How can I (conveniently!) verify the signal-to-noise ratio (relative to 1.0Vrms) specified for a power amplifier when the maker states that the measurement is "A-weighted"?
Yes, I do know what A-weighting implies (see fig. 2.5 of "The Audio Expert"), and I'm aware that I could construct an A-weighting filter (see Elliott Sound Products, sound-au.com/project17.htm) for use with my Fluke 87v AC voltmeter, but I find it hard to believe that everybody does this when they simply want to check the signal-to-noise (re. 1.0Vrms) reading.
What's the general ongoing practice? Do techs generally just resort to the use of the built-in low frequency filter input on their Fluke AC voltmeter? Is there some commercially available accessory probe for voltmeters that approximates A-weighted response? (I can't find any such device.) Is there some reasonably priced (i.e., not Audio Precision) low end means of reading the requisite value (10 µVrms for a s/n ratio = -100 dB)? How does the trade handle this noise measurement when "A-weighted" is referenced?
It was my expectation that Ethan Winer would respond, as he notes (elsewhere) that this is the place to post such inquiries.
Others might be interested in this…
Signal-to-Noise Ratio in dBV (Measured noise referred to 1.0 Vrms.)
…noise = 100 µVrms, s/n ratio* = -80 dB (x10,000)
…noise ≈ 31.6 µVrms, s/n ratio* ≈ -90 dB (x31,625)
…noise = 20 µVrms, s/n ratio* = -94 dB (x50,000)
…noise = 10 µVrms, s/n ratio* = -100 dB (x100,000)
…noise = 3.16 µVrms, s/n ratio* = -110 dB (x316,455)
*Often stated as “A-weighted”, with input shorted.
Note that Parasound’s A23+ power amplifier (circa 2018) specifies s/n ratio as… …s/n ratio > 112 dB, input shorted, IHF A-weighted. —and— …s/n ratio > 107 dB, input shorted, unweighted. So there appears to be ~ 5dB advantage when the s/n is measured “A-weighted”.