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opamps THD+N/IMD/SNR measurements don't mean jack IRL, so let it go humm'kay?

Discussion in 'Sound Science' started by leeperry, Dec 31, 2011.
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  1. 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 [​IMG]
    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 ####.
    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 redface.gif
    So feedback is evil, and opamps measurements don't mean jack. Thanks for passing by.
  2. 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?
  3. 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...
  4. 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.
    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.
    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 [​IMG]
    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?

    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".
  5. nick_charles Contributor

  6. SanjiWatsuki




    Response given.
  7. firev1
    ^^^^ +1

  8. 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. 
  9. leeperry

    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.
    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 [​IMG]
    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.
    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.
    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.

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

    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 ?
  11. 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"
  12. 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?
  13. SanjiWatsuki

    You're sidestepping a lot of my points, and trying to attack others that are put out of context. 
  14. 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
  15. leeperry
    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:
    Always the same story, the Benchmark DAC-1 measures amazingly well gnagnana..
    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.

    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.
    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!

    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.
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