What Is this circuit ???

[kagliostro]

I've find the attached schematic on the web

There were no explanation and I'not able to understand what exactly It Is

The upper section looks like a Preamp with lo impedance output

But about the lower section I'm not able to understand what It do, which Is the pourpose

Any explanation or idea about ?

Thanks

Franco

[SEL49]

Looks like a preamp for a phono magnetic cartridge (pickup). It has switch selectable equalization.

[HotBluePlates]

RIAA Equalization Curve

Notice when Recording that Bass is cut (to keep the needle from jumping out of the groove), and Treble is emphasized.

On Playback, Bass is boosted to restore "natural Lows" and Treble is cut (reduces Hiss while also restoring "natural Highs").

There were several different curves used by different record-manufacturers, or standards-setting groups.


A Phono ("PH") signal was also weaker than other sources, and needed extra amplification.  The output of the PH-channel's EQ section feeds the rest of the preamp when the Selector is in the "PH" position.

[kagliostro]

Many thanks Friends, now I understand

Thanks you very much

Franco