A single-ended triode (SET) vacuum tube electronic amplifier uses a single triode to produce an output, in contrast to a push-pull amplifier which uses a pair of devices with antiphase inputs to generate an output with the wanted signals added and the distortion components subtracted. Single-ended amplifiers normally operate in Class A; the cancellation of distortion allows push-pull amplifiers also to operate in Classes AB or B without excessive net distortion. See power amplifier classes for a detailed discussion.
The term single-ended triode amplifier is mainly used for output stages of audio power amplifiers. The phrase directly heated triode single-ended triode amplifier (abbreviated to DHT SET) is used when directly heated triodes are used.
There are also single-ended tetrode, beam tetrode/beam power tube/kinkless tetrode, and pentode amplifiers with the same functionality and similar circuitry; e.g. this Mullard design.
An older, but quite different, use of the term single-ended was to distinguish tubes in which all pins were connected via the base from those that had a top cap for high-voltage (plate) or interference-susceptible (control grid) electrodes.
Read more about Single-ended Triode: Audio Power Amplifiers, Speaker Matching, Audio Quality, Estimating Power Output For A Class A1 Amplifier From Valve Specifications, Class A2, See Also