# Subjective vs measurements in the perception of sound quality



## ppl

The difference between subjective sound qualities of an Audio system vs. the measured performance is the subject of much debate among both Music Lovers and Audio professionals alike. While the typical Engineer type will dismiss any claim of superior sonic performance of one Audio component over another of similar measured performance (The All Amplifiers sound alike camp) and the real or perceived quality of any given Audio component over another by Audiophiles have gone on for decades and as a result have created a nitch market for the Audiophile Press to respond to the concerns of Music lovers that claim to hear substantial differences between seemingly similar components. Magazines like the Absolute sound and stereophile have taken these concerns to heart and as such have flourished longer than the at one time more mainstream of audio rags like Stereo review and High Fidelity. The latter have been perceived as nothing more than long advertisements for the Audio manufactures that advertised with them. The claim that stereo Review never gave a bad review is just one reason Audiophiles have abandoned these and flocked in droves to the once underground press.

 Like any revolution the Subjective perception of sound quality of High fidelity components that seam to defy subjective specifications have caught the attention of the professional Audio community and as a result a lot of research is now directed towards the reason differing components that measure more or less identical of so close as to be unheard by the ears of mere mortals. I have also noticed that even untrained listeners can differentiate between components that perform so well as to make the sanity of anyone that would say any audible difference between the two come into question. 

 Take the continued discussions hear regarding Op Amps, in theory there should be no difference in sound quality between the Burr Brown OPA-627 and the quite similar Analog device AD-8610. This really gets hard for some engineering types to understand since once ether of these two devices is placed in an Amplifier circuit they will measure virtually identical within the audio range. Yet they are perceived almost universally by most members of this forum as possessing slightly different sound. 

 Consider the fact that Op amps are talked about as having differing qualities in the bass reproduction even when both are operated in a Direct coupled configuration. How can this be the case most Engineering types would say as they leave the conversation laughing in utter disbelief, citing the ruller flat frequency and power response all the way down to Direct current? Now consider that most headphones and loudspeakers can not even remotely approach a flat frequency response down to DC. 

 The software industry has tried to take advantage of this and is working on instrumentation that hopefully will quantify the measured results to listener preferences
http://www.alma.org/Http_Pages/ANv5_2.pdf
http://www.mts.com/nvd/Software/pdf/...54_EOL_NVH.pdf
http://www.sae.org/calendar/nvc/ws-wed-sounda.pdf
http://www.picotech.com/applications...tml#amplifiers
http://www.lecroy.com/tm/library/LAB...20/default.asp

 The Audio engineering Society has devoted quite a lot of articles dealing with the performance and sound quality in Audio Amplifiers.
http://www.aes-singapore.org/feb_6_1998.htm
http://www.aes.org/standards/b_pub/aes20-1996.pdf

 The David Burning Company has quite a unique design philosophy regarding Amplifier design.
http://www.meta-gizmo.com/Tri/otlology/BERNINGS.htm

 Its Audio quality research project has some interesting articles on Audio quality however more towards Digital telecom use than Audiophile however still interesting to read
http://www.its.bldrdoc.gov/home/prog...udio/audio.htm
http://www.its.bldrdoc.gov/home/programs/audio/subj.htm

 Stereophile has a quite lengthy article on subjective sound impressions as one would expect from the rag that started all this talk of subjective sound quality.
http://www.stereophile.com/showarchives.cgi?190:

 Simple op amp based headphone Amplifiers p Spice testing is a grate tutorial on what we hear love most. This is a tutorial on using p spice to simulate the parameters of op amp based headphone Amplifiers.
http://www.beigebag.com/case_amp1.htm P Spice intro
http://www.beigebag.com/case_amp2.htm Distortion
http://www.beigebag.com/case_amp3.htm Measuring Input & output Impedance
http://www.beigebag.com/case_amp4.htm maximum power output
http://www.beigebag.com/case_amp5.htm Power Supply Rejection Ratio
http://www.beigebag.com/case_amp6.htm open-loop gain

 A great book for those that of us that are into High end Audio DIY projects available at amazon.com titled The Audiophile's Project Sourcebook review at
http://book.realbuy.ws/0071379290.html
 also remember if you use the amazon.com link on Head-fi front page you will be supporting Head-fi
http://www.amazon.com/exec/obidos/tg...lance&n=507846

 Those that love Tubes will surly like this site Do I need to make a disclaimer hear? I am not a Tube fan and I do not believe tubes are a superior Amplifying Device however some people do and so for those that just love thermionic valves devices.
http://www.allaboutcircuits.com/vol_3/chpt_13/12.html

 back to Solid state Circuits let us not forget the thermal distortion guy at his new web site
http://www.lavardin.com/aesE.html#AES
http://www.lavardin.com/index.html
http://peufeu.free.fr/audio/memory/

 A App note from Maxium regarding Bridged Amplifiers or BTL (Bridge to load) Noise and distortions and gasp class D Amps however good treatment of output stages
http://www.maxim-ic.com/appnotes.cfm...ber/1122/ln/en
http://pdfserv.maxim-ic.com/en/an/AN1760.pdf

 Soundstage magazine describing how thay test Amplifiers
http://www.soundstagemagazine.com/me...amplifiers.htm

 for the novice the How things work is a great site to understand almost anything hear is a link directly related to amplifiers.
http://howthingswork.virginia.edu/audio_amplifiers.html

 Well I hope you are not now more confused that you were prior to reading this post however you should be more enlightened with respect to the differing conflicts that arise when trying to design an Audio component that not only sounds good but also measures well so as to satisfy both the technocrat as well as the Artist among you.


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## john_jcb

This is a great thread.

 I am wondering if it would have greater visability in one of the other forums though??

 Or maybe a sticky here.

 Your thoughts?


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## Gariver

G. Randy Slone's books are 1st class and highly recommended for the DIY crowd. I've got 2 of his amp books.

 Thanks for the highly informative post, ppl!


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## ppl

John I was hoping that this and other posts i posted about be a sticky. and maybe this should be in the Amps section or somthing I don't Know.


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## JohnFerrier

More good posts.


 JF


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## mtlin12

ppl said,
  Quote:


 I am not a Tube fan and I do not believe tubes are a superior Amplifying Device however some people do and so for those that just love thermionic valves devices. 
 

I am not a Tube fan, either. But I still buy a SRPP+Cathode Follower design with 4-tube regulator for AB test.

 I know some Tube fans don't like any solid state in the circuit, they don't want JFET-input like Audio Research LS-25 Mk-II, they say the hybrids sound "too clear ","too modern", they criticise the solid state regulator and prefer using CLC or tube regulator, maybe there are some truth but the measurement can't tell.

