Master Thread: Are Measurements Everything or Nothing?

[antcollinet]

0.0006% vs 0.0003%

The former is still double the voltage (and hence SPL) of the other, and hence four times the power. I'd disagree that it is more difficult to see the difference when expressed as a percent rather than dB (as long as one understands the units used). Though I agree that both figures are inaudible.

 

[danadam]

The former is still double the voltage (and hence SPL) of the other, and hence four times the power. I'd disagree that it is more difficult to see the difference when expressed as a percent rather than dB (as long as one understands the units used). Though I agree that both figures are inaudible.

When you get blurry vision from the amount of zeros then it's good enough

I'd say that that if you have both % numbers aligned one under the other, then it's easy. A bit more difficult when they are next to each other in a single line and more difficult still, when they are in separate places altogether.

 

[MattHooper]

Or is that just sales patter to justify his poor measurements?

I believe Pass has designed both amplifiers that are neutral and transparent, as well as as a certain class of amplifiers that add the bit of distortion. So I think he’s quite capable of designing a solid state amplifier that is neutral. I mean at this stage is pretty darn easy and I would find it implausible that Pass couldn’t turn out a standard solid state amplifier if he wanted to.

ETA: apparently Pass designed the old
Adcom GFA-555 (a neutral amp). And some of his amps measured in Stereophile have being effectively neutral and transparent.

 

[Jiraya369]

The tests I believe would tend to find that nobody can hear any difference at all between any reasonable DAC when listening to music materials. In a world where 90% of DACs are 90 dB+ SINAD, this means essentially all of them. If there is bo difference there can be no preference.

well my wallet would like to introduce a difference to you!

 

[rdenney]

SINAD=signal over noise and distortion—I’ve seen it as S/NAD—and expressed logarithmically in dB.

THD+N=total harmonic distortion plus noise, expressed linearly as a percentage of the signal.

In practice, both are the same. The percentage reveals how similar small values are, and the dB scale spreads those differences out, but that’s just a difference in scaling, and THD+N is also often enough expressed in dB. Usefulness depends on the thresholds one sets no matter what scaling is used.

Rick “-20 dB = 10%, -40 dB = 1%, etc.” Denney

 

[drewdawg999]

SINAD=signal over noise and distortion—I’ve seen it as S/NAD—and expressed logarithmically in dB.

THD+N=total harmonic distortion plus noise, expressed linearly as a percentage of the signal.

In practice, both are the same. The percentage reveals how similar small values are, and the dB scale spreads those differences out, but that’s just a difference in scaling, and THD+N is also often enough expressed in dB. Usefulness depends on the thresholds one sets no matter what scaling is used.

Rick “-20 dB = 10%, -40 dB = 1%, etc.” Denney

I believe Amir has set a threshold for audibility at 115dB SINAD. That seems awful high to me, perhaps it pertains to sine waves, not music. For busyish music I think a SINAD of 30dB could be the threshold of acceptance for most. There's audibility and then there's whether distortion + noise bothers you and takes away from listening pleasure.

 

[Sal1950]

I don't think so. He's long past the point where he can do what he wants - just his name will sell product. I think he believes it.

I find the current situation with Mr Pass a bit disturbing.
He is a brilliant designer that has turned his reputation into a machine for milking the high-end of big bucks. From his ultra expensive Pass Labs gear to the First Watt stuff most is geared to make a statement beyond just accurate reproduction. Instead meant to touch the search for magic in the audiophool community and line his pockets with cash.

 

[solderdude]

There are plenty of designers fully believing their own theories.
Psycho-acoustics does the rest.

Whenever they find out 'the truth' they might have to stick with their theories and keep customers happy while knowing better anyway.
So I suspect that there are some 'audiophile' designers that know they are selling porkies but figure a number of them are still peddling nonsense without even knowing it. Simply because they are human and fall in the same (audio)traps as their customers.

There is plenty of examples in audio where myths are perpetuated and money is made. Many of them have reached fame in audio-lala-land.
It's how the audio industry works.
Fortunately there are also still manufacturers that make good quality gear and do not resort to such practices.

