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Old 10-11-2018, 02:32 PM   #15
wwenze
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Can we compare device measurements like that? What variables do we need to be mindful of? Different tester conditions and equipments?
Yes and no, easier to point things out as we go along. Measurements are only valid for that particular set up, but this also means if another person has the same set up, he is bound to get the same results. This is why you see people measure different setting conditions, some even doing multiple shmoos of graphs.

For example, the Dragonfly's measured crosstalk is better than the SXFi's:
http://archimago.blogspot.com/2017/0...black.html?m=1
I don't see Archimago saying he used 16 ohm or whatever ohm load with the DF Black anywhere. So the results are not comparable. However, I do have the unloaded measurements of SXFi. The Dragonfly's crosstalk is worse, since it measures at -71.5dB unloaded while SXFi measures at -75.6dB.

However both are simply mediocre compared to the rest in this chart.



And usually crosstalk just gets worse with load. If the Dragonfly is losing to SXFi unloaded, it is likely to also lose to it when loaded.

Is the reduction of crosstalk a matter of additional circuitry? Or better quality components? Maybe that's a tradeoff Creative did to keep the amp smaller? Or cheaper to improve the profit margin, given the focus is on the SXFi mode.
Crosstalk is usually due to weak power supply, particularly the ground. Better ground routing and more filtering tends to help. This results in an increase in size.

However, the SMSL iDEA is also small, yet has crosstalk at the same level as others.

https://archimago.blogspot.com/2017/...a-usb-dac.html

Plus the SMSL iDEA's noise is also better than the rest, while SXFi's noise is worse than the thing it is connected to. Again, weak power supply. Or rather, weak power supply noise rejection too.

This reminds me of the case of higher-performing IC vs lower-performing IC. The LM4562 vs NE5532 is an example. LM4562 gets higher performance, but if you just throw it into a circuit that uses NE5532, you end up with more noise. If you throw a fast digital circuit e.g. DAC without sufficient decoupling, you end up with more noise too.

And this is what I believe is happening with SXFi and AK4377. A high-performing DAC was chosen for the good distortion numbers, but higher noise as a result. The overall result is actually worse than if a lower-performing DAC were to be used, as explained in post #13. This doesn't change the fact that the numbers look amazing on marketing material, regardless of practical performance. And I feel this is what they are aiming for.

While part cost does matter, looking at how SMSL iDEA is doing, the problem is probably design. And/or profit margin.
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