[leeperry]

Hey guys, so many threads end up closed due to Team ThreadCrap whose members always feel like showing biased measurements and explaining to the world that their $90 amp sounds exactly the same as any $3K amp, meaning that anything costing more than $90 is audiophool snake oil yada yada...they also honestly seem to believe that their duty is to save the humanity from being robbed.
 
So I thought it was time to finally put an end to all this, and I've got clues this time

 
A design engineer who's a discrete believer recently told me:

Measured data is valuable, but by no means the most important thing in building high end audio gear. It is very, very easy to build a unit from a handful of chips (opamps) that performs very well on the meter, but sounds awful. Feedback circuits were invented because of their ability to correct for everything – by this it is easy to achieve 0.0005% THD figures. Music is not pure sine waves, not even a sum of two (intermodulation).

 
Couldn't have said it better, yes 5532 is the RMAA pimp daddy yet it does sound like ####.
 
http://www.diyaudio.com/forums/everything-else/88894-discrete-components-better-than-opamps.html

There are certain type of components that have no IC equivalent. Transformers, for example. It is hard to duplicate or exceed transformer performance with op-amps

 

to me a well-designed discrete circuit sounds better, and i've rolled a lot of op amps. they all sound different from each other, so i couldn't imagine how they don't degrade the sound. to me the difference between various op amps even within the same manufacterer is like night and day. people with half-decent ears (like myself) should do a blind test comparing a cascade of op amps to straight wire. that will effectively demonstrate that op amps suck.

 

 
http://www.gearslutz.com/board/4432704-post5.html

there were many scientific researches that proved that all variations of IMD, THD, THD+N tests, and all other specific tests can't be used to say how well the sound is reproduced in terms of subconscious human perceptions. And there still are some stubborn engineers and scientists who won't see any evidences.

 
and I see that the latest Sabre DAC chips carry built-in opamps now, so every manufacturer will throw killer THD+N measurements at 'cha as if they meant anything useful at all.
 
If Audio-GD decided to call all their latest DAC's "No Feedback", there's a good reason to it
 
So feedback is evil, and opamps measurements don't mean jack. Thanks for passing by.

 

[mikeaj]

I'm guessing you must hate most recorded music, which has been through many 5532 and other op amps?
 
Anyway, I agree that often opamp THD+N/IMD/SNR don't matter for audio playback for humans to listen to, if you're trying to distinguish between some different options.  For a decent group of suitable parts for audio purposes in different designs, many of the options are all overkill anyway, so it doesn't matter too much which you use as long as it will work properly.  Past a certain point you should be more worried about stability (and cost).
 
What's up with a lot of the results where people can't even tell when a (sufficiently good) A/D -> D/A loop has been inserted in their playback chain, much less some op amps?

 

[Vkamicht]

So we're dismissing objective measurements in favor of phrases like "sounds awful" and "sounds like ####." To who, you? Me? Keep your panties on, I understand the point you're trying to make, but this thread doesn't prove/disprove anything or provide insight into anything at all. At one point there was a passing suggestion to a blind test, but that's all it was...

 

[leeperry]

Oh yah, I forgot those measurements: http://audio.an-pan-man.com/files/rmaa/earth_vs_moon_vs_sunv2_vs_lt1469.htm
 
If the 3 discrete A-GD opamps sound the same, then I'm the new king of England. I shall claim my throne very soon.
 

I'm guessing you must hate most recorded music, which has been through many 5532 and other op amps?

 
Yep, I definitely don't enjoy listening to music from the 80's. The best sounding music to my ears is from the 70's and yes it did go through valve equipment.
 

For a decent group of suitable parts for audio purposes in different designs, many of the options are all overkill anyway, so it doesn't matter too much which you use as long as it will work properly.

 
Well, all opamps sound different in many ppl's experience. And yes, I can easily identify the nasty SQ of 5532 for instance. When you own so-called "transparent" source equipment, you're basically listening to the opamps that your music material was forced to get through.
 

