Misleading Measurements

[pkane2001]

3 minutes ago, fas42 said:

 

Of course it can be measured ... but no-one actually does it ... give me a single link, to any online document, that has a specific measure of a particular component's performance in this one thing - no, "part of the overall picture" stuff, please!

 

I usually measure a component with a 60Hz (regular US mains frequency) and at 70Hz. If there’s any mains dependency in the component, it will show up as a frequency difference in the spurious tones in an FFT, or a change in the noise floor.

[fas42]

37 minutes ago, pkane2001 said:

 

I usually measure a component with a 60Hz (regular US mains frequency) and at 70Hz. If there’s any mains dependency in the component, it will show up as a frequency difference in the spurious tones in an FFT, or a change in the noise floor.

 

Which is not measuring what I'm talking about - one way, out of many possible, of determining what I consider important is to inject a sweep of frequencies, starting from the mains frequency, to the mains plug of the component while it is powered up, and monitoring what happens to the noise spectrum.

[pkane2001]

3 minutes ago, fas42 said:

 

Which is not measuring what I'm talking about - one way, out of many possible, of determining what I consider important is to inject a sweep of frequencies, starting from the mains frequency, to the mains plug of the component while it is powered up, and monitoring what happens to the noise spectrum.

It’s easier to just compare a component plugged into a wall outlet to one plugged into a power regenerator that has none of the junk. 

[fas42]

28 minutes ago, pkane2001 said:

It’s easier to just compare a component plugged into a wall outlet to one plugged into a power regenerator that has none of the junk. 

 

And who has posted details of what they've found?

[sandyk]

1 hour ago, pkane2001 said:

 

Really? Mains interference is never measured? Maybe it's not something a THD or SINAD number by itself will reveal, but certainly distortion and noise floor plots will show it.

 

 

 These measurements are normally taken with the D.U.T. under isolated conditions, not as  part of a system

[Audiophile Neuroscience]

7 hours ago, manisandher said:

Yep. The two inputs were measured as being bit-identical. There seemed to be no consistent differences in the analogue outputs (admittedly with a non-SOTA ADC it transpired)... and yet... I could hear a difference.

 

Is it that our threshold of audibility is below the level to which we can measure THD/SINAD, etc., or... are we simply measuring the wrong things?

 

Hi Mani. I believe both. What is needed is an open minded scientific approach to the problem ('from first principles' 😀) which recognizes audio measurements clearly do not provide the full picture in sound perception. I think with experiments like your "Red/Blue Pill" and with 'switched on engineers' guided by science (not dogma) there is hope.

 

As example of a good engineer IMO Mallinson of former Sabre DAC CTO fame, and now with his own company, reported blind tests involving the 9018 chip "hyperstreaming" technology whereby human perception was below what was then deemed the threshold of audibility and ability to hear signals much lower than the SNR of many audio equipment, and at least 120 to 130 dB.

 

He stated "I have to admit that people can [hear] and when you admit that people can and you enter a scientific process of saying that well clearly they are hearing something that the instrumentation is not measuring." He was referring to non-uniform noise later described as non-periodic steady-state noise . He noted this kind of noise is not seen using measurements in the steady state  such as THD, SNR or DNR. It was better seen by looking at the effect on DC offset .

 

He explained that resonator in the human ear has a noise bandwidth very much less than the Nyquist bandwidth of the system. He attributed this to what he referred to a feedback loop from brain to a "little muscle" attached to cochlear hair cells. He was of course referring to  the well-known electromotile amplifier response of the outer hair cells of the cochlea.

[pkane2001]

16 minutes ago, fas42 said:

 

And who has posted details of what they've found?

I have, and I’ve seen Amir post comparisons with a laboratory power supply with regeneration vs. just a wall outlet.
 

When testing one of the audiophile power supplies, I recommended to him  to use the 70Hz trick and he confirmed that the supply was leaking that frequency from its own power line.

[pkane2001]

.

[Audiophile Neuroscience]

1 minute ago, pkane2001 said:

I’ve seen Amir post comparisons

I don't trust Amir's measurements. They would need to be reproduced.

[fas42]

6 minutes ago, pkane2001 said:

I have, and I’ve seen Amir post comparisons with a laboratory power supply with regeneration vs. just a wall outlet.
 

When testing one of the audiophile power supplies, I recommended to him  to use the 70Hz trick and he confirmed that the supply was leaking that frequency from its own power line.

 

Any links?

[pkane2001]

1 minute ago, Audiophile Neuroscience said:

I don't trust Amir's measurements. They would need to be reproduced.

