter pieces. I'm about to tear into it myself, but figured I would ask here first. If anyone has experiencing modding these out, or access to to schematics for the TA92001, TE4001, or TE1501 pre-amp boards, It would be most appreciated.