Mixing valve causing water flow issue

[uscpsycho]

I have a Kohler Laminar tub filler that fills my tub from the ceiling. Water has to travel a long way from the ceiling to the bottom of the tub and the flow without a mixing valve is perfect and doesn't splash. But when I put a mixing valve in at the water heater it does something to the hot water so that the flow out of the tub filler is choppy and splashes significantly.

I'm wondering if there is anything that can be done to prevent this effect?

I have tried two different valves by the same company with the same result. Perhaps a valve from another manufacturer will work better? Or is this always going to be the outcome with a mixing valve?