Faulty float valve

I have recently replaced the float valve in my tank for the hot water side of our system i installed a high pressure one as we have quite strong cold water pressure but when ever we run a bath the valve pulses as it refills rather than at a smooth constant fill rate ,i have tried closing the lever valve on the incoming main but this seems to exagerate the noise in the system,anybody have any suggestions as to cause.
Thanks
Mike.

When you replaced the float valve, was it nice and straight? Some times if tightened at a slight angle, this can cause vibration. Is pipe work clipped sufficiently where possible leading upto valve?

The pipework is as it was before i replaced the valve and it doesn't so much vibrate as make a woosh sound once every second as it fills.I will check to make sure it hasn't moved round as i have tightened the cooper nut.