 I have read Allen Wright's article of his SP-15, I do agree his viewpoint about shunt regulators are much better than the series regulators.
http://members.ozemail.com.au/~lisar...15_Article.pdf 

 Though I don't know how to test or measure the difference between them.


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## Tom M

Here is a question that might be setup as a poll. How many head-fiers are objectivists and how many are subjectivists? I don't know how to go about stetting up this poll, but maybe one of the moderators might help me on this one.


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## rsaavedra

Very interesting thread. About the social conflict between those who listen and those who measure, and the differences between what measurements suggest, and what people hear, John Atkinson wrote an extremely sharp article a long time ago in Stereophile "A matter of dimensions". That is as current now as it was the day it was published:

http://www.stereophile.com/asweseeit/572/

 Another great read in this same subject is "The Role of Critical Listening in Evaluating Audio Equipment Quality" by Robert Hartley. It also appeared as "The Listeners' Manifesto" in Stereophile:

http://www.stereophile.com/features/20/

 Also appeared featured in "The Absolute Sound", issue 128:
http://www.theabsolutesound.com/back_issues_128.html


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## ppl

“Nature does not solve equations." LOL that is the most absurd statement I have heard taken from this sterteophile link http://www.stereophile.com/asweseeit/572/ 
 With emphasis added. And one can seriously wonder about if the person making such a statement were a surgeon if you would want this person to operate on you. Thanks rsaavedr for adding to this thread I got my much needed light today by the above statement along with others by quoted in stereophile by Richard Heyser. Stereophile and others really do music lovers a great service by exposing over zealous technocrats for the agenda oriented and or completely clueless folks that may be shaping out music reproduction’s future.


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## rsaavedra

Quote:


 _Originally posted by ppl _
*“Nature does not solve equations." LOL that is the most absurd statement I have heard taken from this sterteophile link * 
 

Incidentally I have specifically wondered what the exact context was where Heyser wrote that statement. Would be interesting to find out.


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## rsaavedra

Searching in Google I discovered the sentence "Nature doesn't solve equations" is part of the title of a paper in chemistry, see paper 6 in: http://www.inform.umd.edu/EdRes/Topi...ce/ChemConf97/

 Not that this whole thing is particularly important, but I think it's kind of interesting. This is *not* from the original paper by Heyser, but the idea might be related to what Heyser meant, I think:

_"Today we do admit, when challenged, that the natural phenomena happen without regard to the mathematics that we use to describe them. In other words we accept the fact that *nature does not solve equations*. But we are less comfortable when challenged to explain how the phenomena actually happen." _
 (From: http://fie.engrng.pitt.edu/fie96/papers/253.pdf)

 Next time I'm in a library will try to find the original paper written by Heyser in the Acoustics Eng. Society proceedings.

 Cheers,
 Raul


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## jefemeister

good thread. You've definitely put some research into it. I don't think anyone with ears would say that measurements tell the whole story. It is good that this idea has sparked people into coming up with better measurements though. 

 For a good laugh take a look through Crutchfield. All those head units and amps post up some very impressive numbers. But (A) there is no accepted standard way of measuring things like THD, SNR, etc and (B) they don't guarantee good performance. You can have great specs and plots and sound worthless and on the flip you can have some appaling specs and sound amazing (although this is a bit rarer.)


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## Prune

Regarding ppl's statement concerning how most would differentiate between the sound of OPA-627 and AD-8610, I wonder how many would manage to tell the difference in a properly conducted blind test 
	

	
	
		
		

		
			











 [edit]
 Natually, I'm assuming that both would be used in a circuit where the output measurements are similar and sufficient, such as distortion below what are considered audible levels, etc.


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## fewtch

Quote:


 _Originally posted by Prune _
*Regarding ppl's statement concerning how most would differentiate between the sound of OPA-627 and AD-8610, I wonder how many would manage to tell the difference in a properly conducted blind test 
	

	
	
		
		

		
		
	


	








* 
 

People don't typically listen to their equipment under the conditions of a formal blind or double-blind test, so does it really matter? You set up an artificial context for a test that doesn't mimic the way people listen in real life, will that test say anything of real importance? Maybe, maybe not...

 BTW (and FWIW) I'm neither an objectivist nor a subjectivist... I like to think in terms of looking at things as a given situation calls for it, rather than holding beliefs that may be true under a certain set of conditions and false under another. Sometimes objectivity and objective measurements come in handy (and when they do they make great tools), but in other situations it's like trying to fit square pegs into round holes. I've found that measurements can be a big help to ears in areas where they're weak, and ears are important in areas where measurements don't seem to give the whole picture. 

 IMO, "measurements only" (the map is the territory) tends toward bad sound, and "ears only" (maps are never helpful) tends toward superstition and wasting money. Just my 2 cents...


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## Prune

The hell with test conditions: my point is, can you tell the difference when you _don't know_ which one is in? Because if you can't, then they indeed sound the same as measurements would suggest, and your psychological bias is the _only_ thing that makes a difference. 
	

	
	
		
		

		
		
	


	



 Here's a simple way to check if you have two amps: very carefully match levels with a multimeter, then get a friend and turning your back to him, ask him to unplug the amp and then randomly either swap it or plug the same one back in, and then see if you can tell if it was changed or not. Or, if you want fast switching, then use a rotary selector. Do this ten times or so and then see if your guesses were right sufficiently more than 50% of the time, else it was random guessing. How much is sufficiently more depends on the number of trials.
 Some things indeed sound different, but also a lot of differences simply disappear in a proper blind test. And if you can't hear the difference between two things in a system where the rest of components have really high resolution so the maximum differences should be clear, then why not save money and use the cheaper one? Otherwise, it's just a fetishism for fancier gear, simple as that!


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## fiddler

Quote:


 _Originally posted by Prune _
*Regarding ppl's statement concerning how most would differentiate between the sound of OPA-627 and AD-8610, I wonder how many would manage to tell the difference in a properly conducted blind test 
	

	
	
		
		

		
			










* 
 

 Sure, I think I'd be able to pretty easily. Might even be able to do it with interconnects. No, I'm not shy about my fantastic ears. 
	

	
	
		
		

		
		
	


	




 Oh, and explain me this: I had my girlfriend listen to a couple interconnects (she's a violinist too), and asked her what differences she could hear. I didn't tell her which one was supposed to sound better, I didn't tell her which one was supposed to sound warmer or brighter or whatever. Someone with very little knowledge about audio, but with very good ears. She made similar observations as my own, and this was just after a quick listen (comparing a couple 1 minute clips). These were two cables that should have sounded the same according to measurements. I.e., neither were bad enough to have capacitive HF roll-off in the audible range, etc. etc... 

