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General debate thread about audio measurements

josh358

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A very strange idea - it implies that bits are not just bits, and that there are variations in the "quality" of bits in the digital domain. I am not an engineer, but I thought bits are bits, and nothing more. (Unless pit geometry flaws lead to missing bits, e.g. lost information to the extent that error correction cannot recover it.)
This is one of the things that surprised us in the early days of digital audio, when we assumed as you do that bits are just bits. The problem turned out to be jitter, which was passed on to the converters. Today, we go to lengths to minimize it. That's why you'll see jitter in DAC measurements.
 

josh358

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Josh should try the Blumlein's 8th ADC/DAC copy challenge, don't click on "Spoiler" until you have the results.

https://www.audiosciencereview.com/...-choose-the-8th-generation-digital-copy.6827/
Heh, fun, I listened to three and wasn't able to hear the difference. So he did better than I did, it seems he was able to ABX them. It would have been more interesting with more demanding program material, I don't know how to judge anything with tracks like this. But I've heard this done with even more round trips, and it's amazing how little the sound changes!
 

gvl

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Heh, fun, I listened to three and wasn't able to hear the difference. So he did better than I did, it seems he was able to ABX them. It would have been more interesting with more demanding program material, I don't know how to judge anything with tracks like this. But I've heard this done with even more round trips, and it's amazing how little the sound changes!

Considering this, what can we say about under-damped ESS filters then? The DAC he used is based on the 9038 mobile chip, and this DAC has the "glare" in my book, yet the 8th copy is basically indistinguishable by most.
 

josh358

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Considering this, what can we say about under-damped ESS filters then? The DAC he used is based on the 9038 mobile chip, and this DAC has the "glare" in my book, yet the 8th copy is basically indistinguishable by most.
I wouldn't hear the glare on this program material, indeed, the 9038Pro sounded amazing to me on small ensembles and notes of short duration. Try something like massed violins, orchestra. This is where equipment generally runs into trouble, and where the ear has a good acoustical reference, which is why IIRC the Harman research found that orchestral recordings were the most effective for the evaluation of loudspeakers.

I'm also not sure where the "glare" comes from. It certainly isn't a response aberration, these DAC's measure flat. But it sounds like a massive one. Very frequency dependent. Perhaps the overshoot, as the guys at Emotiva believe.

Of course there's another possibility, which is that the ESS DAC's are right and it's the Gungnir that's wrong . . . it would be interesting to try this experiment with better program material and both DAC's to assess that. And measurements of impulse response would be interesting too. As I recall, the interview in which the guy from ESS mentioned this had a plot of the impulse response, but I did a search and couldn't find the article -- if anyone remembers more details that would be great.
 

edechamps

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IIRC the Harman research found that orchestral recordings were the most effective for the evaluation of loudspeakers

No it didn't. Authors affiliated with Harman (primarily Sean Olive) determined that certain pop music tracks were most effective at producing the most discriminating results in loudspeaker evaluation, and that's what they use when they do blind preference testing on loudspeakers. For example, Olive's paper that I previously mentioned previously states:

Sean Olive said:
The [following] programs were selected on the basis of their ability to reveal spectral and preferential differences between different loudspeakers in over 100 different listening tests and various listener training exercises.
- James Taylor, “That’s Why I’m Here” from “That’s Why I’m Here,” Sony Records.
- Little Feat, ”Hangin’ On to the Good Times” from “Let it Roll,” Warner Brothers.
- Tracy Chapman, ”Fast Car” from “Tracy Chapman,” Elektra/Asylum Records.
- Jennifer Warnes, “Bird on a Wire” from “Famous Blue Rain Coat,” Attic Records.
 

