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opamps THD+N/IMD/SNR measurements don't mean jack IRL, so let it go humm'kay? - Page 3  

post #31 of 134
12/31/11 at 7:22pm
Thread Starter 

 

Originally Posted by SanjiWatsuki View Post

you're not even trying to make an argument anymore.

 

Point taken, I've quoted a very skilled EE who knows what he's talking about...but you asked so nicely, that it shall come after all: http://physics.usask.ca/~angie/ep316/lab7/theory.htm

op amps are designed for use in a feedback loop

http://sound.westhost.com/dwopa.htm

An opamp will attempt to make both inputs exactly the same voltage (via the feedback path)

http://www.circuitstoday.com/integrated-circuits-merits-and-demerits

Need of connecting inductors and transformers exterior to the semi-conductor chip as it is not possible to fabricate inductors and transformers on the semi-conductor chip surface.
Voltage dependence of resistors and capacitors

 

Real world facts are that an opamp will never sound as good as a discrete output stage, hopefully some EE will be bored enough to explain us why. I've never claimed to be an EE, I'm just pinpointing that opamps measurements are biased due to their feedback loop and that many manufacturers want you to believe that killer measurements are what audiophile equipment is all about...when it couldn't be farther from the truth really.

 

I know Kingwa has a forum, but I think it's chinese only...He must have explained why he called all his newest units "no feedback". I could spend hours torturing google for why feedback is bad, but tbh I've got nothing to prove nor to sell here.

 

Originally Posted by Br777 View Post

this is what leeperry does, over and over and over.. thread after thread. 


And this is the kind of posts Br777 makes over and over again, did he learn from the best(30x30px-ZC-89945f31_9190-Head-Fi+Avatar.png) ? bigsmile_face.gif

 

Originally Posted by mikeaj View Post

This statement has got to be a goldmine for entertaining interpretation, particularly if you don't restrict "feedback" to the electrical or systems theory sense, but I'm not quite in the mood for digging today


I'm sad to read that you're "not quite in the mood" today, but OTOH I'm glad to read that you actually seem to require very little to be entertained! more power to you my good man.


Edited by leeperry - 12/31/11 at 7:36pm
post #32 of 134
12/31/11 at 7:30pm
Thread Starter 
Originally Posted by nick_charles View Post

one last attempt


a very nice attempt at that, the kind of meaningless discussions we've been having since forever biggrin.gif

 

Originally Posted by nick_charles View Post

1. Then if it is that obvious it will easily survive a decent DBT

2. Show me anywhere in this thread where I have used that word, I am very careful about using that word

3. Not really, it is a big subjectivist discussion unsupported by empirical unbiased listening tests

 

1. It sure will. Any opamp roller can DBT all those chips anytime you want...just like that quote from diyaudio said:

 

"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."

 

He has said it all reallypopcorn.gif

 

2. It was implied and you know it...you hide behind measurements noone was bored enough to conduct, and the only measurements we have are biased due to the feedback loops of those IC's. And then you call any audible difference "bias" or implied "placebo". Same ole, same ole really.

 

3. I've heard most of the chips in this shout-out, and so did many other rollers, and we all pretty much agree with his conclusions. You don't seem to have ever heard any of these chips apart from a prolly fake OPA627 in your Zero DAC(and OPA627 is pretty meh, even genuine)...how can you dismiss these real world experiments so easily? majkel is an EE btw, and I've got an audio engineer diploma FWIW.


Edited by leeperry - 12/31/11 at 7:37pm
post #33 of 134
12/31/11 at 7:50pm

.


Edited by nick_charles - 12/31/11 at 7:53pm
post #34 of 134
1/1/12 at 12:12am
Quote:
Originally Posted by leeperry View Post

 


So much nonsense on the same blog deserves an award(balanced headphones amping is snake oil, all opamps sound the same, all volume attenuators sound the same, and it goes on and on), this guy is good! He might even be (one of) the best I've read, so kudos to him! I hope he gets good money from his hard work coz he truly deserves it.
 


 


Wow, what a mean spirited post, lots of insinuation, no facts. I've read his blog and learnt a lot, "yet it does sound like ####." is about all I could have have learnt from your contribution.
 

 

post #35 of 134
1/1/12 at 2:03am
Quote:
Originally Posted by anetode View Post

I'm not sure of the politics of posting this. Nonetheless, Nwavguy's "Op Amps: Myths & Facts" and "Op Amp Measurements" (google them) make for a good read and dispel the majority of leeperry's anecdotal pseudoscience.

 

@anetode:  excellent referrals.  these posts contain op-amp info well worth reading for those interested in the topic at hand.

 

@all:  in the current internet morass outside of head-fi of people who know nothing about underlying technology, but post extensively pontificating about and "reviewing" audio products (to catalyze advertising revenue); or who are "IT Professionals" or "high-end equipment manufacturers" collaborating in self-promotion on "computer audio" websites (to drive product placement and consulting revenues); the referenced blog is IMHO educational, rational, non-commercial, and based in a presentation of solid technology knowledge.  Highly recommended.