 It's just like the Stradivarius mystery, nobody really understands why it sounds better-- people have attempted to make exact replicas, and they just don't sound nearly as good! Maybe it's the age, maybe it's the wood, the varnish, nobody knows.


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## Prune

Uh, the way I read this is that violinists have superhuman hearing. I guess mere pianists like myself must be completely tone deaf...

 This discussion reminds me of how in psychology introspectionism became a failed approach. But then again, psychology is a science


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## fiddler

Quote:


 _Originally posted by Prune _
*




 Uh, the way I read this is that violinists have superhuman hearing. I guess mere pianists like myself must be completely tone deaf...
* 
 

I'm glad you're learning! 
	

	
	
		
		

		
		
	


	










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)


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## usc goose

Quote:


 _Originally posted by Prune _
*I guess mere pianists like myself must be completely tone deaf...
* 
 

i believe it. my old roommate was a bachelors of music piano performance major at usc. i taught him guitar and watching him change tunings was just frustrating. couldn't find, name or match a pitch to save his life. 

 he was a ridiculously talented piano player though.

 edit: rolling ad8620 vs opa637 in my meta42 is not too subtle a difference at all to my ears either. i was originally trained as a singer. (also guitar, piano, bass, drums, and very very ugly trumpet)


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## Prune

Hmm, in that case, now that I'm trying to learn the organ, I suppose I can expect to loose any sense of pitch whatsoever


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## ppl

Adding to the info contained in this thread I add the Scots Guide to Electronics in particular the Audio analog section. This site contains easy to understand analog design concepts in a semi technical easy to understand language. 
http://www.st-andrews.ac.uk/~www_pa/...io/Analog.html

 the animated gif depicting the Class of amplifiers allows instant visulization of how this actualy works as a system
http://www.bcae1.com/ampclass.htm


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## Sycraft

Well I personally don't dismiss subjective tests for the simple reason that we do not know that we are objectively measuring everything that is important to human hearing. Like say the way in which a signal is distorted. Maybe one amp distorts a signal differently than another, despite both having the same measured level of distortion. So it is possible we hear things that just don't show up on the tests we conduct.

 However, I have studied a lot of Psychology and I do know the power of suggestion and the mind's ability to fool itself. My favourite experiment along these lines, which I can't find a link to despite my best efforts, was one allegedly conducte don speaker wire, really on the power of suggestion and peer pressure. They had a room with expert listeners in it and put a nice audio setup. They then introduce the three wire candidates, two high end cables, and normal braided copper wire, for reference. They would then play a peice of music on each, with assistants switching the wire in between each replay.

 Well opinons disagreed about which of the two high end cables was best, but the experts were united that both sounded far better than the copper wire. The catch? The wires were never chainged, it was normal copper wire the whole time. All percieved changes were just in the mind of the listener.

 Now this isn't proof that different wire doesn't matter (that wasn't tested), but it IS proof (or rather one study in a line of proof) of the power of the mind.

 What I'd like to see more of is stuff you deal with in psychology all the time: proper blind experiements. However I also want to see them done properly. The problem is, you can't really ask someone reliably to tell if they like something in a quick A/B test. They need time to listen on a wide variety of material, espically if the change is supposed to be subtile.

 It's something I'd like to try with something like a PPA sometime, and maybe will. Build two amps with just razor fine tolerances on everything, and have different opamps in them. Then, put them both in identicle boxes, rigged to be tamper resistant. But a label A on one box, and B on the other, randomize which box is labeled which. Give them to test subjects for a good period of time, a couple days at least. Let them go back and forth all they like. When their time is up, take back the boxes and ask which was better, or no difference and WHY they liked it better. See what kind of result you get.

 If the subjects have no idea what the variable is, and there is no way for them to find out, then you have a pretty good chance of getting a real, unbiased opinon. Then you can see if there's any trends in what people like and, more importantly, why they like it. Just because the like results are 50/50 doesn't mean no difference was heard, it might just be different preferences. However if there is no corrilation between why somethign was liked, probably people are just making things up (since most will figure they are supposed to hear a difference, maybe as a control give some subjecst two idnenticle amps). However if you see real correlation between a given opamp and a given reason for liking it, you probably have a real difference, and can then maybe try and measure it.

 Thing is, empirical tests of subjective data are TOUGH to properly design and execute, and there seems to be little intrest in teh audio industry to find out what they might reveal. If they show it's all in your head, all the audiophile firms are screwed. If they show there is osmething going on, all the pro firms are screwed. Either way you have something many people don't want to hear.

 Personally, I hope to maybe do graduate research on the topic someday, but I'm not sure that will be feasable. It would take a fair bit of money to organise something like that, and I imagine grants for that sort of thing are hard to come by.


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## Prune

Dude, the argument here is exactly the one between those who accept scientific blind tests as the main practical window to The Truth(TM) and the fools that do not, so they can justify their hi-fi equipment fetishism. I use silver wire and Auricaps and Caddock MK132 resistors, but at least I don't pretend that I could actually hear a difference (nor would most of the self-proclaimed golden ears; if you come across them in real life, it's always fun to challenge them to a blind test and embarass them 
	

	
	
		
		

		
		
	


	




 ).


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## Sycraft

But here's the thing: Currently, the empiricists (of which I am one, have my copy of The Logic of Scientific Discovery and everything) rely almost exclusively on scopes, FFTs and so on. Objective measurements, in other words. The reason is because we know that people lie, and even when they don't their perception isn't absolute. Measurements are, my scope never lies to me (provided it's calibrated).

 Ok, great, however what we empiricists do NOT know is if we have discovered everything that is important to human hearing. We know frequency response is, so we measure that. We know noise is, so we measure that, etc. But, what if there is a property we DON'T measure, beacuse we aren't aware of or believe it is unimportant, that is important to perception? Well that would mean, despite our claims that two things sound the same because they are identicle on the scope, we are wrong.

 One possible example would be the nature of distorion. All I ever see measured is the amount, never the kind. I don't know enough about audio distortion to say for sure, but I would infer that distortion does not distort all harmonics of a note evenly. Thus the distortion itself will have a harmonic shape, just as the note does. The difference between a trumpet at A440 and a claranet at A440 isn't the pitch, the fundimental is 440Hz in both cases. Nor is the difference in the frequency of the harmonics, they are all integer multiples of 440Hz. The difference is in the relitive amplitudes of the harmonics, which are loud, which are soft. THAT is what makes sound to a human, and how we identify speech and so on.

 So, maybe the shape of a device's distortion (if indeed distortion has a shape as I postulate) is something that effects our perception. We hear two things with the same THD, but one has a shape that sounds better than the other.

 I'm not saying this is for sure that it exists or if it does that it matters, I am simply using it as an example of something that we do not attempt to measure and figure out what is good and bad.

