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AES Paper Digest: Do Audio Op-amps Sound Different?

oivavoi

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Hahaha :)

I know how to convert THD % to dB but this shoutometer comparison is really giving things a new perspective! Does it have something to do with the real shouting scenario in the otherwise quiet space (mountain for example) or your figures were just for fun?

I absolutely love the shoutometer. But I just realized: when walking in the mountains of Norway, I know from experience that I have no problem at all hearing people shouting from 1 km away. In a residential neighborhood? Probably not. Which means... the shoutometer is probably not completely precise as a measurement scale at the moment! (a shocking realization indeed)
 

Krunok

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I absolutely love the shoutometer. But I just realized: when walking in the mountains of Norway, I know from experience that I have no problem at all hearing people shouting from 1 km away. In a residential neighborhood? Probably not. Which means... the shoutometer is probably not completely precise as a measurement scale at the moment! (a shocking realization indeed)

Interesting.. But you're referring to the situation in which you're only listening to a person shouting from 1km, and that is not the case here.

Here are my thoughts: if playing base tone is equivalent to a person shouting at you from 1 m distance I'm pretty sure I won't be able to hear another person shouting higher harmonics from 1Km as it will combine nicely with the base tone. But the question is would I be able to hear a person shouting noises or other non-harmonic frequencies (say from IM distortion) in addition to the base tone? I somehow doubt it..
 

RayDunzl

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Does it have something to do with the real shouting scenario in the otherwise quiet space (mountain for example) or your figures were just for fun?

Just using the general approximation of six decibel loss (shouter is in free space, no loss due to heating the air along the way, no reflecction off a mountainside, no concentration along the ground due to atmosphereic effects) for a doubling of distance.

I think this is a fair guesstimate, since the actual distance is just "across the room" and the signal level is diminished, you aren't relocating the speaker (Shouter).

It's just an amusing calculation.

I just now lowered my comfortable afternoon listening to Dr John level by 60dB. I can barely hear something if I put my (deaf) ear to the speaker.

Original listening level (C-weighted, except peak, which is unweighted):

upload_2018-4-24_14-3-26.png


Afternoon room "quiet" level (A-weighted) as reported by UMIK-1 and REW

upload_2018-4-24_14-8-5.png


The big number in both displays is Leq - http://www.gracey.co.uk/basics/leq-b1.htm

(maybe actually LCeq and LAeq)

Quiet and listening RTA:

upload_2018-4-24_14-11-31.png upload_2018-4-24_14-12-24.png
 
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Krunok

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Ok, that sounds both, reasonable and amusing to me! :)
And yes, I agree it is a fair guesstimate.

Still, when speaking about the distortion and the noise, I believe we should take into consideration that the base tone is still playing while distortion and noise is being added to it, so it is not quite the same as lowering the base tone to -60dB. Or I'm wrong?
 

RayDunzl

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I believe we should take into consideration that the base tone is still playing while distortion and noise is being added to it, so it is not quite the same as lowering the base tone to -60dB. Or I'm wrong?

You are correct. That subject is "masking".

https://www.google.com/search?source=hp&ei=_XTfWprsIcjYsQWLzL7wDw&q=site:audiosciencereview.com+masking

Amirm and others can give psychoacoustic references to that subject.

I'm just an amateur scientifically bent practical experimenter here at Neverland East.
 

Krunok

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I'm just an amateur scientifically bent practical experimenter here at Neverland East.

Hahahaha - I live in Balkan (Croatia), so for God's sake don't ever think that you live at "Neverland East"! :)

P.S. I agree that Amir is very knowledgeable and that we can fully trust his opinion upon everything except Topping products, as we have established beyond any reasonable doubt that Topping is paying him to promote their products! :D
 
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Arnold Krueger

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Here is their website: http://www.lts.a.se/

It's formally called Ljudtekniska sällskapet, which you could translate as "The society for audio technology" (I've previously translated it as the Swedish Audio Engineering Soceity, but I don't think it's a good translation).

Their measurement reports and listening tests are documented in their printed magazine in Swedish, which is not peer-reviewed, and unfortunately not available online either. But all the testing is run by this guy, who does acoustic and psychoacoustic research for a living: https://www.kth.se/profile/ssg/

In short: There is no reason to rubbish these tests.

Proper scientific skepticism says: "Show me the beef".

