We're normally calling a mains transformer a "Transformator" here, while an audio transformer is a "Uebertrager".
Nevertheless, the short form for the mains transformer is "Netztrafo", while "Eingangstrafo" and "Ausgangstrafo" are also common for (audio) input and output transformers.
But then again, we're also calling electrolytic capacitors "Elkos". (;->)
[quote author="jhaible"]But then again, we're also calling electrolytic capacitors "Elkos". (;->)[/quote]
They are called "lyt" (or "lytter" is there's more than one) in Denmark...