Numark Power Supply 6V DC 1A

I got this because my AKAI MPK25 doesn't send MIDI over MIDI out if it's powered over the USB cable.
I wasn't quite sure this is the case because the user manual of the MPK25 doesn't tell you this. Other AKAI controllers do this also so I was hoping mine was the same.

And it works!
My MPK25 now sends MIDI signal over 5pin MIDI out. I now use the MPK25 to control the Korg NTS-1 or Korg Volca Bass.

The power adapter looks simple. The cable is long so this is great.
It is expensive but well made power supplies are expensive - believe me I opened a couple of them and better power supplies have copper plated shielding and some other stuff that makes it a better option in the long run.