Rule of thumb, if you've got something valuable, why keep it under a bushel basket?

All I've seen so far is excuses for past bad behavior (rubbishing the name of the group) and still zero reliable information at all about the alleged tests.

I've been flogging audio DBTs for over 40 years. People trying to obfuscate sighted evaluations into the perception of there was a reliable DBT is one of the older stories around.

It is easier to talk a good test and to actually do one!

In the end, any result seemingly this significant would need to be replicated by an independent party to be really worth talking about.

Since it has been too much of a struggle to just get the proper name of the purportedly responsible parties, nobody should be basking in a sea of confidence.

More information, please!
 

oivavoi

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Hey, what's up with that tone? "Past bad behavior"? If you're truly interested in having a fruitful exchange on the matter, I will kindly ask you to change gear a bit.

That said, I can try and cough up some stills from the magazine article with the Oppo test later this week. I think I still have it lying around somewhere.

Concerning the need for replication: for sure. I do social science for a living, so I know a thing or two about the potential fallacies of experimental testing.
 
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Wombat

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You often see statements like this: "The shortest signal journey can reproduce the best detail and dynamic, and almost without sound coloration ".

This is in my view a somewhat naïve view. Firstly, in the limit, a single device is shortest and fastest, but will almost guaranteed color your sound due to distortions, possibly noise, frequency response deviations. When you take that one device and want to make it more "detail and dynamic, and almost without sound coloration", you need to add devices.....

Secondly, what is the value of a short signal journey at one specific place after a journey through dozens of stages (mostly opamps!) in the recording and mixing console, the tape recording or ADC-CD recorder, the DAC etcetera?

I can well believe that a discrete stage sounds different, under some circumstances, to a competently engineered opamp stage. But different does not mean better by whatever metric.

I have been privy to home recordings, directly through a home-brew opamp mic stage directly into a portable digital recorder. THAT, my friends, is what I would call a short signal journey and what gives you incredible detail, dynamics and uncolored sound.


Travel? Journey?

Propagation: https://www.edn.com/electronics-blo...e-of-Thumb--3-Signal-speed-on-an-interconnect
 

Arnold Krueger

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Hey, what's up with that tone? "Past bad behavior"? If you're truly interested in having a fruitful exchange on the matter, I will kindly ask you to change gear a bit.

That said, I can try and cough up some stills from the magazine article with the Oppo test later this week. I think I still have it lying around somewhere.

Concerning the need for replication: for sure. I do social science for a living, so I know a thing or two about the potential fallacies of experimental testing.


Photographs of magazine pages in a foreign language are pretty useless to me and probably most others who read this forum - we need something that we can use with Google Translate.

I've pushed photographs of text through OCR in my native language, and that has turned out to be very difficult and with limited benefits because of all of the typos. Doing this in a language that I have no familiarity with is pretty much mission impossible.

I've worked with listening tests from this Swedish Audio group in the past.

Here is a partial translation of some of their work that I could still find: http://www.sonicdesign.se/amptest.htm

Their experimental procedures were debatable, and what was represented to me initially as being a DBT turned out to be a SBT.

Please try to save yourself time by not spending it by processing useless information.
 

Arnold Krueger

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Yes. I thought s article in Linear Audio 'Testing, one, two, three...' was interesting as he used the opamps in a more usual role as buffer or gain-of-one driver. IIRC his threshold of detecting the opamps in the circuit was 5 or 6 in series. Double blind test although only one man's result, but a good example of how to design this type of test.


Unlike some other papers mentioned here lately, this one was easy to find, and as complete English text! It is here: https://linearaudio.net/sites/linearaudio.net/files/LA Vol 2 Yaniger(1).pdf. There is a lot there to agree with related to the issues related to subjective testing, and even has an example of testing op amps which is similar to some work that we did back in the days when we were promoting ABX and had hardware to sell.
 

Arnold Krueger

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Speaking of the THD (and IM distortion) - what is actually percieved as a noticeable distortion? Let's assume I have integrated amp which measures 0.08% of THD and IM distortion over the hearing freq spectrum. Would I be able to tell the difference if I swap it with the integrated amp that has say 0,008% of THD and IM distortion?


Differences like these are highly dependent on how you listen, both the total system including sonic environment, and the program material, For example if your program material is composed of pure tones at 19 and 20 KHz then IME 0.08% nonlinear distortion is generally highly audible, and 0.008% is not audible at all.

