I am talking of the power conditioner. A power conditioner will correct problems with power supply that introduce noise into your sound equipment. Wiring in a building might be bad, motors, compressors, thermostat switches, fluorescent lights, some incandescent lights, even the activities of the power company as they load balance the grid; all of these cause what we commonly refer to as dips, spikes, brownouts, surges that supply incorrect voltages and can disrupt the frequency, and phase, introducing harmonic interference into the power supply, which you will hear as undesirable pops, buzz, crackle or hum.

The function of power conditioners vary based on the manufacturer, but in general they should do the following:

• Correct undervoltage … commonly called dips or brownouts.
• Correct overvoltage … commonly called a spikes or surges.
• Correct harmonic and frequency variations … commonly called clean versus dirty power; power should follow a perfect sine wave pattern, but there are often problems with supply, or electromagnetic interference introduced into the building wiring that can change the frequency or phase of the wave form (harmonics).

By filtering and cleaning power that is supplied to your audio equipment, your audio will sound better, and you will extend the life of your gear by protecting the internal electronic components from added wear created by bad power.

Power conditioners are not surge-strips or multi-plugs. A surge protector usually only protects for overvoltages. A power conditioner performs the functions of a surge protector, while also filtering out dirt or harmonic contamination in the power supply. They come in rack mountable formats, but you can also find more affordable units that resemble a surge strip or a multi-plug. You may in fact want to consider this for your home theater setup also.