A good power supply is just as important as the equipment itself. The fact is that every piece of audio equipment requires power. However, the voltage and current requirements of each component are usually quite different. Therefore, every single component requires its own power supply. Many products on the market have a built-in power supply and connect to power by using a simple power cord. If the power cord is not bundled with the product, I suggest purchasing a high-quality cable. Always purchase a fairly thick gauge power cord because the thin cables can cause excessive losses. This is especially important for components which require large amounts of current such as audio power amplifiers.
Other types of audio gear require connecting of a DC power source. This means that instead of alternating current which is available in the power mains, you require a power supply which supplies this voltage. Again, if the manufacturer does not bundle a suitable power supply, you will have to pick an appropriate supply yourself. When purchasing a power supply, you can either a get a linear power supply audio switch mode power supply. The main difference between these two power supplies is the way the voltage is being transformed.
Linear power supplies are usually preferred for audio equipment because they have less noise. They transform the voltage by using a fairly large transformer inside the power supply. The reason this transformer has to be very large is because the frequency of the mains power line is either 50 or 60 Hz depending on whether you are located in Europe or the United States. Low frequencies don’t require bulky transformers. As an alternative, switch mode power supplies create their own alternating voltage. As a first step, the AC voltage is rectified into a DC voltage. This DC voltages is then chopped up inside the power supply. This occurs by using a MOSFET transistor. The switching frequency of this transistor is usually several tens of kilohertz. As a result, the required transformer can be much smaller.
The transformed voltage is then rectified. However, this switching stage inside the power supply causes a lot of noise. This noise is output on to the DC connector. Therefore, many power supply manufacturers will introduce filtering elements such as inductors and capacitors in an attempt to reduce that noise. So what type of power supply you select really depends on the type of audio equipment. Many power amplifiers by necessity require a switch mode power supply because a linear power supply would be too bulky. Many digital amplifiers are fairly immune to noise on the power supply line. However, many amplifiers usually are quite susceptible to noise on the power supply and thus don’t work very well with switch mode power supplies.