LTig

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This is one of the things that surprised us in the early days of digital audio, when we assumed as you do that bits are just bits. The problem turned out to be jitter, which was passed on to the converters. Today, we go to lengths to minimize it. That's why you'll see jitter in DAC measurements.
In the case of the CD-player you mentioned above Jitter is no problem, because the clock of the DAC controls the data stream of the drive and not the other way (when a CD drive feeds an external DAC via SPDIF). Therefore I see no way how the pits on the CD can influence the final audiostream as long as they are detected at all.

A side note: A month ago I witnessed a demo of an extremly expensive CD (made of glass, € 2000.-, don't you ever let it drop :facepalm:) compared to the standard CD. Both were identical WRT the bit content. I could here no difference. Afterwards I asked whether it wouldn't make more sense to rip the standard CD and play it from disc to circumvent any problems with CD drives. The answer was that ripping has its own problems ...:facepalm:
 

March Audio

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This is something I do not understand, at least not as long as I think that I know how a CD-player works internally.

It's not an issue. Reading errors are inherent. The Reed Solomon error correction recovers the data where it can't be successfully read. Any remainig error will be very short and concealment or muting and possibly an obvious click will occur if its very bad. The fundamental "sound" quality will absolutely not change.
 
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LTig

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It's not an issue. Reading errors are inherent. The Reed Solomon error correction recovers the data where it can't be successfully read. Any remainig error will be very short and concealment or muting and possibly an obvious click will occur if its very bad. The "sound" quality will absolutely not change.
Yep, that's the current state of my understanding as well.
 

March Audio

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In the case of the CD-player you mentioned above Jitter is no problem, because the clock of the DAC controls the data stream of the drive and not the other way (when a CD drive feeds an external DAC via SPDIF). Therefore I see no way how the pits on the CD can influence the final audiostream as long as they are detected at all.

A side note: A month ago I witnessed a demo of an extremly expensive CD (made of glass, € 2000.-, don't you ever let it drop :facepalm:) compared to the standard CD. Both were identical WRT the bit content. I could here no difference. Afterwards I asked whether it wouldn't make more sense to rip the standard CD and play it from disc to circumvent any problems with CD drives. The answer was that ripping has its own problems ...:facepalm:
Correct. As you say its determined by the dac clock. The audio word data received by the dac has been buffered and error corrected. There appears to be a bag full of Audiophile myths that are being pulled out one by one ;)
 
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amirm

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In the case of the CD-player you mentioned above Jitter is no problem, because the clock of the DAC controls the data stream of the drive and not the other way (when a CD drive feeds an external DAC via SPDIF).
This only happens in players that use data drives (e.g. Meridian CD players of old). The classic solution was to extract the clock from the incoming stream:

1558903191911.png
 

g29

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... Ahh yes, the ultimate reverse UNO card. My system is more revealing.

@Veri , different systems are different by definition of being different. How's that for circular logic !!!

I had a pair of high efficiency 101dB 8-Ohm horns in the 80's and an amp combo that you could plainly hear constant noise when paired. Pairing the same amp with average efficiency speakers of @ 92dB or less, the noise was not appearant. Pairing the high efficiency horns with a different amp the noise was not apparent.

The high efficiency horns either revealed/highlighted something the other speakers masked or the amp irritated something in the high efficiency horns that it did not irritate in the average efficiency speakers.

I did not have the means to measure/identify the specific problem so I can't attribute the cause to the amp, the horns, something upstream being passed/blocked or combination thereof, but what ever it was, there was an obvious audible noise level difference between the 2 pairings.
 
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March Audio

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This only happens in players that use data drives (e.g. Meridian CD players of old). The classic solution was to extract the clock from the incoming stream:

View attachment 26727
However the dac clock is not directly related to the disc derived signal as implied elsewhere. The disc speed varies from outer to inner to account for linear velocity, it also continually accelerates and decelerates to prevent FIFO buffer under / over runs. This variation would end up directly represented in the dac output if it were directly related to the disc clock signal. In your diagram the sync detect timing block and clock feeds ic8 which is?
 