What's up with a lot of the results where people can't even tell when a (sufficiently good) A/D -> D/A loop has been inserted in their playback chain, much less some op amps?

 
I honestly wouldn't know

 
Last time a member of Team ThreadCrap(now banned) tried to make a point that all DAC's sounded the same(to him at least), I passed his test: http://www.head-fi.org/t/502889/so-who-can-abx-this-recording-from-the-source
 
How could he honestly believe that 5532's and 4562's wouldn't color the sound?
 

So we're dismissing objective measurements in favor of phrases like "sounds awful" and "sounds like ####." To who, you? Me? Keep your panties on, I understand the point you're trying to make, but this thread doesn't prove/disprove anything or provide insight into anything at all. At one point there was a passing suggestion to a blind test, but that's all it was...

Well, all that matters is whether it sounds good to *YOUR* ears...we all know that buying equipment based on cyber-hearsay does not work. My point is that manufacturers throwing killer opamp based measurements as if it were the be-all/end all of audiophilism is the real con. Know your enemy.
 
And what's "objective" about measurements that were compensated by a feedback system again? I don't think you got the memo.
 
Oh well, I guess could dig for hours through google and show why feedback is evil and allows to cheat for killer measurements. Maybe even A-GD has a section on why he calls all his newest DAC's "No Feedback".

 

[nick_charles]

Quote:

Oh yah, I forgot those measurements: http://audio.an-pan-man.com/files/rmaa/earth_vs_moon_vs_sunv2_vs_lt1469.htm
 
There are some rather more extensive measurements on two of the Audio-GD opamps at http://www.sg-acoustics.ch/analogue_audio/ic_opamps/index.html
 
The picture is rather less flattering - so much for design it by ear

 

 

[SanjiWatsuki]

 

Oh yah, I forgot those measurements: http://audio.an-pan-man.com/files/rmaa/earth_vs_moon_vs_sunv2_vs_lt1469.htm
 
If the 3 discrete A-GD opamps sound the same, then I'm the new king of England. I shall claim my throne very soon.
 
Ignoring the issues with RMAA, those RMAA measurements are so close to each other that I'll bet all 3 sound the same. Have you ever heard the difference between -95.4dBr and -93.8dBr? I can't. I'm not sure what you're trying to prove by showing those measurements unless you're starting from your conclusion.
 
Yep, I definitely don't enjoy listening to music from the 80's. The best sounding music to my ears is from the 70's and yes it did go through valve equipment.
 
No, no. Even professional audio equipment goes through 5532s today. Hell, a lot of professional audio equipment still uses a 4558 op amp. I think you overrate the op-amps that are used in professional lines of work. 
 
Well, all opamps sound different in many ppl's experience. And yes, I can easily identify the nasty SQ of 5532 for instance. When you own so-called "transparent" source equipment, you're basically listening to the opamps that your music material was forced to get through.
 
 
I honestly wouldn't know 

 
Last time a member of Team ThreadCrap(now banned) tried to make a point that all DAC's sounded the same(to him at least), I passed his test: http://www.head-fi.org/t/502889/so-who-can-abx-this-recording-from-the-source
Since these are both tied into the same I'll address them both. First off, that test is not a good test of DACs or op amps -- it's simultaneously a test of ADC technology. I don't know ADC technology as well, but I do know that much more care is put into ADC technology rather than DAC technology in the professional field. If you think about it logically, this makes sense -- the actual playback is less important in the studio, rather then the actual recording. There's a lot more care in that area. The DAC portion takes a complete backseat to the rest of the technology. 
 
As for that test specifically, look at all of the factors that are being tested here: 
1. It's an Essence STX, an internal sound card. This makes it partially a test of the electrical grounding of the original poster's computers
2. It's a test of the Essence STX's ADC, which is a far worse component than its DAC.
3. It's a test of ths Essence STX's DAC and amp.
4. It's a test of your DAC and amp.
5. He even got the levels matched wrong.
All of these factors are in the chain and, in all honesty, makes it not a test worthwhile.
 
