Yes, another daft LED question. Sorry.
I have a set of small LED Christmas lights, to decorate a miniature tree. Power is from 2 AA batteries. Were I to have four identical sets, could I wire them in series and run using a 12v transformer? I am thinking of an old (1960s) toy train transformer which provides 0-12v DC. My first thought is 'yes, of course', but realise that not all power sources are equal.