|The following is an excellent description of the RIAA Record Playback equalization curve, which you correctly covered.|
However I agree with the Author of the next article, although he seems to get somewhat over excited about non RIAA equalization curves, supposedly used in the early 1950's .
While serving in Northern Japan in the mid 50's I was able to locate components, and documents for high quality Mono High Fidelity amplifiers made by a company known as Sansui ....
such activities kept me off the muddy back streets and out of certain "establishments" in that GI town.
and gave me a somewhat basic knowledge of this stuff.......
Those early vacuum tube components used simple RC Circuits (ie Resistor & Capacitor combinations to Boost the low (bass end) which had been severely attenuated to avoid the problems which you and the author of the first article describes.
He also noted that the high end (treble) frequency end was boosted prior to cutting of the original recording to overcome surface noise introduced by the recording material.
I would not describe this procedure as introducing any kind of "loss" .
Rather , it is simply applying specific degrees of boost and attenuation in decibels.... during the recording and playback processes.
Simple bass and treble controls in these devices were also resistor/capacitor RC circuits, utilizing audio taper audio taper (logarithmic ) potentiometers (resistors with knobs) ,
which also served primarily to to "boost" both ends of the audio spectrum (about 30 to 20,000 CPS / cycles per second /Hertz , to compensate for losses in our moving paper cone speaker systems.