Thanks to F307 I found the way ; one has to open the amplifier and find the white switches on the phono board and set them at theposition for MC or MM , then one has to close the amplifier and connect the wire between phono and amplifier on the good entry.
With Onix , one has to change the phono board. With Cyrus one has not to open the amplifier and only connect at the right entry !! These British they like to have their own way !