 Well, rather than just chase my tail around, the research I think would be interesting to do would be to take two things that are widely regarded to have good, but different sound that ought not, like the op amps, and do a proper, multi-level test on them. If the study shows that there probably IS a difference in sound, I'd then want to do more research to try and find out what causes that difference.

 Or maybe (more likely I believe) I'll find that there IS no difference. In that case, we have some real, valid, empirical evidence to argue that. Claiming "it's all in your head" when you don't have evidence of that is kind of going out on a limb. It's probably all in our heads, but we need to do more testing to validate that hypothesis.

 I've been mulling this one over and I might see if it's something that some funding and facilities could be gotten for. Need to hash out the design better first though. It's an interesting topic that is pretty much absent from the psychological journals.


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## Prune

Quote:


  Originally Posted by *Sycraft* 
_Ok, great, however what we empiricists do NOT know is if we have discovered everything that is important to human hearing._

 

Of course measurements do not reflect everything that may affect perception. After all, distortion figures are but summary statistics, and don't tell you the detailed profile of the distortion, which also matters to perception besides the magnitude of the distortion. Again, this is not at issue. A properly conducted blind test covers all known and unknown matters of perception. Denying this is denying rationality and science as a way to understand the world -- it turns into a religion.

 I've said this several times at the various audio forums: by far the greatest difference between live sound (and I listen to live classical and jazz concerts extensively) and electronically reproduced one is in creating a proper soundstage, which is to some extent a geometric problem, and includes the recording arrangement's ability to record the proper directional distribution of sound, and the reproduction at the other end of such directionality in a way that parasitics are eliminated. By parasitics I mean things such as room reflections and more importantly, sound intended for one ear reaching the other ear, which is not a problem with headphones but it is a problem for speakers. Generally, stereo separation is crudely increased in the recording in order to accomodate for this crosstalk, but the results are not life-like (and worst for headphones). The proper way to deal with this is signal processing and speaker arrangements which can eliminate most of the crosstalk (there are numerous examples of related research that can be found on the web). This way binaural recordings can be listened to properly with speakers. But those have limitations too, such as different HRTFs (head related transfer functions) on the recording head or dummy head, and the listeners head/ears, which makes especially up/down and front/back positioning less effective than if the same shape head/ears were used (again, perhaps signal processing can accomodate for this if the listener's HRTF is known; imagine everyone getting it measured and feeding it into the signal processor as a custom profile 
	

	
	
		
		

		
		
	


	




 ); etc. etc.


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## Prune

I'd like to hear comments on D Self's article at http://www.dself.dsl.pipex.com/ampin...o/subjectv.htm


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## chuao

Personally, I think Doug Self represents a radical extreme in the objectivist camp, and he's putting his evidence through a contradictory-fact-removing-filter worthy of Fox News. I don't have the listening experience to judge any of his conclusions, but I can certainly critique his logic.

 Overall, his book seems to have one underlying theme: "I think all amplifiers sound the same, but some people don't, so here's how you can swindle more customers by advertising a really low THD measurement that you and I both know doesn't make a bit of difference." So should it surprise us if his arguements don't hold much water?

 The most obvious rebuttal to objectivism is just that amplifiers are bulit for listening, and all that matters in the end is the subjective perception of the listener. Perhaps in Futurama they could have a THD-analyzing robot that loves nothing more than to listen to beautiful undistorted sine waves, but that's not me.

 Which brings us to another clear mistake: his near-total reliance on THD measurements as the final word on amplifier quality. In Part 1 of this article:

http://peufeu.free.fr/audio/memory/

 you can see a great example of where THD measurements specatcularly fail to predict the behavior of the system. What Self really needs to remember is that distortion residuals will fully characterize a memoryless nonlinear system, and the various linear ODE tools (state-space, Laplace, Fourier) will fully characterize an LTI system. But to analyze a real amplifier which is neither memoryless nor linear, none of those tools are theoretically appropriate. In fact, there IS no general theory that allows one to analytically predict the behavior of such a system. Even proving stability requires you to "guess" a Lyapunov function.

 Another fatal flaw is his lack of respect for human hearing. It's true, we can only percieve a 10% step change in amplitude or a 0.2% step change in frequency, but those measurements have little to do with how we actually use our hearing. We can nevertheless perform a myriad of feats that not even the best microphones and DSP algorithms can match...like picking a voice we recognize out of a room full of people. Also relevant is the fact (which I unfortuneately know only from anecdotes) that a difference in volume that's not directly perceptible will nonetheless make a louder amplifier sound better.

 So to conclude, I don't disparage mathematical analysis as a way to better sound quality...it's just essential to have the right tools. Doug Self does not have those tools, and furthermore he seems to have given up looking.


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## Prune

Quote:


 The most obvious rebuttal to objectivism is just that amplifiers are bulit for listening, and all that matters in the end is the subjective perception of the listener. 
 

Yes, and it is what a blind test measures (there are even used in psychology, after all). This is one of the things that bothers me most, why do publicized blind tests show a spectacular failure of distinguishing between amplifiers? Likewise for the subtraction tests -- if you can't hear a residue, then how could there be audible distortion? There simply is no rational argument against blind testing. Some argue that a nil result doesn't prove there is no difference, which is true, but statistically over a number of trials the likelihood that there is a difference can become vanishingly small.

  Quote:


 http://peufeu.free.fr/audio/memory/ 
 

Yes, I've seen this before, but not heard much discussion about it.

  Quote:


 We can nevertheless perform a myriad of feats that not even the best microphones and DSP algorithms can match...like picking a voice we recognize out of a room full of people. 
 

Part of that trick has to do with directionality. It's much much harder to do with a mono signal. The rest of the process is indeed DSP, although implemented in wetware instead of silicon.

  Quote:


 Also relevant is the fact (which I unfortuneately know only from anecdotes) that a difference in volume that's not directly perceptible will nonetheless make a louder amplifier sound better. 
 

Yes, it is very important in blind tests that levels are properly matched. But if just a slight difference in volume can mask other issues, doesn't that make them insignificant?

 One thing that Self left out is the issue of imaging. The ear can distinguish clicks as separate even if they are at a rate above 20 kHz.

 The only rational objection I came up with regarding this article was his discussion of phase. Apparently he is unaware that phase is an important component of directional perception; though, on the other hand, with most speaker setups it's already messed up enough so that the amplifier is the least offender in that respect.
 Also, on the Crossover Design page ( http://www.silcom.com/~aludwig/Sysde...ove_Design.htm ), it is mentioned that ears can still hear clicks occuring at a rate faster than 20 kHz as distinct (in the Transient Response section of the page, though the server is down at the time of writing, but you can use the Google cache). Which leaves me wondering whether amplifier blind tests would have more positive results in a setup where phase distortion from the speakers and room reflections are eliminated (that still leaves crosstalk to mess up the imaging, however, so using headphones with a binaural recording would be better, even though headphones do not present a realistic load to a power amp).


