Hi!

If I remember correctly (and someone please correct me if I'm wrong, it's been a while), the A-190-3 is used to plug your A-100 into a computer, so the A-100's the slave/client/peripheral, and the computer's the master/server/thing in charge. So you can't hook the A-190-3 to a MIDI keyboard directly, you can hook up both that *and* a MIDI keyboard to some third device (such as a computer, and probably not much else). Then the keyboard will likely be drawing power from that device.

Hope that helps,
Zoë.