 

[Mart68]

I find the current situation with Mr Pass a bit disturbing.
He is a brilliant designer that has turned his reputation into a machine for milking the high-end of big bucks. From his ultra expensive Pass Labs gear to the First Watt stuff most is geared to make a statement beyond just accurate reproduction. Instead meant to touch the search for magic in the audiophool community and line his pockets with cash.

I have a pal who uses a Pass pre-power, I really enjoy listening to his system so whatever the Pass amplification does, it doesn't do it badly. Looks pretty good too. Yes, expensive, but he can afford it.

 

[JSmith]

Psychoacoustics does the rest.

Indeed... hopefully though there are no psycho acousticians in the mix.


JSmith

 

[antcollinet]

I believe Amir has set a threshold for audibility at 115dB SINAD. That seems awful high to me,

That is an absolute threshold - for all people (including trained 16 year olds, who have never been to a concert without hearing protection) under all circumstances (including sound proofed listening rooms while using headphones, under test conditions)

For the vast majority of people in real world listening conditions - it will be much lower than that. Something of the order of the "Lenient" thresholds here:

Audibility thresholds of amp and DAC measurements

Introduction A recurring theme on ASR is whether or not the various measured qualities of the devices are audible. In this post, I'll present some clear and visual thresholds for when those imperfections can be considered a potentially audible concern. I will not explain the basics of amp/DAC...

www.audiosciencereview.com

Recap of thresholds
Lenient
Dynamic range, linearity: 96 dB
THD, IMD: -66 dBFS / 0.05%
Noise: -85 dBFS / 0.005%
SINAD: 85 dB
Crosstalk: -60 dBFS
Jitter: -110 dBFS, -100 dBFS around the main tone
Frequency response: ±0.5 dB
Channel balance: 1 dB
Output impedance: 2 ohms

Strict
Dynamic range, linearity, SINAD: 120 dB
THD, IMD, noise, crosstalk, jitter: -120 dBFS / 0.0001%
Frequency response, channel balance: ±0.1 dB
Output impedance: 0.16 ohms

There's audibility and then there's whether distortion + noise bothers you and takes away from listening pleasure.

Exactly.

 

[Newman]

I believe Amir has set a threshold for audibility at 115dB SINAD. That seems awful high to me…

IIRC it combines several optimistic assumptions and adds a safety margin.

A DBT of the type of distortion commonly found in amplifiers, playing music, involving a representative population of participants, would IMO probably yield a 95% confidence level of inaudibility at a quite low SINAD. And if noise is removed and only distortion is tested, even lower.

cheers

 

[rdenney]

I believe Amir has set a threshold for audibility at 115dB SINAD. That seems awful high to me, perhaps it pertains to sine waves, not music. For busyish music I think a SINAD of 30dB could be the threshold of acceptance for most. There's audibility and then there's whether distortion + noise bothers you and takes away from listening pleasure.

Amir’s threshold is the absolute one—the one where nobody can argue from any perspective that the distortion is detectable no matter what special listening techniques they employ. And it’s for source devices that will be subsequently amplified.

But for listening to music in a real setting, especially with loudspeakers, the threshold is far lower. I seriously doubt anyone could distinguish two DACs if both are better than 96 dB SINAD (16-bit Redbook CD theoretical quality), at least without training in special listening techniques such as gain-riding the quiet bits. We’ve already seen tests where listeners can’t distinguish between 16/44.1 Redbook and 24/96. And with amps, I’d put that threshold closer to 70 dB. Even there, one has to crank a system to very loud for that distortion+noise level to be even within 10 dB of most residential ambient noise levels, though the specific noise frequencies do matter.

Even these are demanding thresholds. When playing music, my ability to distinguish added distortion is tested to be in the upper 30’s, but then I’m old.

Edit: I see ant got there first

Rick “air and ears distort, too” Denney

 

[Mnyb]

Noise is the most obvious factor depending on your gain structure and speaker sensitivity , it can matter ?

