Addressing the Class D bias

The “D” in Class D does not stand for digital. It was simply the fourth type of amp recognized and classified by the IEEE. The first was Class A, the second Class B, the third Class C, etc.

Contrary to the bias that exists among high-end enthusiasts and across the industry in general, the Class D design is not inherently flawed. The truth is that no existing designs have been able to reach the Class D's inherent potential for performance. It is not the technology that yields fine audio performance but rather the implementation of the technology. At Anthem, we agree that most Class D amplifiers are poor performers. However the M1 uses Class D amplification of a different ilk (see later section on Class D for a full discussion).

The M1 is not a digital amp!

There are no A/D or D/A converters in the signal path. The amplifier’s control system continuously varies the width of the output pulse train in direct relation to the analog input signal. In essence, a side-to-side variation in width is analogous to a signal’s more familiar up-and-down amplitude variation, not at all the same as a digital string of 1s and 0s where all pulses have the same width.

Exceptional efficiency

Much has been written about Class D amps having twice the efficiency of conventional amplifiers at full output, but there's more to this. Under normal conditions an amplifier operates at only a fraction of its full output capability. At 1/8th of its maximum output (the typical working level of an amplifier), our M1 is six times more efficient than a conventional amplifier.

Why doesn’t the M1’s power cord have a third prong?

Although more difficult and expensive to implement, Anthem has always used 2-prong AC cords to make installation easier.

A 3-prong cord is prone to ground loops if the system includes other 3-prong equipment or cable/satellite TV. For example: If the preamplifier uses three prongs it is grounded not only through its power cord but also through any non-optical connections to other 3-prong components. This can result in humming or buzzing through the speakers as well as video noise problems. The more elaborate the system, the greater the chance of a ground loop. With 3-prong equipment, balanced XLR interconnection is needed throughout and that type of interconnection is not always possible.

With a 2-prong cord, safety is maintained through either double or reinforced insulation. The next time you see a corded power tool, look for the double-square symbol. It requires more expensive wires on the live side and greater distance between live circuits and isolated circuits and chassis. The distance requirement also applies to spacing inside transformers, making them larger and more expensive. A 2-prong cord also requires a larger line filter because according to safety standards the line-chassis leakage current limit is ten times lower compared to 3-prong. Ironically, a higher leakage current allowance aggravates hum problems in 3-prong systems.

To clear up any final misconceptions, the earth ground provided by the third prong is not meant as a shield, it is a safety measure meant to trip breakers should a chassis become live as a result of coming into contact with a live wire.