Quote Originally Posted by Mr Peabody
Class D uses a digital switching power supply, so they do not have the heat or weight of a class A/B. ...
Some Class D or "digital" amps don't have switching power supplies and some Class A/B amps do, the latter are sometimes referred to as Class H (I think: ?? ).

My former Bel Canto eVo amp was Class "T" for Tripath, a proprietary variation of Class D; it had a standard "linear" power supply, not a switching supply.