Sometimes it&#x27;s all about tradeoffs. For example, a split bobbin is actually undesirable in most transformers because it reduces coupling between the windings, reducing the efficiency of the power supply. That&#x27;s why if you look inside a better-quality power supply you&#x27;ll often find that they have a split bobbin for the input common-mode choke and then a single bobbin with layered windings for the main transformer.