Hi Scott,
No I have not noticed any hum using this mixer with my Tyros. Then again I don't use it with speakers. I use the mixer to attach everything to and the route to the pc for recording.

I did initially think there was noise with the mixer but on investigation discovered I had messed up the settings on my Behringer Ultra Voice I put my mic through before sending the feed back to the Ty (so I can use the reverbs and VH) and then to the mixer. After I sorted that everything seemed fine.

I really can't recommend this little mixer highly enough for the money.

Best wishes
Tony