An alternative to the full DIY mains filter build in the previous article is to use a standard chassis filter make by either Roxberg or Schaffner. These are off the shelf parts that come assembled in a metal box with input and output tags for L, N,E. They can be selected based on the current rating you require and have various choke sizes.
Choose a filter with a large inductance choke (10mH) for a source component filter like CD players, DAC, pre-amp or small integrated amplifiers for example. Use a smaller inductance (higher current rating such as 10A) for large dedicated power amp filtering. A mid range inductance (5mH) is fine for a computer based filter or more general audio use. The chassis filters can be bought from RS components, CPC and even on ebay occasionally.