Yes, you can certainly connect a turntable to any input on the amplifier, but if the amplifier does not have a built-in phono stage, you will need to use an external phono stage (such as the 551P or 651P) to connect in between the turntable to the amplifier. A phono stage boosts the low output from a turntable to 'line level' to allow connection to an amplifier.
The Topaz SR10 and AM10 amplifiers are the only Cambridge Audio amplifiers which have a built-in phono stage.
As the amplifier has no phono stage built in, it is not fitted with a turntable earth. Both the 551P and 651P phono stages have an earth for this reason. If you are using another manufacturers phono stage that is not fitted with an earth, you will need to consult with the turntable manufacturer for earthing options.