How could he honestly believe that 5532's and 4562's wouldn't color the sound?

Well, all that matters is whether it sounds good to *YOUR* ears...we all know that buying equipment based on cyber-hearsay does not work. My point is that manufacturers throwing killer opamp based measurements as if it were the be-all/end all of audiophilism is the real con. Know your enemy.
 
And what's "objective" about measurements that were compensated by a feedback system again? I don't think you got the memo.
 
 
Oh well, I guess could dig for hours through google and show why feedback is evil and allows to cheat for killer measurements. Maybe even A-GD has a section on why he calls all his newest DAC's "No Feedback".
 
Who actually uses RMAA to prove these points? You're beating on a strawman here.

 

 


Quote:

Hey guys, so many threads end up closed due to Team ThreadCrap whose members always feel like showing biased measurements and explaining to the world that their $90 amp sounds exactly the same as any $3K amp, meaning that anything costing more than $90 is audiophool snake oil yada yada...they also honestly seem to believe that their duty is to the save the humanity from being robbed.
 
So I thought it was time to finally put an end to all this, and I've got clues this time

 
A design engineer who's a discrete believer recently told me:
 
Couldn't have said it better, yes 5532 is the RMAA pimp daddy yet it does sound like ####.
 
I will admit, as someone who is not a sound engineer, I won't comment on the feedback circuit. What I will say is still that RMAA is not the end-all for metrics and I still don't see many people use it on the Sound Science forum.
 
http://www.diyaudio.com/forums/everything-else/88894-discrete-components-better-than-opamps.html
 
Nice job not showing the other part of that post.
 
 
Quote:

IC's are good at making circuits that are flexible, and consistent. The matching of transistors in an IC can be very nearly perfect which can lead to better performance than discrete parts which can't be matched as well. The manufacturing techniques used in IC yield parts that behave pretty consistently from one device to the next.

 
Your quoted portion talks purely about the powering aspect of op amps versus transformers -- this is more important for speaker amplifiers, like a class A power amplifier. Discrete components would be preferred for making power amps due to the higher amount of power and current required. Speakers, with their lower impedances, require more current and naturally gravitate away from op amps, but often times struggle with ever-increasing current. Even the high end OPA627 caps out at +- 18V. That's nowhere close to the power that some speakers can pull from a powered amp. 
 
That's what this post is saying op amps come up short. This has nothing to do with the actual sound output, this has to do with the power output and where op amps should be used.
 

 
http://www.gearslutz.com/board/4432704-post5.html
 
You're pulling a post out of context again. The poster in question posted a study to back up his findings later in the topic, but that study really didn't say anything to back up what he saying. The study was a test to see if non-linear distortion would make music less tolerable for people to hear.  Of the 21 stimuli, only one them averaged above "imperceptible" by the subjects, and it was only 0.18 points above the imperceptive rating. Regardless, this says nothing about op amps, this is all about putting non-linear distortion into music and whether or not it has a perceptible difference. Overall, it was a paper that was suggesting that this Geelee measurement be used for measuring distortion levels, rather than THD+N% and IMD, because it takes linearity of the distortion into account. All it is saying is that distortion at different places is more annoying than a linear amount of distortion. 
 
and I see that the latest Sabre DAC chips carry built-in opamps now, so every manufacturer will throw killer THD+N measurements at 'cha as if they meant anything useful at all.
 
In many cases this is true -- pretty much every well designed circuit has distortion low enough to not matter. 

 
If Audio-GD decided to call all their latest DAC's "No Feedback", there's a good reason to it
 
So feedback is evil, and opamps measurements don't mean jack. Thanks for passing by.

 
Response given.

 

[firev1]

^^^^ +1
 
Quote:

Oh yah, I forgot those measurements: http://audio.an-pan-man.com/files/rmaa/earth_vs_moon_vs_sunv2_vs_lt1469.htm
 
If the 3 discrete A-GD opamps sound the same, then I'm the new king of England. I shall claim my throne very soon.
 
