It's common for most amplifiers to have a disturbing mechanical transformer hum. Caused by a small amount of DC voltage reaching into the audio mains, this hum hinders your music listening experience and that's where the iFi Audio DC Blocker comes into the picture. When you place the DC Blocker at the IEC (at the rear power inlet), the DC blocker does as its name implies, it blocks DC from entering into the audio mains. It is designed to discard transformer hum from all sorts of amplifiers. To get the best result it is ideal to use the DC Blocker with one direct power cable connection. Kindly note that the DC Blocker does not affect the EMI shielding or the safety of any equipment you are using it with.