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## chuao

Ok, maybe I should get more specific. To start with, here's one of the claims of subjectivism Self claims is false:


> Degradation effects exist in amplifiers that are unknown to engineering science, and are not revealed by the usual measurements.


In fact, this statement is obviously true. It's essentially an axiom of the scientific method. It's hubris to assume that we've uncovered EVERY distortion that nature put into the amplifier, so of course, there will be some we haven't discovered yet. The burden of proof is therefore on him to show that these unmeasurable distortions don't change the subjective perception of quality. Instead, he assumes that they simply don't exist.

 So, if Doug Self has assumed from the beginning that there is no such thing as a distortion mechanism that doesn't show up on his Audio Precision System 2 or whatever, why should we treat it as significant that he doesn't find any?

 For instance, here's what he says in his rebuttal to the claim that amplifiers can't be completely characterized with just sine waves:


> You must remember that an amplifier has no perspective on the signal arriving at its input, but literally takes it as it comes.


That's quite false. Since amplifiers are not memoryless, their internal state DOES depend on the past history of the music, and since they're nonlinear, other parameters like the gain and distortion spectrum do depend on the previous signal. Sine waves are an easy test of an amplifier because they're _periodic_, and thus admit a steady-state solution in which all transient behavior has died out.

 Slew rate limiting is an obvious example: if you crank in a step that causes slew rate limiting to kick in, other signals will be silenced entirely until the ramp is done, since the input stage is saturated.

 This interaction between linear and nonlinear effects is also the crux of what peufeu is talking about, and his research (along with Lavardin's) clearly shows a potential mechanism for audible distortion that doesn't show up on a THD spectrum. Listening tests (maybe not blind ones) show a very obvious difference from this new effect.

 Now, I've never heard a "blameless" amplifier so it may be that its distortion is too low to begin with for any of this to matter, but it does not change the fact that Self's reasoning is wrong.


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## chuao

Sycraft's comments here are right on the money, in my opinion. He's basically saying the exact same thing I am:

  Quote:


 Ok, great, however what we empiricists do NOT know is if we have discovered everything that is important to human hearing. We know frequency response is, so we measure that. We know noise is, so we measure that, etc. But, what if there is a property we DON'T measure, beacuse we aren't aware of or believe it is unimportant, that is important to perception? Well that would mean, despite our claims that two things sound the same because they are identicle on the scope, we are wrong. 
 

Also, I think he's got a great point on blind tests:

  Quote:


 Build two amps with just razor fine tolerances on everything, and have different opamps in them. Then, put them both in identicle boxes, rigged to be tamper resistant. But a label A on one box, and B on the other, randomize which box is labeled which. Give them to test subjects for a good period of time, a couple days at least. Let them go back and forth all they like. When their time is up, take back the boxes and ask which was better, or no difference and WHY they liked it better. 
 

So, when you get some blind tests that were done that way, then it will really show something. It's really common for some little flaw to creep up after a few days of listening that just makes it fatiguing and unenjoyable, making most types of blind tests regrettably impractical.


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## Sycraft

Ya, chuao, basically what I'm saying is that many (most) objectivists are discarding proper empiricism. In modren empiricism, you realise that you do not prove something true with an experiment, you just show it to be not false in that particular case. The most examples of not-false tests you have, the more sure you can be that your theory is true. We are quite sure the theory of gravity is true since it's been tested millions of times in different ways. We are much less sure about superstring theory, as it still has yet to stand to any real tests. We are not sure about the theory of the mind, since evidence is contradictory.

 Theories, no matter how well seeming, can be disproven. A Biggie was parity conservation in physics. An absolute tennant of subatomic physics for a long time was the concept of parity, that is that two physical systems, one of which is a
 mirror image of the other, must behave in identical fashion. Well turns out this ISN'T the case, even though it seems ot make a great deal of sense and all scientists believed it to be so. Pairty violation has been experimentally demonstrated on many occasion since it's discovery.

 I think that with audio, empiricsts are too sure of themselves that everything that is relivant to human hearing has been discovered. From what I've read on it, results are inconclusive. There are tests that show people can't hear anything, tests that show they can, and many that produce no useful data. At this point I think it is premature to claim that we are capable of accurately reducing sound quality to a set of numbers.

 If I decide to go to grad school, I may try and do research on this topic, but I think for now it's incorrect to state that we can objectively measure everything important to sound quality.


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## Prune

Quote:


 you do not prove something true with an experiment
 ...blah blah blah...
 Theories, no matter how well seeming, can be disproven. 
 

Well duh, that's by definition. That's why religion is ********, because it's unfalsifiable. But, that does not mean that we do not accept our theories when trying to apply them practically.
  Quote:


 We are not sure about the theory of the mind, since evidence is contradictory. 
 

In my studies in cognitive psychology and neuroscience I have encountered various theories attempting to explain different aspects of the mind, but most certainly no claim for an overall theory of mind, so your statment is pointless. How can there be contradictory evidence to something that doesn't exist?
  Quote:


 An absolute tennant of subatomic physics for a long time was the concept of parity
 ...blah blah blah... 
 

Of course mistakes happen. But it is impractical to assume the major theory of the day is incorrect. Example: I could assume quantum theory overall is wrong, and decide not to rely on anything derived from it, specifically any and all semiconductor electronics. That would be indeed preposterous. Despite all talk of major paradigm shifts and turning points in science, there are no such in the physical (that is, fundamental, because all others reduce to them) sciences. Overall, what we have are further and further refinements of our models of the world, almost asymptotic to whatever level of 'truth' may be reachable by our cognition. We still use Newton's laws, after all. How many physicists (Penrose notwithstanding) doubt that any future accepted base theory will not be quantum in nature?
  Quote:


 I think that with audio, empiricsts are too sure of themselves that everything that is relivant to human hearing has been discovered. From what I've read on it, results are inconclusive. 
 

I would love for you to show me peer reviewed references where valid results of blind tests have shown a difference is audible when accepted theory says it wouldn't have been.
  Quote:


 I think it is premature to claim that we are capable of accurately reducing sound quality to a set of numbers. 
 

The laws of physics are computational (again, Penrose's ramblings notwithstanding *). The brain is a part of the physical universe. Therefore, the brain and it's actions (mind) are computational, and thus not only reducible to numbers, but to finite precision rational numbers at that. Like it or not, all your thought sequences can be mathematically mapped to a finite automaton **.