 

And, as noted in the referenced posts, look into icons such as Putzeys and Self who really are knowledgeable wrt amplifier design (or Cordell's great book on amplifier design - remember, op-amps are amplifier architectures, whether implemented discretely or in integrated circuit form) for well-informed and substantiated discussion addressing audiophile myths and controversy concerning use of negative feedback in amplifier design.

 

@leeperry 1:  anecdotal, my perspective, along with that I'm comfortable with Sam's presentation:

 

- Sam Groner's op-amp survey and analysis is well-regarded in the engineering world, study and results acknowledged by some slightly-experienced folk such as Walt Jung.

 

- offered as context, I was fortunate to have Bob Cordell as a supervisor and mentor in my first job, at Bell Labs in the early-80s, and have had ongoing interaction with him over the years; I did doctoral studies in dsp, CS and IC design at ETH Zürich (ETH is the german acronym for Swiss Federal Institute of Technology) while working at Studer-Revox on dsp product architectures in the mid-80s -- which allowed me to see the quality of Daniel Weiss' work there first-hand; and I have the pleasure of knowing Daniel quite well (including his exacting high standards).

 

And Daniel hired Sam out of ETHZ five+ years ago to work at weiss.  Says something to me.

 

@leeperry 2:  so, I'm really trying to understand your positioning in this thread.  I can't seem to readily find anything about your background, hence an earnest question, asked to hopefully gain context for your writings:  do you have background or experience in electrical engineering or electronics design?

 

chuck

 

edited:  grammar, formatting


Edited by emmodad - 1/1/12 at 2:15am
post #36 of 134
1/1/12 at 3:54am
Thread Starter 

Well, the EE I quoted in the OP has many commercial discrete designs on the market, he "knows"...and it would appear that EE's that master Non Feedback designs aren't too willing to kill the golden goose and share their knowledge.

 

I've done some extensive googling, and it always boils down to the same story: http://www.diyaudio.com/forums/solid-state/5290-op-amp-chips-signal-path-evil-not-evil.html

The purist reason why op-amps are bad is to do with negative feedback - which is also deemed bad when it operates from the output of a high-gain system back to its input.

 

NFB believers like to use an opamp for DC servo, just like in some of the older A-GD units: http://www.diyaudio.com/forums/solid-state/28448-there-anybody-built-non-feedback-amplifier.html because

that way the "sound" quality of the op amp come out from the equation...

 

Indeed, DC servo seems like a perfect use for an opamp evil_smiley.gif

 

Going NFB is old school, from the good ole valve days. Surely you can go cheap and use IC opamps but they all color the sound drastically...and I think this thread is a good answer to the discrete/IC dillema: http://www.diyaudio.com/forums/solid-state/5290-op-amp-chips-signal-path-evil-not-evil.html

the best discrete design will better the best opamp circuit. while a cheap opamp circuit will best a poorly done discrete circuit.
Miller capacitance is why op-amps are not used in high end amps. Many transistors = lots of Miller. Miller capacitance affects slew rate. If it were all as easy as an OP-Amp, cows would fly.

Use discrete components and as few as possible in the signal path.
Same as everything else in audio, opamps are coloured. If you happen to like their sonic signature - great. As Cunningham's post above says "cows would fly". I use them as sparingly as possible, admittedly it's neither easy nor cheap to completely avoid them.

 

So it costs more and requires more knowledge to avoid them, and you have that nasty "Miller capacitance" issue that needs to be compensated for..opamps sound utterly colored and need to be compensated for everything going terribly wrong: hence, the killer measurements that really don't mean jack in the end as far as subjective critical listening is concerned devil_face.gif

 

Which sends back to my original quote 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". Yes, LM4562 and LME49990 carry killer datasheet specs, but oh gawd do they sounds bad biggrin.gif


Edited by leeperry - 1/1/12 at 4:17am
post #37 of 134
1/1/12 at 5:17am

Sweet Mother of God. I'm not sure where to start. You have managed to foster a deep and unshakable belief in virtually every audiophile myth known to man. Let's run down the list, shall we? I really cannot be bothered to cite sources: these things are so widely refuted by absolutely everyone who isn't involved either emotionally or financially with high-end audio that Google will serve you quite well. Not that I'm under the delusion that you would re-evaluate your beliefs based on anything I might say, but here goes.

 

Myth One: Music is not sine waves/test tones, therefore measurements are all wet.

 

Nope. I don't care what some high-end audio nutjob came out with, this is a myth, born from a strange urge to personify amplifiers, imagining that they think about what they amplify and presumably get confused and muddle the bass line should cheap components be used. See Doug Self's Audiophile Myths.

 

Myth Two: All opamps sound completely different, even when probably implemented.

 

Such utter BS will never survive a blind test, nor a casual application of logic. Why exactly should they sound different again?

 

Myth Three: Measurements cannot possibly cover magical subsconscious hearing magic.

 

See Myth Two. It is not rational to believe in unfalsifiable claims with no supporting evidence.

 

Myth Four: Feedback is evil.

