I understand it is good practice to twist pairs of wires together to help cancel out the negative effects of EMI. This is simple enough when dealing with a live/neutral or positive/negative pair but I've got myself into a bit of a muddle when trying to figure out which wires to twist together when transformers have dual secondaries. Here are two examples: My phone stage PSU calls for inputs of 22v-gnd-22v and the transformer has dual secondaries as follows: First secondary: Red - Black Second secondary: Orange - Yellow I have the Yellow and Red connected together to give me a centre tap so I now have: Orange - AC1 Yellow/Red - 0v centre tap Black - AC2 So which pairs of wires should I twist together? At the moment I have orange/black twisted together and yellow/red twisted together but is that correct? Example 2: I have a small 5v regulated PSU in my CDP. The PSU needs two AC inputs. The transformer has two secondary outputs labelled as follows: First secondary: Red 9v Blk 0v 2nd Secondary: Yel 9v Blk 0v I have red/yellow connected to input AC1 and orange/Black connected to input AC2. Again which wires should I twist together as a pair? I did warn you that it was a stupid question.