  Quote:


 If I decide to go to grad school, I may try and do research on this topic, but I think for now it's incorrect to state that we can objectively measure everything important to sound quality. 
 

Your "for now" clause is subject to the "If I decide to go to grad school". I hope that is accidental, else you are saying that we should all assume "it's incorrect to state that....", at least until you go to grad school. What arrogance!


 (I can provide PDF files for any of the following if you can't find copies; sorry for the lack of proper citation format, but this is just a forum after all)

 * A number of rebuttals have been published, but the most precise is
_A Refutation of Penrose's Godelian Case Against Articial Intelligence_

 ** Especially
_Why I am not a Super Turing Machine_
 Also see
_Cognition and the Computational Power of Connectionist Networks
 Turing vs Super-Turing
 Universal Limits on Computation
 Fundamental Physical Limits on Computation
 Undecidability Everywhere
 On the Computational Capabilities of Physical Systems_


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## Sycraft

Chill dude, I'm not saying I'll be the guy to solve this. You are way too emotinally involved here. I'm simply mentioning that this is something that intrests me and I might study.

 As for theories of mind, I can name two big ones, and if you clim either has proof as being the theory mind, I can prove you wrong in about 6 seconds:

 1) DCTM, Digital Computational Theory of Mind. This is the theory that the mind works something like a digital device where is processes data in sequence to get a result and is composes of multiple dedicated subsystems.

 2) CCTM Connectionist Computational Theory of Mind. This is the theory where the mind works like an weighted neural network, that individual units have no data or processing ability in and of themselves, but the overall network processess data to get the desired result.

 Both theories have some merit, though ti seems the mind is generally more connectonist than digital. However regardless, neither is completely correct. For more info see Harnish, Robert M. (2002) Minds, Brains, and Computers, specifically chapters 8, 9, 12, and 13.

 As for citations to experiements that are inconclusive or show people able to hear difference in blind tests: If you are truly interested, I'll gather citations, though I do not have them on hand. Regardless, most tests that were done and claim to show no perceptable difference can be challenged as being done improperly. As I meantioned, a quick A/B test might not be sufficient to determine perceptable difference. Perception is complex. You can notice your name spoken in a noisy room with no effort but not so for random other words. All tests that I am aware of that show no difference were done in classic, highly limited A/B style.

 So the thing is, theories that are equaly probable given the evidence provided can be advanced. As such you shouldn't put too much stock in to the theory that we currently do objectively measure all that is important to perception. I'm not saying to dismiss it outright, but trying to hold it up as truth is a little premeture, it really doesn't meet the standard of strong inference. For more information refer to Popper, Karl (1959) The Logic of Scientific Discovery.


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## Prune

Quote:


 You are way too emotinally involved here. 
 

And this follows from exactly what that I wrote?
  Quote:


 As for theories of mind, I can name two big ones 
 

These 1) and 2) are more helpful analogies than precise theories, and clearly neither is truly the case, the same way that quanta are neither particles nor waves, and we simply use these analogies as they are the closest things that we have sensory experiences with in the macro world. What is the case, however, is that the brain's main evolutionary function in an organism is an information processing device (that is what cognitivism is all about), and so information theory/physics lets us derive severe limits on the mind, regardless whether you are working within the frameworks of analogies such as 1) and 2).
  Quote:


 As for citations to experiements that are inconclusive or show people able to hear difference in blind tests: If you are truly interested, I'll gather citations 
 

My frustration in finding such is the _raison d'etre_ for much of my posts in such threads.

 BTW, do you perchance post on Slashdot under a similar alias?


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## Sycraft

Quote:


 BTW, do you perchance post on Slashdot under a similar alias? 
 

All the time and everywhere I am Sycraft. On Slashdot, I append a suffix since I created an account and lost the password and e-mail address to get it back.

 As for the theoris of mind, there are many philsophers that take one or the other seriously. None of them claim it ot be a total explination, but they claim it to be basicallly correct. As, at this point, there is evidence for and against both theories, we can say that there is no one to accept or believe as per strong inference.

 I believe we have a similar situation with audio. Subjectivists claims there are things you can hear that are not yet measured without adiquate backing, objectiviststs claim that we can measure everything without adiquate backing.

 As for your sig, philsohpy is notquestions that cannot be answered, at least not good and useful philsophy. Philsophy is reasoning out things so that they can be tested by science. I'll again turn to theroies of mind and language, since that is what I've studied the most. The DCTM and CCTM are useful philsophical theories in that they give psychologists a model to test. The philsopher postulates hwo the mind might work, the psychologist can then test it. Same thing in psycholingustics. You can't test how humans deal with language until you have a model to test. Philsophers generate the model, psychologists falsify it.


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## Prune

I have never heard anyone define philosophy the way you did. It is not the job of the philosopher to postulate scientific theories, it is the job of the scientists to both do that and test them -- thus the distinction between theoretical and experimental scientists in some theories (especially physics). Physics theories are generally born in the minds of theoretical physicists, not philosophers. In regards to science, philosophy concerns itself with metaphysics, ontologies, etc., defining what science is, how its methods can be rationally justified, and just what scientific results actually mean. Doing the science is left to the scientists.


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## ppl

This link has some interesting thoughts on Distortion along with some wav. Files you can Down Load and listen to on your own Rig. These are musical excerpts containing specific amounts of added distortion.
http://www.gedlee.com/distortion_perception.htm


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## taymat

Quote:


  Originally Posted by *Sycraft* 
_But here's the thing: Currently, the empiricists (of which I am one, have my copy of The Logic of Scientific Discovery and everything) rely almost exclusively on scopes, FFTs and so on. Objective measurements, in other words. The reason is because we know that people lie, and even when they don't their perception isn't absolute. Measurements are, my scope never lies to me (provided it's calibrated).

 Ok, great, however what we empiricists do NOT know is if we have discovered everything that is important to human hearing. We know frequency response is, so we measure that. We know noise is, so we measure that, etc. But, what if there is a property we DON'T measure, beacuse we aren't aware of or believe it is unimportant, that is important to perception? Well that would mean, despite our claims that two things sound the same because they are identicle on the scope, we are wrong.

 One possible example would be the nature of distorion. All I ever see measured is the amount, never the kind. I don't know enough about audio distortion to say for sure, but I would infer that distortion does not distort all harmonics of a note evenly. Thus the distortion itself will have a harmonic shape, just as the note does. The difference between a trumpet at A440 and a claranet at A440 isn't the pitch, the fundimental is 440Hz in both cases. Nor is the difference in the frequency of the harmonics, they are all integer multiples of 440Hz. The difference is in the relitive amplitudes of the harmonics, which are loud, which are soft. THAT is what makes sound to a human, and how we identify speech and so on.

