A (simple) MIDI-I/O Adapter for connecting to a Hughes & Kettner GrandMeister (or TubeMeister) guitar amp (with phantom powering)
This is a simple MIDI I/O for Arduino. Also there is a conection to a TM138 button/LED circuit for changing programs or state of the amp via MIDI.
It uses a DC/DC step-down LM2596 for phantom powering the circuit from the H&K MIDI adapter. This is a 7 pin DIN plug where pin 6 and 7 will be used for powering (max 150 mA!).
NO WARRANTY for using this circuit!