Rmaa results are like no results, disregarded.
 
 
Yep, I definitely don't enjoy listening to music from the 80's. The best sounding music to my ears is from the 70's and yes it did go through valve equipment.
 
Something I partially agree with, valve amps tend to do better on studio recording(not playback) according a certain AES paper. http://milbert.com/articles/tubes_vs_transistors

 
Well, all opamps sound different in many ppl's experience. And yes, I can easily identify the nasty SQ of 5532 for instance. When you own so-called "transparent" source equipment, you're basically listening to the opamps that your music material was forced to get through.
 
Optimum implementation of 5532s will get you better results.  
 
 
I honestly wouldn't know

 
Last time a member of Team ThreadCrap(now banned) tried to make a point that all DAC's sounded the same(to him at least), I passed his test: http://www.head-fi.org/t/502889/so-who-can-abx-this-recording-from-the-source
 
How could he honestly believe that 5532's and 4562's wouldn't color the sound?
 
Maybe we should try such a test with the Benchmark line of converters, that would be interesting as a prove of concept on the 5532's color.

Well, all that matters is whether it sounds good to *YOUR* ears...we all know that buying equipment based on cyber-hearsay does not work. My point is that manufacturers throwing killer opamp based measurements as if it were the be-all/end all of audiophilism is the real con. Know your enemy.
 
 
 
And what's "objective" about measurements that were compensated by a feedback system again? I don't think you got the memo.
 
No offence to the DIY community or anyone but I would rather trust Audio Precision, DScope and the knowledgeable guys from Sennheiser and other manufacturers who are using their(audio precision) products for their reference.
 
Oh well, I guess could dig for hours through google and show why feedback is evil and allows to cheat for killer measurements. Maybe even A-GD has a section on why he calls all his newest DAC's "No Feedback".
 
I can do the same for digging up papers to show why some measurements are important in audio.  
 
 

 

 

[vrln]

Interesting thread, keep the posts coming During my audio hobby I´ve gone through phases. Originally I was an audio objectivist, but I have to admit I have a soft spot for R2R DAC chips, no feedback gear and so on. Subjectively the Audio-gd REF7 is still the best DAC I´ve heard, and I´ve heard quite a lot. Everything from studio gear to discrete NFB gear. That said, component synergy is the most important thing, electrostats for example sound better on something like the Sabre32. To assess what is ultimately "better" in this hobby, is a tough job. I´d just say that it depends on mood, listening time (quick blast vs long term listening) etc.
 
In the end I always prefer gear that have no listening fatigue. And usually those are NFB designs with R2R chips (the chip isn´t all that important though, the digital filter makes more of an effect than the chip IME) and discrete output stages. Currently my DAC is the Hegel HD20 though, which is a rare thing: a modern IC NFB design. Never heard opamps sound so much like high end vinyl. I should open this DAC someday just to see what components are used. From what I´ve read it´s an AD1955 dual mono with a multi-stage upsampling (latest AKM chips). Quite funny that it runs the same chips as the Benchmark, which shows that implementation is king. It couldn´t sound more different to the Benchmark, almost the polar opposite. What makes it even more funny is that it measures ruler flat to 20kHz and has a great noise floor etc. Still sounds so completely different. Both have their strenghts though. I´ve also heard IC gear that sounds more "tube" than any tube gear I´ve heard - the Violectric V200. 

 

[leeperry]

 

There are some rather more extensive measurements on two of the Audio-GD opamps at http://www.sg-acoustics.ch/analogue_audio/ic_opamps/index.html
 
The picture is rather less flattering - so much for design it by ear

Yep, and the best opamps in this huge PDF are of course the ones he builds and sells ^^
 
And he did blind opamp rolling to the extreme, how can you dare rolling AD797 and LT1028 blindly? I wouldn't know.
 
