Here is a quote from tle Lenard Audio website
Myths and facts. To appreciate valve technology we must first be-bunk audiophile myths that in-correctly describe them. Many Audiophiles believe in alchemy and behave similar to religious cults. Cult driven audiophiles are easily identified by their repetitious chanting of brand names, model numbers and meaningless superlatives concocted by high priest reviewers and marketing departments. The highest Deity worshiped by the occult audiophile is the Single ended Class A valve amplifier. These amplifiers have one 1930s style large triode per channel. They are extremely in-efficient, average 3 to 20 Watts and often generate excessive 2nd harmonic distortion. The reason for worshiping one output valve, is same reason the religions of Abraham worship one God. These single ended amplifiers can be decorated with gold, and interconnected with oxygen free cable which channels Orgone energy (un-used sexual energy) from the lost city of Atlantis, enabling anything connected to the cable to transcend the laws of physics. Many of these cult objects are faddish nonsense and a few are beautiful works of art. The right pic is the KronzillaSX amplifier by KRaudio.
Audionote has a range of single ended amplifier DIY kits showing their internal construction.
Some single ended valve amplifiers today, including replications of early triode valves are made by enthusiasts demonstrating the craft and skills similar to enthusiasts who replicate old grandfather clocks and steam engines. Some of these hand crafted single ended amplifiers are highly valued by collectors and as stated earlier can be beautiful works of art. This craft of demonstrating the skills to create technology of the past must not be confused with modern technology and science.