Усилители из Европы конца 60 начало 70.

The RIAA equalization curve was intended to operate as a de facto global industry standard for records since 1954. However, it is almost impossible to say when the change actually took place
http://en.wikipedia.org/wiki/RIAA_equalization

THE BIRTH OF THE LP - 1947-1958: With the new slower rotation speed and a new material (vinyl) to make records out of, a new set of recording curves emerged. The first two, LP and NAB, were derived from the National Association of (Radio and Television) Broadcasters (NAB, or NARTB) curve, which was used to make acetate radio program transcriptions.

The Columbia LP curve adds the rumble shelf, to reduce the effect of turntable rumble. Turntable rumble increased with slow rotation speeds and smaller grooves. But the treble boost from these curves was so much that it caused mistracking in cheaper cartridges. This caused some record companies to adopt more gentle recording curves.

One was designed by the Audio Engineering Society (AES), but the surface noise on records cut with that curve was excessive. Then RCA stuck its nose into the mix with the 45 RPM record, with an entirely new curve as well as a new speed and center hole size. As a result, several different curves were adopted by different record companies.

By this time, hi-fi enthusiasts clamored for the record companies to publish this information, so the user could adjust his set to handle each curve correctly. Most 33 RPM records made after 1951 have information on which curve to use printed on the label or the jacket, and most 45 and 78 RPM records didn't.

THE RIAA YEARS - 1952-present: Hi-fi enthusiasts called for a single curve that all records would be made in. In 1952, RCA developed the New Orthophonic curve with all of the solutions to problems listed above compounded into one set of record and reproduce curves. Within a year, the Recording Industry Association of America (RIAA) adopted this curve. By 1955, most American labels had adopted the RIAA standard.

The only changes to the curve were definitions adopted in 1974 to set the ultrasonic and infrasonic characteristics of records and playback pre-amps. This change was prompted by the introduction of the CD-4 quadraphonic disc system with its ultrasonic carrier. Note that some European companies did not make the change to RIAA until the 1960s, and some Russian and Asian companies didn't standardize until 1975.

Ну это стандарт 78 г. , действующий поныне . Там расширена полоса вч и введена коррекция ниже 20 Гц .

ссылочку можно ?