HiFi source components are very sensitive to electrical pollution and mains voltage fluctuation because the audio signal they produce is at a very low voltage, and this signal must be amplified in order to drive the speakers. Amplification is achieved by using the incoming mains supply to electronically boost the signal, and a polluted mains supply will prevent the electronics from your HiFi equipment from operating as intended. This causes a cascade effect within the electronic circuitry, resulting in a polluted amplified signal.
To get the best from your system, you must provide each front-end component such your amplifier and sources such as CD players and turntables with a conditioned, isolated, pollution free and a pure sinewave electrical supply. This can be achieved with a separate power supply. The basis of incorporating these extra modules within your system is to reduce distortions in the sinewave contained with the AC supply to the home, as well as reducing the unwanted radio signals (RFI) which are superimposed on the average electrical supply. One extremely important aspect of secondary power supplies is the ability to produce on demand a clean and extra boost of available power when an amplifier is at its limits particularly when reproducing lower frequencies which need extra power to control the base line, extra benefits include having an ample reserve for the most demanding music.
Electricity demand is subject to fluctuations on a seasonal basis, across the week, and during the day. Demand can also be influenced by irregular events, such as particularly extreme weather conditions. So for example during cold weather and during peak demand times, your mains supply will vary considerably. Voltage variation in the UK is ridiculously high and very common and unfortunately, it’s also getting worse. Government regulations force the electricity generation board to maintain a 240 volt 50 c/s plus or minus 10% so a peak maximum of 264 volts and a minimum of 226 volts are allowed so appreciate how your sensitive Hi-Fi products are going to behave with this variation, and this variation will only get worse as the supplies get more eroded.