 So, maybe the shape of a device's distortion (if indeed distortion has a shape as I postulate) is something that effects our perception. We hear two things with the same THD, but one has a shape that sounds better than the other.

 I'm not saying this is for sure that it exists or if it does that it matters, I am simply using it as an example of something that we do not attempt to measure and figure out what is good and bad.

 Well, rather than just chase my tail around, the research I think would be interesting to do would be to take two things that are widely regarded to have good, but different sound that ought not, like the op amps, and do a proper, multi-level test on them. If the study shows that there probably IS a difference in sound, I'd then want to do more research to try and find out what causes that difference.

 Or maybe (more likely I believe) I'll find that there IS no difference. In that case, we have some real, valid, empirical evidence to argue that. Claiming "it's all in your head" when you don't have evidence of that is kind of going out on a limb. It's probably all in our heads, but we need to do more testing to validate that hypothesis.

 I've been mulling this one over and I might see if it's something that some funding and facilities could be gotten for. Need to hash out the design better first though. It's an interesting topic that is pretty much absent from the psychological journals._

 

You are completely right. There are many different types of harmonics and they all have slightly different effects on how we percieve the reproduced sound. For example it has long been know that odd harmonics are more pleasing to the ear than even harmonics. THD figures mean little, although it's arguable that we can still hear/feel the effects of in-audiable harmonics on sound in the audiable range, much more porgress would be made if the main types of harmonics were measured individually.


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## Prune

Quote:


  Originally Posted by *ppl* 
_This link has some interesting thoughts on Distortion along with some wav. Files you can Down Load and listen to on your own Rig. These are musical excerpts containing specific amounts of added distortion.
http://www.gedlee.com/distortion_perception.htm_

 

The presentations are very interesting. For those that didn't RTFA, they define a new metric (the AES presentation) which uses weighting dependent on the masking of the human ear. Unlike the THD/IMD measures, this is a measure of the perceptability of a distortion. With further experiments the metric can be tuned to better represent human perception of nonlinearities.

 However, I am willing to bet that if this metric was adopted by the audio community as a THD/IMD replacement, it will still be rejected by the subjectivists just like any other piece of science and rationality that has shown that their 99.999999999999999999% pure silver wiring doesn't make a damn bit of difference.

 On the other hand, the proposed metric has a significant shortcoming in that it assumes the nonlinearities are frequency independent, which, as they point out, does not hold in the case of speakers. As speakers are the most distorting mechanism in the audio chain (other than potentially the recording, but that we do not have control of), they are the ones most needing something like this. But we already know that ESL and plasma are the best drivers. My secret daydream is that Dr. Hill will follow up his original creation with full range drivers, and without the helium tank 
	

	
	
		
		

		
			





 BTW, what happened to Sycraft, did he run off or what?


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## ppl

more links to think about 
http://www.tpub.com/content/neets/14...s/14182_33.htm
 Voice Quality
http://www.tpub.com/content/photogra.../14129_262.htm
 Acoustics 101
http://www.tpub.com/neets/book10/39f.htm

 PROPAGATION OF LIGHT
http://www.tpub.com/content/neets/14...s/14182_37.htm

 Acoustics in the market place and out of the Lab
http://world.std.com/~lyoncorp/techb...rticle3_03.pdf
http://www.agr.kuleuven.ac.be/aee/am...c/SQparams.pdf

 A method for optimizing percept sound quality of an audio system,
http://www.finalinvention.de/HTML/PAPER.html

 MP3 Encoder Tests
http://arstechnica.com/wankerdesk/1q00/mp3/mp3-1.html
 from this link is the following
 “Numbers can only tell you so much. Trying to choose an MP3 encoder by measuring its bandwidth and waveform MSE is like trying to choose a car by only clocking its 0-60 mph”
 MP3 Encoding Modeling The history of MP3 encoding and Napster are also covered nice historical look since the article is dated in the late 1980’s
http://ntrg.cs.tcd.ie/undergrad/4ba2...oup10/mp3.html


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## Prune

Regarding the link about light, a) what does that have to do with anything? and b) statements there such as "The exact nature of light is not fully understood, although scientists have been studying the subject for many centuries." are plain wrong. Explaining light was one of the first successes of quantum theory many decades ago. The wave/particle duality is a non-issue, since quanta are neither waves nor particles, but things for which we have no analogues in the macro world we sense, and thus cannot relate to directly. That's what the math is for.

 Regarding audio codec listening tests, here's the link I recommend:
http://www.rjamorim.com/test/
 This guy did the tests by having many people download the setup (an ABC/hidden reference blind test software and sound file set) and perform the tests on their own computers, then send back the results (encryption to prevent cheating).


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## ppl

Prune Why the hostility my intent hear is not to take sides or provoke an argument. I just to stimulate thought on this subject regarding the Light theroy as you allready know the human brain process Sight in a similer way to hearing. unless this theroy has changeged in 20 years.


 thanks for the alternate link more info is always better


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## Prune

You are seeing hostility where there is none.

 I do not at all agree that the brain processes light and sound in a similar way. An enormous portion of our brain is devoted to vision, far more than to sound. Aural perception is fundamentally different because the information is in the 1D time domain, whereas vision is more in the 2D/3D space domain (motion is just one small part). The relationships between the two sensory modalities and the various types of memory are also very distinct (for example looking at the phonological short-term memory loop vs. the visuo-spatial short-term memory, etc.). And so on.

 Regarding music perception specifically, a good site is this one for a music psychology course, with notes accessible from the menu:
http://www.ethnomusic.ucla.edu/cours.../172Frames.htm
 Though web resources are no substitute for a good book. I've heard good things about _Cognitive Neuroscience of Music_, but my "to read" queue is long enough as it is...


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## ppl

Hi Puune
 Thanks for the Link too bad the files are in real audio a player I will never install on any windows computer I want to have working properly.

 Anyway human perception is not my field of expertise however the vision part I mentioned was from an old AES report. It’s more that 20 or so years old and I am sorry my recall is just not so good after 20 years. Basically true vision occupies more resources in the brain that audio and vision is given precedence. However if I remember correctly the ear can perceive the location of a sound to within 1 degree is this correct?

 what is your take on the following 

http://www.hometheaterhifi.com/volum...enitz1097.html
http://www.milbert.com/tstxt.htm

 also the soon to be revised DVD performance BenchMark
http://www.hometheaterhifi.com/volum...io-9-2000.html

 soundstage in the home vs the recording studio 
http://forum.ecoustics.com/bbs/messages/5/62252.html

 Cal tech Music lab
http://www.its.caltech.edu/~musiclab/pq-experiment.htm

 Sound reinforcement
http://www.tele.ntnu.no/akustikk/mee...99/landone.pdf
http://www.elec.qmul.ac.uk/dafx03/pr...dfs/dafx26.pdf
http://www.iptel.org/2001/pg/final_program/Gierlich.pdf


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## Prune

Real's crap is easy to deal with: once you install, go to the Run sections of the registry and remove all Real related items. This way it will only have its software loaded when you are actually using it, instead of loading parts at startup and running in the background.

