IN digital tuner TO analog tube pre-amp TO b&o penta speakers OUT
Penta boxes, tube tuner (2x mono), and digital tuner (android phone) work fine separately. When joined, they produce a nasty 50 Hertz noise in the background. The boxes are in the space - I will bring in the other parts for a test set-up. In the end I want to use it as sound system in my apartment (again).
That is almost certainly an earth-loop (aardlus). Read up on it. You can combat these in two ways; one is cutting any double earth paths, but you MUST keep safety in mind, so never severe the earth/ground wire of mains equipment! The other way is deploying a (de)coupling transformer in the signal path, those can be had from an electronics shop. Ultratux 00:35, 19 August 2013 (CEST)