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His null control is rather... funny. I actually did a spice simulation on it (fig.3). It seems his null control can kill a 0.005V difference in the inputs, which is -43dBu before his 80dB gain. I didn't go higher because of time. That will be damn loud after 80dB gain!
In addition, I think there is an obvious problem in his practice. He used a source that only does ~65dB in SNR. Despite his equipment is 110dB in SNR, I don't think he could ever achieved a detection resolution higher than his source is ever capable of. However nobody ever questioned that.
In addition, I think there is an obvious problem in his practice. He used a source that only does ~65dB in SNR. Despite his equipment is 110dB in SNR, I don't think he could ever achieved a detection resolution higher than his source is ever capable of. However nobody ever questioned that.
Yes, you wrote that before, but I think you are mistaken. It does not matter what signal/noise that source has, since it gets split into equal parts for the two channels under test, and only the difference between those parts is what matters.
You could start with a white noise source, i.e. S/N ratio of zero, and the test would work nicely. If the two signal paths are identical, the two noise signals cancel out in the end, and you have demonstrated that the paths are identical (which is the point of this test).
Where you do need good quality components is in the parts of your test jig which are not identical between the two channels. A good differential amplifier, or inverter and adder, is important: You want to make sure that any measured differences between the two channels are indeed down to the transmission channels, and not due to your way of taking the difference. You can easily verify this by testing with two know-to-be-identical signal paths (e.g. two identical shielded cables).
I don't get it. Say if we put a terrible source that only output noise into the test jig. We will still get noisy out of the jig, even if we assume that cables make a difference. Does that make sense?
If it doesn't matter, it says that you are able to make a valid measurement of 0.0001V with a device that displays only 0.01V
I don't get it. Say if we put a terrible source that only output noise into the test jig. We will still get noisy out of the jig, even if we assume that cables make a difference. Does that make sense?
If it doesn't matter, it says that you are able to make a valid measurement of 0.0001V with a device that displays only 0.01V
You take a signal (any signal -- audio from your MP3 player, white noise, whatever) and split it into two equal parts. You send one part through cable A. You send the other part through cable B. At the outout ends af cables A and B, you let a differential amplifier take the difference between the two signals which have passed through A and B, respectively.
If the signal propagation through A and B is identical, that difference will be zero. That is true no matter what test signal you sent in.
Your difference amplifier (or output bridge) must be decent, and you must have a decent way of measuring low-level difference signals. But your signal source does not matter.
kris2014, either you are missing the point here, or maybe I am.
In my understanding, the whole approach here is a differential measurement, i.e. you compare one cable with another one and look at the difference of the signal only. If there is no difference when comparing some stupid "high end" cable with a standard one, you have proven that the "high end" claim is bollocks.
As I have tried twice to explain in the above posts, you can run this comparison with any old signal, and hence any old signal source. If there is noise in the signal, the two signal paths will both faithfully transmit the same noise, and it will cancel out at the output (with high precision).
Anway, I have tried to expain this threee times now. If this still makes no sense, I better let someone else have a try.
In your video, after nulling you still have a strong signal in terms of amplitude versus your background. That said, you have not null out the difference after all. If they cancelled perfectly, why would your output signal several times stronger than your background?
2 observations:
- around 18min. of the video he highlights the quality and the importance of the quality of the cables he built, to intend to demonstrate in the end that cable differences are placebo. I'm I getting this right?
- "puff"? Never heard that. Is that a short for "Hufflepuff"? To much Harry Potter I guess. Sorry.
Please read this IEEE article https://ieeexplore.ieee.org/document/7546717. This particle is on thermal noise over power splitter. It has pointed out that on the outputs of a Y shaped 2-R splitter, thermal noise is anti-correlated, meaning they will have different phase.
In the case of white noise and other types of random noise, due to their random nature, they are uncorrelated with anything. Therefore, after they passed through a splitter, they won't be cancelled in a phase reversal or in a phase detector.
I bet if you hook up a good white noise generator to your tester, you will never be able to null it out.