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mansr

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This only happens in players that use data drives (e.g. Meridian CD players of old). The classic solution was to extract the clock from the incoming stream:

View attachment 26727
See that crystal at the top right? That's the master clock. The "turntable motor servo-amp" at the bottom right adjusts the rotational speed of the disc to provide the correct data rate. A FIFO buffer somewhere in the chain absorbs the inevitable variations in the raw signal rate.
 

March Audio

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@Veri , different systems are different by definition of being different. How's that for circular logic !!!

I had a pair of high efficiency 101dB 8-Ohm horns in the 80's and an amp combo that you could plainly hear constant noise when paired. Pairing the same amp with average efficiency speakers of @ 92dB or less, the noise was not appearant. Pairing the high efficiency horns with a different amp the noise was not apparent.

The high efficiency horns either revealed/highlighted something the other speakers masked or the amp irritated something in the high efficiency horns that it did not irritate in the average efficiency speakers.

I did not have the means to measure/identify the specific problem so I can't attribute the cause to the amp, the horns, something upstream being passed/blocked or combination thereof, but what ever it was, there was an obvious audible noise level difference between the 2 pairings.
I'm not sure that's an appropriate example. All amps have noise. The high sensitivity of the horns just means it was loud enough to be noticed. When playing music with a normal sensitivity speaker you would turn the amp up louder to reach the same listening volume as with the horns. All other things being equal it would be no less transparent.

I suppose If anything you could argue that the horns create a problem and the increased apparent noise floor could mask very low level sounds.
 

g29

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I'm not sure that's an appropriate example. All amps have noise. The high sensitivity of the horns just means it was loud enough to be noticed. When playing music with a normal sensitivity speaker you would turn the amp up louder to reach the same listening volume as with the horns. All other things being equal it would be no less transparent.

I suppose If anything you could argue that the horns create a problem and the increased apparent noise floor could mask very low level sounds.

Listening at the same SPL, it was audible on the horns and not on the average efficiency speakers.
Listening with a different amp at the same SPL, it was not audible on the horns (or other speakers).

I would love to have seen the measurements between the two amps and their respective power output levels (assuming @ 9dB difference in volume settings).

On the bright side, I repurposed the "noisy" amp to the rear speakers and added a new amp for the fronts. Problem pairing circumvented.
 

g29

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I'm not sure that's an appropriate example. All amps have noise. The high sensitivity of the horns just means it was loud enough to be noticed. When playing music with a normal sensitivity speaker you would turn the amp up louder to reach the same listening volume as with the horns. All other things being equal it would be no less transparent.

I suppose If anything you could argue that the horns create a problem and the increased apparent noise floor could mask very low level sounds.

I always thought amp noise/distortion goes up with volume/load (but NOT in the case of the Benchmark).

If the that trend held true for 80's amps, one would think the noise would have been more audible on average efficiency speakers (assuming same resolution between efficient and average efficiency) because the volume setting would be @ 9dB higher on the average efficiency speakers ???
 

March Audio

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Don't misunderstand me, one amp is clearly more noisy than the other. However the horns high sensitivity creates the problem. The noise is inaudible with normal speakers and not a problem.

So yes circumstance can create issues, but you can't say that particular noisier amp is less revealing when used in appropriate circumstances.
 
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March Audio

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I always thought amp noise/distortion goes up with volume/load (but NOT in the case of the Benchmark).

If the that trend held true for 80's amps, one would think the noise would have been more audible on average efficiency speakers (assuming same resolution between efficient and average efficiency) because the volume would be @ 9dB higher ???

Its not that simple.if you look at the SINAD plots they fall until such point that distortion really starts to climb.
 

LTig

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I always thought amp noise/distortion goes up with volume/load (but NOT in the case of the Benchmark).
Distortion goes up with volume. The noise though is fix and depends (if at all) only on the impedance of the feeding source. There may be a rare case of a power amp whose volume controls the feedback loop and then the noise may increase with volume.
 
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