The foregoing techniques clean up AC to some extent depending on how many capacitors and types of filters are used, but do so basically after noise of various kinds has already been injected into the power lines by all the plug-in devices in the house. Virtually all household appliances, TVs, radios, computers, burglar alarm systems, lawn sprinkler control system, etc., etc., further pollute the already noisy AC power reaching the system.

Many of these devices have power supplies and digital processors running continuously and injecting noise into AC and neutral even with the units switched off. As many of these units as possible should be either switched off or preferably, unplugged for any listening session. Some may think this is ridiculous, but unplugging the TV, lawn sprinkler system and burglar alarm, for instance, makes a really big difference comparable to parallel capacitive AC filtering.

Doing this is well worth the inconvenience to an audiophile perfectionist. For more convenience, external power switches and mechanical timers can be added. Such external switches should interrupt both AC and neutral. Of course, this issue is greatly subject to the obvious constraints imposed by practicality and the power of your spouse to impose some degree of sanity.