The Samson M25 Graphite worked for me only on my Mac Book Pro and not on Windows 8.1. After i had 2 hours trying everything possible and the MIDI keyboard while running Windows 8.1 in the Device list appeared but for example in Audition can not be used as an audio device is the Samson M25 Graphite back that I could buy at Amazon for a reduced price.
Other reports spoke of a wobble that I could not find in my unit.