On May 14, 10:21 am, John Byrns wrote:

No, you have that exactly backwards, the RIAA recording curve reduces
the groove amplitude at high frequencies, requiring a complimentary high
frequency boost in playback, which increases the effects of surface
noise.

From: RIAA Equalization Curve for Phonograph Records
By: Don Hoglund

http://www.graniteaudio.com/page5.html

However, because the cutter head's movements translate the amplitude
swings of the original signal into velocity - the rate at which the
stylus moves during its swings - low-frequency signals would be
recorded with a much larger swing than high-frequency signals of the
same original amplitude. So, the low frequency grooves would be much
wider than the grooves on an equalized disk. Wider grooves take up
more room which reduces the available recording time. They are also
much harder for the cartridge to track which increases distortion.
***The solution is to reduce the amplitude of low frequencies during
disk cutting and then boost them with a reverse curve during playback.
***

Another problem is distortion and signal-to-noise ratios in the high
frequencies. Early disc recording equipment did not have the extended
high frequency capabilities of today's modern equipment. However, as
disk cutters improved during the 1940's through the 1960's the need to
address the high frequencies increased.*** The solution was to boost
the high frequencies during cutting and then reduce them during
playback.*** Now there was a high and low curve with a "knee"
frequency.

Asterisks are mine.

The two curves superimposed at the end of the article are interesting.
*Boosted* on recording. *Reduced* on playback.

Peter Wieck
Wyncote, PA