Single ended amplifier: In the single-ended design, the complete music signal (i.e. the entire wave) described by AC voltage is amplified by one and the same active component. This does not necessarily mean that only a single active component is actually working on the output side - even if this is often described as such.
Rather, it is decisive that the music signal is not split into its two half-waves, as is the case with push-pull amplifiers (also push-pullamplifier called) is the case. In the case of the latter, the negative and positive half-waves are amplified by other active components, and this is the crucial difference to the single-ended.
The prerequisite for a single-ended design is therefore the shifting of the operating point to the middle of the characteristic curve of the active component - hence Class A operation (the reverse is not necessarily true).