As an industry lifer since 1973 with more experience in "mid-fi" than I care to admit, I define the term by recognizing the following: Mid-Fi is not made by a brilliant but misunderstood savant designer...it's made by an industrial manufacturer with economies of scale helping to keep cost per unit down. It eschews "boutique" parts like designer capacitors, silver plated wire and Teflon insulation. It performs well enough to comfortably pass conventional performance measurements. It is well designed enough and well finished enough to give the appearance of high quality, at least on the surface. It has an assortment of inputs and outputs to satisfy the needs of a diverse audience that includes most people.
These attributes could have been equally met by a Marantz 7/8 or McIntosh C22/MC275 as by a Pioneer or Sansui receiver. If the former were High End, they still met all the mid-fi criteria, just with better sound quality.
The modern concept of High End, with its snob appeal, exploded in the mid-70s with the arrival of Mark Levinson's 25W mono-blocks, 4-chassis linestages (2 separate VCs!) Wima caps, LEMO connectors, etc. Gone wer convenience and practicality, affordability was not a concern, and personality cult status for the designer fueled the myth.
As Asian made mid-fi brands got more comoditized and glitzy, entry-level high quality audio slipped in to restore original mid-fi values...NAD, Hafler (both Dynaco and his own name-brand), Adcom, Rotel all had their runs.
On the other end you had B&O where looks were everything, and Bose where specs were nothing.
I could go on...
