The single-ended triode (SET) uses a single triode to make an output, not like the push-pull amplifier with a pair of their antiphase input device with the distortion components subtracted and the wanted signals added. SET amps usually works in class A amps, the distortion cancellation approve push-pull amps also to work in class AB or B without too much excessive net distortion.
Many small-signal audio and radio frequency tube and hidden transistor amps are single-ended, different from balanced class A.
The term single-ended triode amp is commonly used for output phases of audio power amplifiers. The term directly heated triode single-ended triode amp (DHT SET) is used referring to directly heated triodes are used.
There are also amps with same functionality and similar circuitry like the single-ended tetrode, beam tetrode/beam power tube/kinkless tetrode amps.
A much older but doesn’t quite the same use of the term single-ended was to explain tubes in which all pins were connected through the base from those that own a top cap for high-voltage (plate) or interference-susceptible (control grid) electrodes.
Now lets talk about the audio quality, the SET amps are categorized as a classic design in few audiophile and have their own place because of the excellent mid-bass performance, musicality, and directness. The simplicity and minimalistic approach of the circuits involved and the triode amplifying tubes that are typically used attributed a high sonic quality.
Compared to high feedback amps, the configuration will generally provide higher measured distortion performance. The distortion is predominantly second harmonic which is pleasant to the ears. This second harmonic distortion is canceled in the output transformer in a push pull amps. Few percent THD is usual at full power output, but at normal music level it will be lower. Audiophile agree that when global feedback reduces distortion across the harmonic range, it also reducing dramatic dynamics connected with a SET amp and the the highly efficient speaker needed so that we can enjoy a low power amp.