That’s  your prerogative, of course. Many of his measurements have been reproduced by others, including amateurs and manufacturers. While I’d certainly like to see more people posting the same measurements for verification, I’m not suspicious of his results.

[pkane2001]

6 minutes ago, fas42 said:

 

Any links?

These shouldn’t be hard to find, just look for his reviews that mention lab power supply 

[fas42]

First thing I found was a post by Amir, where he said,

 

Quote

I actually have one of the old PS Audio regenerators. I measured it once and it is as clean as my Lab AC generator. So it does what it says but again, won't make a difference in the analog output of the audio product.

 

So, he has the assurance of knowing how all audio components behave, without even measuring ... 😉.

[pkane2001]

11 minutes ago, fas42 said:

First thing I found was a post by Amir, where he said,

 

 

So, he has the assurance of knowing how all audio components behave, without even measuring ... 😉.

Keep looking  I also have one of the old PS Audio regenerators. The cool thing about it the ability to switch the mains frequency.

[fas42]

Okay, bit of detective work later, he's using a BK Precision 9801 AC generator - hmmm, I would be much happier if it were a 9833 model - 3,000VA versus 300 for the 9801. ... But, a decent start, 🙂.

[fas42]

And, the very thing that would be useful, which would to introduce higher harmonics, to make things interesting, is missing... looking around, one company that's producing meaty products getting much closer to being fully versatile is Chroma, http://www.chromaate.com/product/Regenerative_Grid_Simulator_61809_61812_61815.htm

 

[Audiophile Neuroscience]

1 hour ago, pkane2001 said:

That’s  your prerogative, of course. Many of his measurements have been reproduced by others, including amateurs and manufacturers. While I’d certainly like to see more people posting the same measurements for verification, I’m not suspicious of his results.

 

and that's your prerogative but you must realize that citing his measurements may be only convincing to the disciples. If those measurements have been verified it would be useful to specify this IF your aim is to convince others. It is otherwise just noise.

[pkane2001]

3 minutes ago, Audiophile Neuroscience said:

 

and that's your prerogative but you must realize that citing his measurements may be only convincing to the disciples. If those measurements have been verified it would be useful to specify this IF your aim is to convince others. It is otherwise just noise.

 

Not sure I get your point. For me, verifying measurements is part of an objective process of validating results, and not part of convincing the heathen. This is not a religious pursuit and not an act of faith, it's a simple process of confirming engineering findings.

[Audiophile Neuroscience]

1 minute ago, pkane2001 said:

 

Not sure I get your point. For me, verifying measurements is part of an objective process of validating results, and not part of convincing the heathen. This is not a religious pursuit and not an act of faith, it's a simple process of confirming engineering findings.

My point is simple. If Amir's measurements are not trusted except by his disciples then the disciples are the only ones you will convince (without adding the verification)

[pkane2001]

Just now, Audiophile Neuroscience said:

My point is simple. If Amir's measurements are not trusted except by his disciples then the disciples are the only ones you will convince (without adding the verification)

 

So my statement that his measurements have been verified by independent parties means that the measurements can be trusted by more than his disciples, or am I still misunderstanding?

 

[opus101]

1 hour ago, fas42 said:

So, he has the assurance of knowing how all audio components behave, without even measuring ... 😉.

 

As far as I recall, Amir is clueless about common-mode noise. I did try to educate him once when he was still active on WBF but he proved singularly resistant.

[fas42]

Another interesting bundle of thoughts I just came across, when someone asked for some noise making ideas ... https://www.eevblog.com/forum/projects/intentionally-injecting-noise-into-supply-rails/

 

 

[Audiophile Neuroscience]

5 minutes ago, pkane2001 said:

 

So my statement that his measurements have been verified by independent parties means that the measurements can be trusted by more than his disciples, or am I still misunderstanding?

 

 

"his measurements" - do you mean all?

 

If referring to "I [you] have, and I’ve seen Amir post comparisons with a laboratory power supply with regeneration vs. just a wall outlet."

 

Then that is fine if you mean you have verified Amir's comparisons with a laboratory power supply with regeneration vs. just a wall outlet

 

 

 

[pkane2001]

11 minutes ago, Audiophile Neuroscience said:

 

"his measurements" - do you mean all?

 

If referring to "I [you] have, and I’ve seen Amir post comparisons with a laboratory power supply with regeneration vs. just a wall outlet."

 

Then that is fine if you mean you have verified Amir's comparisons with a laboratory power supply with regeneration vs. just a wall outlet

 

🤪 I need a drink...

 

[opus101]

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.