My point when showing those A-GD discrete opamps measurements was that their feedback system would get them all to measure pretty much identically....and if Sun-V2 and Earth sounded the same to someone, I would advise him to switch hobbies, buy an ipod, its matching dock and move on. Measuring opamps is utterly meaningless, it won't tell you anything about how they'll sound IRL.
 

Ignoring the issues with RMAA, those RMAA measurements are so close to each other that I'll bet all 3 sound the same. Have you ever heard the difference between -95.4dBr and -93.8dBr? I can't. I'm not sure what you're trying to prove by showing those measurements unless you're starting from your conclusion.

 
I don't think you have read what I wrote in the OP, and I also presume that you have never heard those 3 discrete opamps(I have). There's an implied rule on head-fi that ppl shouldn't talk about gear they haven't heard for themselves. Earth, Moon and SunV2 sound all extremely different from one another....they measure pretty much identically, oh yes they do...big deal when their feedback system cons your meter

 

Even professional audio equipment goes through 5532s today. Hell, a lot of professional audio equipment still uses a 4558 op amp. I think you overrate the op-amps that are used in professional lines of work.

 
Oops, I should have made clear that I hardly ever listen to >1979 music, coz the SQ is hardly ever up to my personal standards. I'm well aware that pro audio gear runs the crappiest opamps ever...like those snake oil RME/Lynx über-pricey internal soundcards that newbie audiophiles like to call the top of the crop. All they have for them is good clocking, but they use a stellar ripple and very noisy shared ATX PSU and crappy 5532/2068/4580 opamps. They justify their prices by running excellent drivers, but clearly you're not paying for audiophile grade hardware.
 

 
Since these are both tied into the same I'll address them both. First off, that test is not a good test of DACs or op amps -- it's simultaneously a test of ADC technology. I don't know ADC technology as well, but I do know that much more care is put into ADC technology rather than DAC technology in the professional field. If you think about it logically, this makes sense -- the actual playback is less important in the studio, rather then the actual recording. There's a lot more care in that area. The DAC portion takes a complete backseat to the rest of the technology. 
 
As for that test specifically, look at all of the factors that are being tested here: 
1. It's an Essence STX, an internal sound card. This makes it partially a test of the electrical grounding of the original poster's computers
2. It's a test of the Essence STX's ADC, which is a far worse component than its DAC.
3. It's a test of ths Essence STX's DAC and amp.
4. It's a test of your DAC and amp.
5. He even got the levels matched wrong.
All of these factors are in the chain and, in all honesty, makes it not a test worthwhile.

 
The STX is using a bunch of 5532's on its line-in, it also measures amazingly well in both AP and RMAA. It's the perfect example of this opamp feedback bs that falsifies measurements and allows companies to sell shrill sounding gear on the promises of inaudible distortion.
 
It's only a line-out>line-in loopback on the STX, which carries some of the killerest measurements you can find...it's all inaudible, remember? So how come the drums sound flat and boring on the loopback? 5532's at work my good friend.
 

This has nothing to do with the actual sound output

 
Indeed, because all opamps measure the same...it would very much appear that the only way to know how a piece of equipment based on opamps sounds is to listen to it with your own ears. Their feedback system falsifies measurements for the best and turns any shrill sounding shiny box into a measurements fairy tale.

Maybe we should try such a test with the Benchmark line of converters, that would be interesting as a prove of concept on the 5532's color.

 
It's rather sad to read the Benchmark ppl stating clearly here on head-fi that 5532 is the best solution ever for headphones amplification and that 4562 is the best chip for DAC filtering...sad story, really.
 
Their DAC-1 and the DacMagic both use equally poor sounding IC chips, and in this review against a legendary discrete DAC they both got shot down(as expected): http://ravenda.wordpress.com/2009/08/14/audiogddac19/
 

1. Benchmark DAC1 ($995 ~ harsh, flat out boring)
2. Cambridge DACMagic ($429 ~ does not sound any better than a $99 NuForce uDAC, a disappointment)

 

Optimum implementation of 5532s will get you better results.

