A phono preamp with equalization selector

Here is the HK Festival monaural tube tuner from early 1950s.  My memory of its built in equalization curves was faulty; the photos show "Eur", "RIAA", and "LP", not Columbia or Decca.  I wonder what were the differences between Eur or LP vs RIAA.

Look up the Harmon Kardon Festival monaural receiver. That’s what my parents had as of the early 50s, even predates the unit shown above. As I mentioned, it provided a choice of EQ curves including RIAA, Columbia, Decca, and maybe one other. I’m guessing that this is because the industry was just settling on RIAA during the period 1948-55(?). I do recall fiddling with the EQ in order to hear the differences. So maybe if you own very early production mono LPs, there might be a marginal benefit; the different EQs did not seem to make much difference to tonal balance, to my pre-teen ears.

GHD, You say "used in the 40s and 50s".  For most of the 1940s, the 33 rpm LP as we know it today did not yet exist.  I think the very first such records were produced in 1948-49.  It was the introduction of this then new technology that necessitated the new equalization curves. 78s and whatever else was in common use through most of the 1940s were certainly not equalized according to any of these algorithms.  From there, I refer you to the article by MF that I referenced above. Whatever one might think of MF in terms of his opinions as an equipment reviewer, I do trust him to do a thorough job of research when he addresses these general subjects that apply to the hobby.  I take Ralph Karsten's (Atmasphere) word as well, that the companies that made the equipment upon which LPs were cut (Westrex, etc) who determined what equalization curve to use, and that all of these companies had adopted RIAA by the mid-50s. (Yes, I suppose there are rare exceptions, but I don't know of any, and maybe they did it differently at first, in the UK.)

Of course that is possible, but do you think it really has to do with the "1980s"?  More likely that a single particular recording regardless of the time line, might by chance sound "better" using an equalization curve other than RIAA. (And Columbia is not far from RIAA, anyway.)  And besides, what does "better" mean? (It's a subjective judgement.) The point is that nearly all companies (I say "nearly all", because I don't doubt that someone can find an exception or two) used RIAA certainly by late 50s/early 60s.  I think Fremer is claiming RIAA took over even earlier in the history of the LP. In the early or mid-50s, my parents had a Harmon Kardon mono, tube receiver that offered RIAA, Columbia, and one or two other choices for equalization, but note the date.

You peaked my curiosity as to whether there is some new information pertaining to equalization curves used in the earliest decade or so of 33 rpm vinyl LPs.  (So this has nothing whatever to do with any record that is not in that category.)  You might be interested to read what Michael Fremer had to say on this subject, with documentation of his position:

Note he specifically mentions Deutsche Gramaphone LPs.

You must be a youngster. 60s and 70s were the haydays of vinyl and by then all companies pretty much had settled on RIAA equalization. You have to go back to the 50s and late 40s (the advent of the 33rpm LP) for divergence in equalization. I always played DG LPs with RIAA. Never heard of Teldec equalization. Maybe someone else can help.