Mac engineers back in the 70s came up with a phono preamp EQ stage based on the new Signetics designed opamp that outperformed the much more common multiple transistor stages that they and others had been using.
Over the last 40+ years they have been refining and improving upon it.
There have been any number of phono amp stages over the years promising exceptional performance when a phono stage really just has to undo the analog degenerative EQ applied prior to the master being cut.
That EQ process was designed to use capacitance and resistors to lower the level of the bass and midrange in a predictable fashion using non active components in the 60s. That work was done by RCA who then formulated a active tube based correction circuit to recreate the original signal after the cartridge played the signal.
The RIAA EQ standard has held sway ever since.
Over the last 40+ years they have been refining and improving upon it.
There have been any number of phono amp stages over the years promising exceptional performance when a phono stage really just has to undo the analog degenerative EQ applied prior to the master being cut.
That EQ process was designed to use capacitance and resistors to lower the level of the bass and midrange in a predictable fashion using non active components in the 60s. That work was done by RCA who then formulated a active tube based correction circuit to recreate the original signal after the cartridge played the signal.
The RIAA EQ standard has held sway ever since.
