Some audio stomp boxes use a 9V battery tray that makes it tricky to adapt to wall power. The LR Baggs Para Acoustic DI uses the battery tray and doesn't have the typical 5.5mmx2.1mm power plug.
I considered hacking in the power connector, but decided instead to 3D print an adapter with the same dimensions as the battery tray so I can use the pedal with wall power and without modifying the pedal.
Source files included for FreeCad (0.16).
the little wedge on the bottom keeps the tray from sliding out.. this is somewhat optional (mine was a pretty snug fit without it) and you might have to tweak your printer parameters a bit to get this to work. Mind the direction of the wedge, the point is to keep the tray in.
The power jack is a Radio Shack 2741563 but any similar 5.5 x 2.1mm coaxial power jack should work (7/16" hole). Good luck finding a Radio Shack, nowadays.
I had to enlarge the wire holes slightly. Light gauge solid wire is probably easiest to work with (20 or 22 ga). I used stranded wire, but pre-soldered it.
- Be aware of the polarity of your device! Most 9V stomp boxes use a center-negative power connector (Thanks, Boss/Roland). Getting the polarity wrong could toast your precious pedal. Use a volt-meter and check the polarity while connected to the power adapter before powering up the pedal!
The high part of the wedge is near the little handle/front of the tray
Soldering required. Note: negative on the left, positive on the right terminal in this pic.
If you're soldering-challenged then you might redesign the part to work with one of these screw-terminal adapters.