 
You mean "oscilloscope results" I guess. Yes, 5532 measures amazingly well...too bad it sounds equally as bad.

 

[nick_charles]

Quote:

Snip...

 
You keep falling back on sighted subjective reviews - these are not held in such high esteem in these parts due to their inherent unreliability - that and frequent calls to authority again of limited empirical value - if the audible differences between similarly measuring components are really **so obvious** why not share the results of some properly proctored DBTs with us ?
 
 

 

[jcx]

does this thread have a history? - was it cut from somewhere else and dumped here?
 
odd to step into the Sound Science "ghetto" and start spouting slogans, "waving the bloody shirt"
 
 

 

[mikeaj]

Even supposing you can hear things (and furthermore, after they've been through very imperfect transducers) better than precision instrumentation can't pick up...
 
I don't see how feedback "falsifies measurements" if that's how the circuit's been designed?  What's being implied is that the op amps don't measure that well without feedback, and therefore with feedback they sound bad?

 

[SanjiWatsuki]

 
Quote:

I don't think you have read what I wrote in the OP, and I also presume that you have never heard those 3 discrete opamps(I have). There's an implied rule on head-fi that ppl shouldn't talk about gear they haven't heard for themselves. Earth, Moon and SunV2 sound all extremely different from one another....they measure pretty much identically, oh yes they do...big deal when their feedback system cons your meter

 
This is the Sound Science forum, my friend. I'm afraid this doesn't help me any. You're right, though, I don't go out DIY op amp rolling. You're using a logical fallacy, though, you're starting from your conclusion to make your point. By assuming that they sound different and asserting only your word, you suggest the measurements are flawed, rather than showing something to back up why they sound different. All I did was interpret the measurements in front of me, which are RMAA and can't be trusted to start. As I said in my last post, and you ignored, RMAA has issues and I pretty much never see anyone use them in actual arguments on the Sound Science forum. Every time you bring RMAA up or the flaws with a feedback system, you're attacking a strawman. 
 
Oops, I should have made clear that I hardly ever listen to >1979 music, coz the SQ is hardly ever up to my personal standards. I'm well aware that pro audio gear runs the crappiest opamps ever...like those snake oil RME/Lynx über-pricey internal soundcards that newbie audiophiles like to call the top of the crop. All they have for them is good clocking, but they use a stellar ripple and very noisy shared ATX PSU and crappy 5532/2068/4580 opamps. They justify their prices by running excellent drivers, but clearly you're not paying for audiophile grade hardware.
 
Where did sound cards into the mix? You just side-stepped the issue of the music already running through the op-amps by moving onto a tangent about electrical grounding with internal sound cards. I don't see the relevance of the 1979 comment -- professional audio equipment still uses those "crappiest op amps." I don't understand how this deflects any of the points.
 
The STX is using a bunch of 5532's on its line-in, it also measures amazingly well in both AP and RMAA. It's the perfect example of this opamp feedback bs that falsifies measurements and allows companies to sell shrill sounding gear on the promises of inaudible distortion.
 
It's only a line-out>line-in loopback on the STX, which carries some of the killerest measurements you can find...it's all inaudible, remember? So how come the drums sound flat and boring on the loopback? 5532's at work my good friend.
 
You're ignoring the rest of the points I made there. I'm saying you can't localize the issue to the op amp. You yourself brought up the issue of electrical grounding, which I agreed with. 
 
 
Indeed, because all opamps measure the same...it would very much appear that the only way to know how a piece of equipment based on opamps sounds is to listen to it with your own ears. Their feedback system falsifies measurements for the best and turns any shrill sounding shiny box into a measurements fairy tale.
 
What? You pulled that statement out of context! I was saying your proof for op amps sounding differently was a post on power, not on the sound quality! You twisted that into some kind of argument about feedback systems and measurements. All I was saying was that the post argued that transformers are better for high power usage and are used on powered amps, a point which I agree on, and was saying how op amps were not suitable for that work. 
 

