I just plugged my Roland A-49 to my MacBook Pro (Early 2011 2.3 GHz). The MIDI keyboard would have its power supplied via USB, but it has no power. The specification says it needs 98 mA current, which is way less than the 500 mA provided by the MBP's USB 2.0 port. If I plug it into a desktop PC, it works. What can be the problem? An USB hub would solve this issue, I suppose, but can I avoid buying one?

  • Is it same on all USB ports?
    – Ruskes
    Commented May 6, 2013 at 13:49
  • Yes, I tried all of them. With other devices (iPad, pendrive) they work properly.
    – thSoft
    Commented May 6, 2013 at 13:59
  • Start the Garageband and check under preferences- audio if it has detected your midi device.
    – Ruskes
    Commented May 6, 2013 at 14:10
  • Did you check they web site for downloads ?
    – Ruskes
    Commented May 6, 2013 at 14:26

4 Answers 4


I do not think it is a power problem.

Check in GarageBand if your device is showing up.

If not: I would start with getting the latest software for your MIDI device

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  • And you were right, after installing the latest driver, it works! I couldn't imagine that the powered state of the hardware depends on a driver software...
    – thSoft
    Commented May 7, 2013 at 7:42
  • 1
    You are welcome. Just to clarify, YES! the system has to recognize who is knocking at the door (the right driver) before giving it "permission" to enter. ;)
    – Ruskes
    Commented May 7, 2013 at 7:54

http://forums.rolandclan.com/viewtopic.php?f=54&t=45738 On my A49 you have to hold down the "Function" "Pitch" and "Assign" buttons on the keyboard all at the same time as you power it on.


You will need to disenable the SIP control of the Mac OS. Here a link that tells you how to do that; http://osxdaily.com/2015/10/05/disable-rootless-system-integrity-protection-mac-os-x/

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    – fsb
    Commented Nov 27, 2016 at 15:27

Have you Check the Cable? Most thats Simple is it or the Plug not Right in there.

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