What HiFi amplifier? What type to choose?

Ever wondered what the difference is between Class 'A', Class 'AB' and Class 'D' HiFi amplifiers? What's the difference in their sound and what should you look for when choosing an amplifier for your system? Also (from 38:17) Harley Lovegrove, the technical director of the loudspeaker company 'Pearl acoustics Ltd.' talks about how sound is converted into electricity and how that is amplified so that the loudspeaker's drive cone can convert the electricity back into sound. The video is interspersed with clips from the charity work for young classical musicians that Pearl Acoustics invests a sizeable proportion of its profits in.

(The intro. and outro music is 'Philia' written and performed by Stefan Meylaers, and taken from his piano suite 'The Four Loves').

Editorial 'errata' note: During this video I refer to 'Push-Pull amplifiers and attribute them to Class A-B amplifiers. This is not always true, and in fact I failed to mention that 'Push-Pull designs can be used in Class 'A', 'AB' or 'B' design. For example; in some Class 'A' amplifier designs, pairs or multiples of transistors (or Tubes) are configured in such a way that they start off in Pure Class A but switch to supplying their current in both directions (push-pull), once a certain output current is used. Sorry if any confusion was created. Thanks to those who took the time to comment on this topic.
Here is a link to a Nelson Pass article on this topic: https://www.firstwatt.com/pdf/art_lea...

More about Pearl Acoustics:
Discover more about Pearl Acoustics, who we are, what we do and what we believe in:
Pearl Acoustics website: https://pearlacoustics.com/
Our loudspeakers: https://pearlacoustics.com/loudspeakers/
Our 7040 amplifier: https://pearlacoustics.com/products__...
Our 170 amplifier: https://pearlacoustics.com/products__...
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Disclosure: All comments and claims in this video are the opinion of the presenter and are given independently of any external company or organisation. Unless otherwise explicitly stated, the presenter does not receive any payment, gifts or other incentives from any of the companies featured in this video. All equipment in this video has either been purchased by the presenter or is on loan to him expressly for the making of this video.
All facts, figures, prices and technical specifications are quoted on a best-efforts basis for accuracy, no liability can be accepted for any errors therein.