@erik_squires: I am not sure I understand your comment about "selling that"? Do you seriously want to define line harmonics as noise?
They are generated by loads, such as AC units and refrigerators. In the typical harmonic frequency range at less than 1KHz, the big problem is line voltage changes affecting unregulated power supplies in most power amps, not the harmonics that are readily rectified and stored as energy by the power supplies in our stereo equipment.
In other words, if one is concerned about that band, one should monitor the RMS voltage from 60 to 1KHz, which is far more of a problem than line noise in the same frequency band. However, most low level audio products, such as preamps, CD players, DAC's, etc. have regulated power supplies so line RMS voltage changes in that band become meaningless; especially since the regulation in that band of any decent regulator these days is especially good. Power amplifiers rarely have regulated power supplies in the high current stages and are more affected by voltage changes in the line.
Beyond that band, especially above 10 KHz, the PSRR of most regulators starts to fall off and noise passing through the power supply does have a detrimental effect on sound quality.
The best way to measure this stuff is not using a meter but using a spectrum analyzer with an upper bandwidth around 30 to 100 MHz. That will give you the frequency of the noise and also the magnitude of the noise. With that, one could correlate which frequency spectrum affects which component the most and how it affects the sound quality.
They are generated by loads, such as AC units and refrigerators. In the typical harmonic frequency range at less than 1KHz, the big problem is line voltage changes affecting unregulated power supplies in most power amps, not the harmonics that are readily rectified and stored as energy by the power supplies in our stereo equipment.
In other words, if one is concerned about that band, one should monitor the RMS voltage from 60 to 1KHz, which is far more of a problem than line noise in the same frequency band. However, most low level audio products, such as preamps, CD players, DAC's, etc. have regulated power supplies so line RMS voltage changes in that band become meaningless; especially since the regulation in that band of any decent regulator these days is especially good. Power amplifiers rarely have regulated power supplies in the high current stages and are more affected by voltage changes in the line.
Beyond that band, especially above 10 KHz, the PSRR of most regulators starts to fall off and noise passing through the power supply does have a detrimental effect on sound quality.
The best way to measure this stuff is not using a meter but using a spectrum analyzer with an upper bandwidth around 30 to 100 MHz. That will give you the frequency of the noise and also the magnitude of the noise. With that, one could correlate which frequency spectrum affects which component the most and how it affects the sound quality.