My original post was a happy one about enjoying the music on the HK 3490...You brought the confusion and wasted the popcorn.
When I accidentally tripped over this thread/topic again, I thought I should try one more time even though I said I would move on before. This is to help avoid others getting mislead by your claim that Gene actually measured SINAD, when afaic he in fact measured SNR. Again, the two are not same, though related to certain extent. SINAD is the inverse of THD+N, that clearly is not the same as SNR.
You first claimed the following in your "original post":
"Yes. I assumed the measurement I quoted actually refers to SINAD, that is to the ratio (signal)/(noise +THD). This is consistent with the AES17 standard that was quoted for this "SNR" measurement, although the standard actually includes ALL distortion, not just harmonic distortion."
(2) harman/kardon HK 3490 Stereo Receiver Review | Page 7 | Audioholics Home Theater Forums
and repeated in other posts as well such as post#129,131,133 and then 137 posting part of the AES17 standard.
You pasted a small part of the standard but not enough to show the difference between the two so I am pasting more below for those interested to see the difference.
Here's the link you provided:
STANDARDS AND (tu-berlin.de)
8.5 Total harmonic distortion and noise (THD + N)
NOTE The characteristic to be specified is the transfer characteristic and dynamic non-linearities in
the EUT. The results are indicative of anomalies in device behavior but may not be indicative of
audible performance.
Harmonic distortion and noise is the ratio of the output noise and distortion level to the output signal level.
Both levels shall include all harmonic, inharmonic and noise components. All components shall be included
because harmonics often alias above the folding frequency and often appear anywhere in the audio band.
8.5.1 Total harmonic distortion and noise versus frequency
The measurement should be conducted with a sine wave at
– 1,0 dB FS and repeated with a sine wave at
– 20
dB FS. The test signal present in the output should be removed by means of a standard notch filter and the
remaining signal bandwidth limited to the upper band-edge frequency or 20 kHz, whichever is lower. The
level of the filtered signal should be measured and reported as a ratio to the unfiltered signal level. The
measurement should be repeated at each octave frequency from 20 Hz to one-half the upper band-edge
frequency. Since you mentioned "..in the presence of signal...", I included the sections that I believe are relevant to the discussion.
9 Signal-to-noise measurement
9.3 Signal-to-noise ratio or noise in the presence of signal
NOTE The characteristic to be specified is the ratio of the full-scale amplitude to the weighted r.m.s.
noise and distortion, expressed in decibels, in the presence of signal. It includes all harmonic,
inharmonic, and noise components. It is identical to a measurement of noise in the presence of signal.
The test signal for the measurement shall be a 997-Hz sine wave producing
– 60 dB FS at the output of the
EUT. Any 997-Hz test signal present in the output shall be removed by means of a standard notch filter. The
remaining noise shall be filtered with the standard weighting filter. The measurement shall be limited in
bandwidth to the upper band-edge frequency or 20 kHz, whichever is lower. The resulting measurement shall
be read as dB FS and reported as dB FS CCIR-R.M.S.
Anyone who spent time to read carefully would know THD+N and SNR are defined differently. It seems that you are fixated on the words in Section 9.3 where it says "It includes all harmonic, inharmonic, and noise components...." and ignore or neglected the part "It is identical to a measurement of noise in the presence of signal."
The fact is, when you measure the noise, any harmonics included (from distortions) would be very low (I think you mentioned that too) because there is either no signal being applied, or as per the AES17 standard, at -60 dBFS level, so the amp isn't amplifying anything or just a small signal, and then when you applied the "full-scale amplitude" signal, the contribution of the distortions to the max voltage would be naturally low. With SINAD (reciprocal of THD+N), the test signal in the output is removed, so the measured distortions would matter a lot obviously.
Aside from the above, I would like to clarify my point that Gene's graph made reference to AES17, but I believe that merely reference the weighting or bandpass limit filters (if used) for the measurements would be in accordance with that standard, and it does not necessarily mean he following the Section 9 of the standard. My educated guess is that he likely follow the AP procedure as that's the instrument he used and trained on. And in this case he did mention, "no weighting".
Below is from the AP website:
Signal-to-noise Ratio (SNR), Dynamic Range, and Noise - Audio Precision (ap.com)
"In a conventional SNR measurement a device is first stimulated with a signal at full scale with its volume control set to maximum, if present. A level measurement is made to establish the maximum output reference. The stimulus tone is then removed and the inputs of the device are either terminated or shorted. The residual noise is then measured. The SNR value is then the ratio of the full scale output level of the device to the residual noise level of a device."
More about THD+N and THD - Audio Precision (ap.com)
"For THD+N Ratio, the rms level of the measured distortion plus noise (the signal with the stimulus tone removed) is divided by the rms level of the total signal. The result displayed on a bar meter or as a point on an XY sweep graph. THD+N ratio is most often stated in as a percentage or as a decibel value, where 0 dB represents the total signal. "
AP also made the point I am making here on the distortions part:
More about Signal-to-Noise Ratio and Dynamic Range - Audio Precision (ap.com)
"FOR DIGITAL CONVERTER MEASUREMENTS…
We recommend using this AES17 dynamic range measurement. It is intended specifically for ADC (analog-to-digital converter) and DAC (digital-to-analog converter) dynamic range and “noise in the presence of signal” measurements, as described in Section 9.3 of AES17. A similar method is defined in IEC61606.
This method differs from standard signal-to-noise and dynamic range measurements in that it uses a –60 dBFS stimulus during the noise measurement. This method is used for two reasons:
· In both ADCs and DACs, “idle tones” can be produced within the converter in the absence of applied signal. In the method here, a low-level tone is applied to the converter to avoid production of idle channel noise. The low-level tone is removed by a notch filter before measurement.
· In some DACs, the output of the device is switched off when there is no signal, providing an unrealistically quiet measurement. The low-level tone (again, notched out before measurement) defeats this muting mechanism.
"At –60 dBFS, the tone is so low that any distortion products created are below the noise floor."
And of course, THD+N is the reciprocal of SINAD.
It is amazing so much has to be said, when it should have been clear to anyone that THD+N (or SINAD) is not the same as SNR, if they were, people wouldn't be doing both measurements and manufacturers specs would not have included both in any case.