 

A popular myth, touted mainly by audiophiles with a vanishingly slim understanding of electronics and an extreme vulnerability to manufacturer PR. AudioGd sells "no feedback" designs so people like you will buy them. Care to suggest by what measurable mechanism feedback is evil when properly used? Oh, I forgot. Unmeasurable magic fairy dust and the like...I'm not even sure you realise there are different kinds of feedback.

 

You've also mentioned slew rate, which is not really required in very large amounts for audio reproduction, but I'm sure you can hear the difference...

 

 

 

Seriously, why did you post this? The fact you had to look for posts on random forums to back you up should tell you something about the accuracy of what you're coming out with. 

post #38 of 134
1/1/12 at 5:30am

popcorn.gif

post #39 of 134
1/1/12 at 5:47am
Thread Starter 

 

Originally Posted by Willakan View Post

Seriously, why did you post this?


Definitely not to waste my time arguing with you, you're basing your assumptions about audiophile gear on nothing substantial basically. You've also already confessed lacking any kind of real world experience whatsoever about audiophile equipment...you just wave a bunch of meaningless figures you read somewhere else that have no real world impact whatsoever on how it'll sound to the human brain. AHMAHGAD 0.00000000001% THD+N, it sounds so amazing...NOT biggrin.gif

 

There's local feedback, negative feedback, global feedback and so on..TYVM for your attention it's much appreciated o2smile.gif

post #40 of 134
1/1/12 at 5:50am

How can you be so staggeringly deluded to genuinely believe that your casual listening impressions are of any import at all? I couldn't give a toss what you have heard/will hear/what your equally deeply deluded forum psuedoscience buddies heard. I am honestly mystified as to how you maintain your unwavering belief in your magic, bias-proof ears.

 

Your beliefs are simply a mishmash of crap to justify the greatest myth of all: that human hearing is infallible. This is bad enough, but you deliver your ignorant, ill-mannered, badly worded and totally incorrect crap with an air of condescension! What possible reason could you have to believe that anything you have said on this thread makes a whit of sense? It is incredibly hard to respond to your posts in a civil way due to their content and the style of their composition. I would entertain the prospect that you are trolling, but you appear to have thrown considerable sums of money at your beliefs.


Edited by Willakan - 1/1/12 at 5:58am
post #41 of 134
1/1/12 at 6:03am
Thread Starter 

 

Originally Posted by Willakan View Post

 

It is incredibly hard to respond to your posts in a civil way


Yeah, it seems that you could really use a breezer of some sort. Had a rough night, huh? bigsmile_face.gif

 

You own a DacMagic full of nasty sounding 5532's and OP275's, I feel you...but cheer up, it measures amazingly welljecklinsmile.gif

 

http://www.diyaudio.com/forums/solid-state/5290-op-amp-chips-signal-path-evil-not-evil.html#post1569799

As for the OP275, it is particularly coloured IMO. A darkish, pleasant, old tube school type of sound. Quite nice, but not very dynamic or detailed

rastaman40.gif, OP275 sounds unbearable.


Edited by leeperry - 1/1/12 at 6:06am
post #42 of 134
1/1/12 at 6:13am

I bow to your trolling ability, but am now too annoyed to care.

Why are you quoting people off random forums? What purpose does that serve? If you're going to go for a fallacious appeal to authority, choosing people at random is bad idea.

Here is a quote from the Flat Earth Society forums. Consider the undeniable fact that the ISS missions are faked with CGI as provenrolleyes.gif

 

"This is the original space fake program. They hired all the visual effects fakers from Populous 4. Or maybe they created the Populous game, to improve their forging skills."

 

 


Edited by Willakan - 1/1/12 at 6:18am
post #43 of 134
1/1/12 at 6:36am

Epically entertaining popcorn.gif

post #44 of 134
1/1/12 at 8:29am
Quote:
Originally Posted by leeperry View Post

 

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!


I'm going to stick my nose in here, and probably where it doesn't belong, but...

 

Why not ask Dr. Kevin Gilmore, Electrical Engineer at Northwestern University 1-847-491-2962 

http://www.head-fi.org/t/197035/who-is-kevin-gilmore the author of the above quoted prose?

 

...instead of going after Lee Perry.  Lee has every right to argue IC as someone posting how ubiquitously wonderful is the OPA627 in XYZ amp.

 

For the record: I own a version of Dr. Gilmore's Dynalo and it is probably one of the "cleanest", "freshest", "purest" amps I own with lots of bottom end "SLAM", the "sweetest", "juiciest" mids and surgically "precise" highs  bigsmile_face.gif


Edited by Paul Clark - 1/1/12 at 8:38am
post #45 of 134
1/1/12 at 8:50am

There are designers with irrational beliefs. I think you'll find that the majority of electrical engineers would contest Mr. Gilmore's statement as an absurdity, unless it has been taken out of context. Degree'd designers can still hold irrational beliefs and can manage, sometimes, to design good gear in spite of them.

 

The following link (recommended by NwAvGuy on his blog - thus regrettably allowing the chronically irrational to dismiss it out of hand) is a nice discussion of lots of irrefutable maths that conveniently kills every major NFB myth from a Mr. Bruno Putzeys.

 

http://www.linearaudio.net/userfiles/file/letters/Volume_1_BP.pdf

 

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