perhaps /pərˈhæps/ /pəˈhæps/
rather /ˈræð.ər/ /ˈrɑːðə/
on the contrary /ɑn ðə ˈkɑntrɛri/ /ɒn ðə ˈkɒntrəri/
but /bʌt/ /bʌt/