 

[rdenney]

Noise is the most obvious factor depending on your gain structure and speaker sensitivity , it can matter ?

Yes, but for me it’s only quiescent hiss. If I have to put my ear to the tweeter to hear it, I don’t much care, but for me it’s worth some effort to eliminate from normal distances.

If it’s 100 dB down, and the amp with no attenuation is capable of 25 dB gain, a broad-band noise signal might reach audible, especially up close.

Rick “likes the Holman preamp which does not amplify noise unless the volume is turned up” Denney

 

[Sal1950]

I have a pal who uses a Pass pre-power, I really enjoy listening to his system so whatever the Pass amplification does, it doesn't do it badly. Looks pretty good too. Yes, expensive, but he can afford it.

I'm sure the system sounds impressive, specially if the speakers were well chosen at a cost level equal to the Pass electronics.
I just find it sad that Nelson no longer lends his expertise to a mid-fi company like Adcom with the goal of offering accurate gear at affordable prices.
The 5 Adcom amps from the 1990s I'm using here still perform admirably.

 

[RDoc]

Floyd Toole et al have done great work characterizing what measurements are perceived and being liked by listeners.

Amplifiers and the rest of the electrical chain are rated by SINAD, noise plus distortion irrespective of harmonic order. But, listeners are not linearly sensitive to harmonic distortion since we are much more sensitive to higher harmonics. This is the basis of some of the other measures such as GedLee and Shorter-Mason.

I'm solidly in the measurements camp as opposed to the golden ears camp, but I'm beginning to question the use of SINAD. GedLee weights the effects of harmonics above 5 or so very heavily and it has been shown to be valid in listener tests. Depending on the higher harmonics, two amps rated at 85 SINAD could have very different GedLee metrics and likely would have different perceived "quality". Particularly for class D amps, there tend to be quite a lot of higher order harmonics whose full effects on listening aren't captured by SINAD.

 

[voodooless]

Floyd Toole et al have done great work characterizing what measurements are perceived and being liked by listeners.

Amplifiers and the rest of the electrical chain are rated by SINAD, noise plus distortion irrespective of harmonic order. But, listeners are not linearly sensitive to harmonic distortion since we are much more sensitive to higher harmonics. This is the basis of some of the other measures such as GedLee and Shorter-Mason.

I'm solidly in the measurements camp as opposed to the golden ears camp, but I'm beginning to question the use of SINAD. GedLee weights the effects of harmonics above 5 or so very heavily and it has been shown to be valid in listener tests. Depending on the higher harmonics, two amps rated at 85 SINAD could have very different GedLee metrics and likely would have different perceived "quality". Particularly for class D amps, there tend to be quite a lot of higher order harmonics whose full effects on listening aren't captured by SINAD.

SINAD isn’t a perceptual model, and it doesn’t need to be.

Once all distortion components are below audibility, changing the weighting doesn’t make them audible again.

As to higher order Class D distortion: where?

Do I need to go on?

 

[ahofer]

I'm sure the system sounds impressive, specially if the speakers were well chosen at a cost level equal to the Pass electronics.
I just find it sad that Nelson no longer lends his expertise to a mid-fi company like Adcom with the goal of offering accurate gear at affordable prices.
The 5 Adcom amps from the 1990s I'm using here still perform admirably.

My Adcoms were great, and at the time, the 5802 was a great watts/$ solution for my brutal Thiel cs3.6 speakers. But holy crap was it hot, and had to be recapped a couple of times.

 

[danadam]

I believe Amir has set a threshold for audibility at 115dB SINAD. That seems awful high to me, perhaps it pertains to sine waves, not music. For busyish music I think a SINAD of 30dB could be the threshold of acceptance for most.

There's no distinction in the SINAD number between noise and distortion. I'm guessing that the 115 dB threshold is for the worst case scenario, where it is the noise that dominates. And you have a quiet room and your volume is set to listen highly dynamic material very loud, in which case you could maybe hear the noise when nothing plays if the SINAD was lower than 115.