iFi DC BlockerThe amplifier is the heart of your system. If you have a mechanical hum, deploy the DC Blocker. Got big amplifier. Bye bye mechanical hum. Many large amplifiers have a really annoying mechanical hum (emitted from the toroidal transformer itself). You can hear it when you place your ear close or next to the chassis. This is caused by a small amount of DC voltage in the mains which makes its way through to the mains transformer, it will become saturated