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RE: Fremer's ZENITH ANGLE CORRECTION or have we all gone crazy.

Posted by flood2 (A) on February 18, 2021 at 00:37:58

In Reply to: RE: Fremer's ZENITH ANGLE CORRECTION or have we all gone crazy. posted by John Elison on February 16, 2021 at 08:58:40:

I thought my reply to your question was very clear, but I will repeat the key sentence but this time with capitalised words of importance in case you missed them the first time around...

"In the case of the Ortofon test disc, the test signal IS PRE-EMPHASISED FOR RIAA therefore the output of a phono stage would be a flat signal within the tolerancing of the phono stage EQ."

Secondly, as I pointed out, the test discs in question assume that a conventional phono stage is being used, therefore pre-emphasis is typically applied to the signal whilst proper test discs made to the DIN standard are linear cuts without pre-emphasis at a reference amplitude of 11.25um for 0dB.
Pink noise is typically used for testing loudspeaker sensitivity and subjective response balance because the 1/f spectral noise power is closer to that found in natural systems to which the human auditory system is attuned to. Hence, sound engineers use pink noise to evaluate room response.
White noise is an equal amplitude signal and is therefore ideal for analytical measurements not involving the subjectivity of the auditory nerve centre. Pink noise is derived by filtering white noise with a 10dB/decade attenuation characteristic.

Your statement that a pink noise test tone will give a flat response with a magnetic phono cartridge is incorrect for the commonly available consumer test discs such as the HFNRR and AP Ultimate Analogue Test LP which assume that the user will play back through a standard phono stage.
Using the pink test signal from the AP Ultimate Analogue Test LP, the spectrum on the left is with flat gain and the spectrum on the right is the RIAA equalised signal with the frequency range zoomed into just below 1kHz to just above 10kHz. You will note that with flat gain the response is up ~4dB at 10kHz with respect to 1kHz. When RIAA EQ is applied, the response drops by the expected 10dB/decade and the cartridge tested shows a fairly linear response of the Pink Noise test signal

The RIAA emphasised white noise test signal yields a flat response as expected from the "equal amplitude" characteristic of white noise.


Regards Anthony

"Beauty is Truth, Truth Beauty.." Keats

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