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Misleading Measurements


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2 hours ago, Audiophile Neuroscience said:

I don't trust Amir's measurements.

 

Not completely sure its relevant here but Amir misappropriated ADI's measurements of their DAC chip to malign Schiit. If you need a link I'll look it up.

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1 hour ago, Audiophile Neuroscience said:

Thanks, as an example of "misleading measurements" and biased reporting rendering agenda-based measurements meaningless.ūüėÉ

 

This post is indeed a prime example of misleading measurements. You need to go to the AD5547 datasheet to see why though, the small print gives away that the two FFTs Amir places side by side are not comparable.

 

https://www.audio ‚Äúscience‚ÄĚ review/forum/index.php?threads/review-battle-of-schiit-audio-dacs.5487/post-121858

 

Seems someone doesn't want a link pointing to ASR, you need to get rid of those quote marks, close up the spaces and add .com before it becomes valid.

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The key insight is that the AD5547 is a multiplying DAC and this FFT shows it operating in that mode - with its reference voltage being fed a sinewave. So the digital input is being held constant, unlike in the FFT on the right.

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4 hours ago, pkane2001 said:


Well, not all, as the JDS Labs Atom in the review showed no difference with filtered and unfiltered power, and Amir’s power line is pretty dirty.

 

Let me guess - no common-mode measurements were made in that review?

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Because a significant amount of power line noise is common-mode.

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Normally power line filters have elements to filter common-mode noise (a CM choke for example) as well as normal mode noise (LC filtering perhaps). Wouldn't comprehensive measurements wish to characterize both?

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2 hours ago, pkane2001 said:


Maybe. But if the power line carries a lot of common mode noise as you say, Amir’s test would show the combination of what the filter did to both, normal and common mode noise. To me that’s what matters in the end: does the filter eliminate noise, and if it does, does this have an effect on the output of my audio system.

 

I'd also presume readers would want to know what the filter did to both. But separate, distinct measurement setups are required for each which is why I guessed Amir hadn't made the CM measurements. I've not read the review - am I wrong in my guess?

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11 hours ago, pkane2001 said:

 

Don't know enough about CE certification, but my impression is that it has to do with noise produced/emitted by a component rather than noise filtration of already dirty power. Is this not correct?

 

EM emissions are a part of it, another part is EMC susceptibility. Susceptibility testing looks to see that the product continues to work (subject to certain defined levels of degradation) in the presence of EM aggressors.

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9 hours ago, Ajax said:

My experience has been that you will never convince any of these guys that they need measurements because they have the potential to undermine "their" hobby.

 

Measurements are analogous to the grammar of audio. Try convincing someone you met in the East End of London with a Cockney drawl that he needs grammar. What he has works for him, why bother him with grammar?

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2 minutes ago, Clockmeister said:

Indeed in similar fashion you could argue you same for southern states hick's 'When we having possum Ma?' or UK West Country bumpkins with 'My luvver' similar situation I suspect.

 

Yes. The precise instantiation is immaterial.

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1 minute ago, pkane2001 said:

 

Distortions between channels: crosstalk, level imbalance/nonlinearity, phase.

 

How have you determined that its these?

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1 minute ago, pkane2001 said:

Crosstalk is easy. Level imbalance is easy. Phase differences using DeltaWave, but other tools that show phase will do this, like REW.

 

You've lost me so let me backtrack.

 

Let's begin with your first one which was 'distortions between channels'. I'm unclear what that means - even though I'm pretty clear on distortion itself. Soundstage is going to get flatter if one channel has more distortion than the other?

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1 minute ago, Audiophile Neuroscience said:

says who? where is your evidence?

 

I tend to concur with @pkane2001 on this - soundstage depends on the whole system not just the DAC. Which is why it won't be quantified by just measuring the DAC in isolation.

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Just now, pkane2001 said:

 

Differences between time of arrival and amplitude between the two channels will cause a change to soundstage, as will crosstalk. 

 

You've quantified this (the former) with your software? Does Amir make measurements of differences in time of arrival between channels for DACs? I must confess I've not seen any but I'm an infrequent visitor to ASR.

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4 minutes ago, pkane2001 said:

 

Amir usually measures channel imbalance and crosstalk. Don't think he's measured phase differences before, but I could be wrong. 

 

So on your first cited measurement, its not one that's currently at all popular? If that's true then it won't help me pick a DAC which doesn't flatten the soundstage ISTM.

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