Yes, but it depends on the synth or MIDI keyboard in question, so not all of them will have the capability to turn off velocity sensitivity in controllers. Velocity is a MIDI effect that you can often place before your instrument in editing software. When turned on, it will intercept the MIDI from your keyboard and instead send whatever you set it at. Some devices, for example, allow you to adjust the velocity with various velocity number boxes. When you set these boxes to 0% velocity, the velocity will have no effect. You can also use a setting found on some synths and MIDIs that allow you to set the velocity model to "fixed," which locks in the velocity to a given level.