Guidelines
Classes:
The classes in which are working output elements of the amplifier:
- class A (used since 1917) and its modifications
- class B and class A-B(1945) and its modifications
- class C is not for audio, it is for RF
- class D (used since 1963 ) so called “digital” or “PMW”
- class E is not for audio
- class G (used since 1977) uses two different voltages for the output elements - either it is working in low power or in maximum power regime.
- class H (used since 1983 ) includes A and B classes, and its modifications
- class S which is used for evaluations of connections of the lamps and semiconductors, without lamps to be connected to them
Features:
Class A:
- Pros: Ease of low distortion, both static and dynamic Cons: High hardware cost, high weight, high electricity cost, high heat output, power capability practically limited to about 100 watts.
Class B, A-B, A-B1, A-B2:
- Pros: Simple circuitry, low hardware cost, medium electricity cost. With good design and application to ameliorative tools, almost as low a distortion as class A is possible. Cons: The reference condition.
Class Super A, π-mode, Dynamic and Plateau biased-A.
- Pros: Potentially lowered dynamic distortion over ordinary B and A-B types. Much of the class A advantages at some fraction of the cost. Cons: Slightly more complex circuitry than A-B. Topologically more limited. Higher electricity cost and heat output if quiescent periods dominate, but still much lower than class A types.
Class C:
- Radio Frequency amplifiers only, not for audio.
Class D:
- Pros: High efficiency, lightweight, potentially low hardware cost, Cons: Complex circuitry, sonic performance may be poor, particularly above 5 kHz, EMI emission likely.
Class E, F:
- Not for audio.
Class G, H:
- Pros: Both permit high transient power capability. Usefully higher efficiency than class A-B under medium to hard-drive conditions. Cons: Slightly more complex circuitry than A-B. More PSU parts and hardware and higher build cost. Added dynamic distortions possible (but well containable in practice) due to multiple-supply switching and finite part matching. In inexpert designs, multiple power supplies might be improperly apportioned, leading to wasted hardware and unsuitability with some programs.