 
You're sidestepping a lot of my points, and trying to attack others that are put out of context. 

 

[jcx]

I found http://www.head-fi.org/t/432749/the-opamp-thread/3615#post_8016820 but really still don't see the context/provocation for launching this thread
 
its hard to see how messed up/fragile someone's belief system must be to start rug chewing playing the "thread crapping" card, etc over  ~1 % of the posts reminding people of objective requirements for successful op amp operation, achieving low noise, output swing, avoiding oscillation...
 
even smaller fraction of the "objectionable, thread crapping posts" are pointing out there is strong reason to be skeptical of the thread's acceptance of any/all subjective reports when most participants don't know/use the known results for increasing reliability of subjective comparisons
 
the DIY subforum has to accept more "objective", engineering input if people are expected to make working circuits, or even appropriately select op amps to roll, understanding the circuit they are used in
 
it is a disservice to all of head-fi for people to be "protected" from dissenting opinion, especially when they censor actual accepted Science, engineering inputs to the discussion
 
for a closed clique that just want to talk to themselves I can see their not wanting the "distraction" - but the op amp rolling thread in the DIY forum in particular keeps attracting newbies - who deserve to be exposed to diverse information
 
 

 

[leeperry]

 

does this thread have a history?

 
Ah well, I'm not sure I will find the time and energy to conduct another pointless thread here on head-fi but I can show you quite a lot of threads that got closed due to opamps measurements threadcrapping:
 
http://www.head-fi.org/t/577535/o2-build-complete-let-the-objective-subjective-listening-tests-commence/720#
 
Always the same story, the Benchmark DAC-1 measures amazingly well gnagnana..
 
http://www.head-fi.org/t/576629/does-which-dac-you-have-really-matter/120
 
The OP asks a simple question, and his thread gets trolled for almost 10 pages by (biased) measurements objectivists and eventually gets closed.
 
And there's more, believe me.
 
Why did I say "pointless debate"? coz it always boils down to ppl who haven't done their homework, talk about gear they haven't heard and act as self-proclaimed experts.
 

if the audible differences between similarly measuring components are really **so obvious** why not share the results of some properly proctored DBTs with us ?

The feedback mechanism that is built into opamps renders their measurements meaningless, so tell me...if we can't trust measurements, what else can we trust apart from our good ole ears? Have you ever heard a high end discrete DAC? Did it sound the same as a PCM1793/NE5532 combo to your ears?
 
You're a notorious myth debunker(your cable shoot-out was quite something), how about going to a head-fi meeting and come back telling us that all DAC's sound the same? For what we know, they all measure "beyond audibility"...or so I read anyway.
 

I don't see how feedback "falsifies measurements" if that's how the circuit's been designed?  What's being implied is that the op amps don't measure that well without feedback, and therefore with feedback they sound bad?

 
Feedback is cheating, plain and simple. Their measurements neither mean or prove anything.
 
But now that you mention it, many ppl claim that it sounds bad too: http://gilmore2.chem.northwestern.edu/projects/
 
"It has zero global feedback for open, natural sound without any harshness"
 
So feedback fasifies measurements and sounds shrill, goodness gracious!
 

You're right, though, I don't go out DIY op amp rolling.

So I'm telling you that opamps measurements don't mean jack, that these 3 opamps sound drastically different. You tell me that the measurements prove that they all sound the same, and yet you haven't heard any of them...how is that useful to anything? Let me repeat it for you once more, because maybe I didn't make myself clear from the get go: "Feedback circuits were invented because of their ability to correct for everything – by this it is easy to achieve 0.0005% THD figures". They will always all measure the same, OTOH it's quite astounding to read ppl saying "hey fellas, I've measured a lot of opamps and they all measured the same, and they all sounded the same to me too!!! placebo!! snake oil!! attack!!!". If OPA1641 and OPA602 sound the same to you, I would also advise to switch hobbies....you're wasting your time.