Hornby do a class 66 sound decoder. Is your 66 DC ready ? If so pop the lid off, plug the decoder in off you go . If your 66 is not DCC ready then you will need to fit this yourself .pretty straight forward .the 66 tts is due in may The javelin as far as I know has no tts decoder available yet .you may need to source from an open model shop . Bear in mind a sound decoder also has a motor function and you might need two for the javelin to work the lights if so wish .this can be an ordinary decoder.