"Eeyore" wrote in message
...


'Bell Labs' etc working invariably involved matched 600 ohm etc circuits
together with all the limitations thereof.

One of those accidents of history. Since the earliest amplifiers used in
broadcasting and recording were adapted from telephone repeaters (which
naturally had 600ohm balanced inputs and outputs) that became the de-facto
standard in pro-audio for more or less the entire valve era. And until the
advent of negative feedback it was hard to make amplifiers with low output
impedance anyway.

Liberating audio from that horrible restriction was one of the best things
that
ever happened for high quality audio.

More a matter of convenience than "high quality". There's nothing wrong with
600 ohm terminated lines except that you can only connect one load to each
source.

David.