With randomly selected musical program material, not so much.

A room with relatively high audible background noise might bury the results of 0.08% nonlinear distortion and the twin tones. But a normal listening room with ca. 40 dB SPL household noises is insufficient to mask them.
 

Arnold Krueger

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Hahaha :)

I know how to convert THD % to dB but this shoutometer comparison is really giving things a new perspective! Does it have something to do with the real shouting scenario in the otherwise quiet space (mountain for example) or your figures were just for fun?

Where I get into this is that good loud shout is easily 100 dB SPL at 1 meter. A scream can be 130 dB SPL at 1 meter.

9 kilometers is 9000 times the distance and a fair approximation might be that the SPL falls off with the square of the distance. So, the square of 9000 is about 81 million and a factor of 81 million is equivalent to attenuation of about 164 dB. I'm not expecting to hear that shout at 9 KM.

IME in the backwoods I can hear a gasoline generator running a couple 3 KM away, and that is more like 105 dB SPL and 140 dB attenuation with the same presumptions. Suggests to me that the above presumed attenuation is pessimistic.

But at 100 meters, the presumed attenuation is more like 95 dB, and if its a really, really quiet day, then maybe.

So, can you hear someone shouting at you from the other end of a football field? I'd guess yes.

Some of that might be due to the fact that the human voice is directional, and the estimate of sound falling off with the square of the distance may fall apart because that presumes pure 2-dimensional spreading.
 

Thomas savage

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Please try to save yourself time by not spending it by processing useless information.
Please try and save yourself time by not spending it worrying about how others spend theirs, you can better use that time Learning how to communicate with folk in a more affable manner.

Much needed it would seem.
 

Wombat

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Please try and save yourself time by not spending it worrying about how others spend theirs, you can better use that time Learning how to communicate with folk in a more affable manner.

Much needed it would seem.

General reply,

Affability doesn't always work with folk who will stubbornly defend questionable material that supports their point of view.

Sometimes a more direct presentation of response is needed to cut-through circular comments. o_O
 
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oivavoi

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General reply,

Affability doesn't always work with folk who will stubbornly defend questionable material that supports their point of view.

Sometimes a direct presentation of response is needed to cut-through circular comments. o_O

For clarification: is the implication here that I'm one of those who will "stubbornly defend questionable material"? If not, what is the relevance of your comment in this context?
 

Wombat

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For clarification: is the implication here that I'm one of those who will "stubbornly defend questionable material"? If not, what is the relevance of your comment in this context?

I said my reply was general. That is what I meant.

The relevance of my reply was to post #114, giving an opinion that affability is not the only approach in some circumstances.

Is there a brief affable way of saying 'put up or shut up'? ;)
 
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Krunok

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Differences like these are highly dependent on how you listen, both the total system including sonic environment, and the program material, For example if your program material is composed of pure tones at 19 and 20 KHz then IME 0.08% nonlinear distortion is generally highly audible, and 0.008% is not audible at all.

With randomly selected musical program material, not so much.

A room with relatively high audible background noise might bury the results of 0.08% nonlinear distortion and the twin tones. But a normal listening room with ca. 40 dB SPL household noises is insufficient to mask them.

I'm listening music, not 19 and 20kHz tones. At my age I cannot hear over 13 kHz, I seriously doubt anyone over age of 50 can. I would say my listening room falls into "normal" category.

When I compare my tube preamp/amp combo (which has 0.5% of cumulative THD) with my Rotel setup, I can tell them apart with good recordings, but not in a way that tube setup sounds distorted, it sounds less "bright". I,m pretty sure though I won't be able to tell the difference in a true blind test.
 

Wombat

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A
I'm listening music, not 19 and 20kHz tones. At my age I cannot hear over 13 kHz, I seriously doubt anyone over age of 50 can. I would say my listening room falls into "normal" category.

When I compare my tube preamp/amp combo (which has 0.5% of cumulative THD) with my Rotel setup, I can tell them apart with good recordings, but not in a way that tube setup sounds distorted, it sounds less "bright". I,m pretty sure though I won't be able to tell the difference in a true blind test.[/QUOTE

You well may differentiate in a true blind test. You may be validated. Then again, may not be. If you are happy with your choices don't take the test. If you wish to convince others ............................ .
 
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