The concept references the album's use of older, but not obsolete, and (arguably) superior recording technologies: tube amplifiers, and the direct to disc recording process.
the Ultra-Linear output stage (a tapped push-pull output transformer providing power intermediate between triodes and pentodes, at lower distortion than either) was originated by Alan Blumlein in 1937 in the UK, but popularised following publication of a paper by David Hafler and Keroes in the USA in 1951, and became the dominant topology during the post war recovery of consumer products
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