13-Mar-2020, 00:34
@David A - the reason I asked particularly about the jitter-related sidebands is that UpTone's white paper specifically said that they are an expected result of clock phase noise which the ER is meant to eliminate. Ground plane noise is the mechanism by which the clock phase noise causes the jitter sidebands, according to the white paper (not the end result). The ground plane is also said to carry noise caused by leakage currents, which would also be apparent at the DAC output.
So, these two causes (clock phase noise and leakage current), which happen to be carried into or through the DAC via ground plane noise, either cause significant perturbations in the output of the DAC or they don't. UpTone's white paper specifically says that "ordinary" switches will cause jitter-related sidebands in the output of the DAC, which is one of the things ASR's test was sensitive to, as well as other forms of noise and distortion. In other words, I understand that ASR were measuring exactly what UpTone say should be measured -- that is, what the white paper says the ER will change.
In short, if the perturbations described in the white paper are significant without ER, it lseems to me that ASR's test was properly designed and had enough resolution to measure them. That is what I was asking Alex to comment upon.
(Yes, there is a discussion to be had about what magnitude of effect is audible, but the measurements seem to show no differences with or without ER down to better than about -140 dB which I think we can probably agree is good enough.)
By the way, I did also say that I wanted to limit the scope of my question to the measurements themselves excluding the subjective comments or what followed; I agree with you that the latter parts had little value.
So, these two causes (clock phase noise and leakage current), which happen to be carried into or through the DAC via ground plane noise, either cause significant perturbations in the output of the DAC or they don't. UpTone's white paper specifically says that "ordinary" switches will cause jitter-related sidebands in the output of the DAC, which is one of the things ASR's test was sensitive to, as well as other forms of noise and distortion. In other words, I understand that ASR were measuring exactly what UpTone say should be measured -- that is, what the white paper says the ER will change.
In short, if the perturbations described in the white paper are significant without ER, it lseems to me that ASR's test was properly designed and had enough resolution to measure them. That is what I was asking Alex to comment upon.
(Yes, there is a discussion to be had about what magnitude of effect is audible, but the measurements seem to show no differences with or without ER down to better than about -140 dB which I think we can probably agree is good enough.)
By the way, I did also say that I wanted to limit the scope of my question to the measurements themselves excluding the subjective comments or what followed; I agree with you that the latter parts had little value.
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