  Quote:


 However if I remember correctly the ear can perceive the location of a sound to within 1 degree is this correct? 
 

Not with the phase distortions of common speaker/room setups.


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## ppl

this link tends to indicate 1.5 deg for a Mil ECM system and 5 deg for human hrearing. http://www.silcom.com/~aludwig/EARS.htm


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## drewd

Over at Audio Asylum's Critic's Corner, there is always a pretty spirited "measured versus perceived" argument going on. Kalman Rubenstein, one of the Stereophile reviewers, posted a link to Stereophile's web site that has a huge number of links to articles within that site covering audio measurements, how they might relate to perceived differences in components and how to interpret measurements (particularly aimed at John Atkinson's measurements). I've only just started wading through them, but what I've read seems pretty balanced with regard to the relevancy of measured data. Even if you just skim over one or two of the articles, you'll probably find something that is interesting and informative.

http://www.stereophile.com/searchres...=3&cs=&stype=A

 -Drew


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## gaboo

This article deals mainly with differences between equalizers. But, it touches a very interesting point in the subjective/objective debate: some specific types of very small distortions in the order of 0.1dB and 1/100 radians were proven audible.


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## Prune

Damn, this is the best find on this thread this far.


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## Prune

But what crossover can avoid all such colorations? Does this mean that multiple driver speakers are doomed to be colored unless high-resolution digital crossovers are used, with the given multiplication of DAC-to-speaker paths?

 One interesting crossover I was looking at is this one:
http://www.geocities.com/kreskovs/Crossoverdoc.html
 Other good discussion here:
http://www.silcom.com/~aludwig/Sysde...ove_Design.htm

 I already have one capacitor in the signal path (DC blocking) in my DAC. This causes some phase non-flatness at the frequency extremes. However, I have read that a) when looking at it graphed as group delay, it's only important to be flat above 100 Hz or so, and b) continuous and smooth curve is important, not just the flatness. Discontinuities are very audible, which tends to fit with the article gaboo found.

 I have heard hifizen's (from diyaudio) tube speaker amp, which is not even OTL, and it has an even less flat phase, yet it sounds quite nice. That either means the specific phase non-linearity is not very audible, or that it's the kind of distortion that may be called, er, euphonic coloring. However, I did not get a chance to evaluate it for imaging, where phase is very important (though again, not in the low end). Of course, most recordings already screw up imaging; in the end only binaural recordings with headphones, or complex crosstalk cancellation processing in specific speaker setups can really reproduce it properly, so the playback system's faults will not be apparent.


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## gaboo

#include <disclaimer for possible thread crapping>

  Quote:


  Originally Posted by *Prune* 
_Damn, this is the best find on this thread this far._

 

Here are a few more articles by the same author, Michael Gerzon, not necessarily related to the thread topic though.


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## ppl

Yes this shows how previously accepted theory are later shown to be less that correct however I maintain still useful for study,
 See Toole, Floyd E., "The Acoustics and Psychoacoustics of Loudspeakers and Rooms - The Stereo Past and the Multichannel Future," 109th AES Conv., Los Angeles, Sept 2000. 
 Lip****z, Stanly P., Pocock, Mark, and Vanderkooy, John, "On the Audibility of Midrange Phase Distortion in Audio Systems,' J. Audio Eng. Soc., Vol. 30, No, 9, Sept. 1982, pp 580-595.

 Dr Lip****z in particular attempted to debunk any and all subjections about measurement vs. perceived sound quality differences with his own radical theories on the how and the why of Audio quality and test and measure. Further reading is at http://www.silcom.com/~aludwig/Phase_audibility.htm
http://www.auditory.org/mhonarc/2002/msg00524.html
http://www.linkwitzlab.com/phs-dist2.htm

 Some Interesting stuff on headphone listening is at
http://www.linkwitzlab.com/reference_earphones.htm

 Ah Head-fi cencors yes folks this is a real name Lip****z


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## Prune

This is slightly off topic, but today's blog entry at the TCJ is worth checking out.
http://www.tubecad.com/2004/blog0012.htm


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## ppl

yes that was indeed funny and brought up a good point that taking any extreme is not good. but a few of my favorite remarks from that artical is 

 "The perfect is the enemy of the actually built and the perfectly expensive"

 "Audio suffers from two types of puritan: those who follow the "absolute" sound and those who follow the distortion meter."

 "High-quality ingredients are not enough. Understanding and art are needed"


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## Syzygies

An interesting reconciliation game here would be to have a design contest for the simplest DIY circuit that lit up a green LED when you plugged in a Burr Brown OPA-627, and a red LED when you plugged in an Analog Device AD-8610. People would of course divide on whether such a circuit is even possible in theory, how accurately anyone could separate into bins a few dozen such chips by listening, and so forth. I'm of the opinion that if you staked enough money on this, there'd be a few dozen different working "discriminator" circuits submitted as entries. I'd love to see how they worked. Someone could then turn this around into a better amp design.

 This reminds me of the advent of computer shuffling in duplicate bridge tournaments: Rather than shuffling one deck by hand, writing out the deal, and making copies of the deal for the remaining tables, tournaments started printing out the deal by computer, and making copies for all the tables. Very sensitive bridge players noticed differences in the play of the hands. The computer experts rolled their eyes at this; the computer algorithms for shuffling were drop dead simple and had to work. What was really going on? I proved a theorem with Persi Diaconis on how hand shuffling worked, leading to the recommendation that people should shuffle seven times to achieve a reasonable approximation of randomness. People weren't shuffling enough; the bridge players who noticed something were right.

 Here, I have complete faith in the conflict discussed in this thread. I have faith that the subjectivists who notice something are right, and I have faith that the objectivists can come up with better measures that capture what the subjectivists are hearing. Knowing just enough about differential equations to be a danger to myself and others, I read the PSpice links in horror. The objective measurements for audio amps are like sticking a thermometer somewhere in the ocean. Nothing wrong with the theory, but it only goes so far.


----------



## Sovkiller

Quote:


  Originally Posted by *Syzygies* 
_I have faith that the subjectivists who notice something are right, and I have faith that the objectivists can come up with better measures that capture what the subjectivists are hearing._

 

The only problem is that according to some "audiophiles", the differences in audio quality are there, EVEN, when they are not mesurable by any instrument to the date, nor by anybody, that leads to a couple of conclusions, or they are not hearing absolutelly nothing and all is in their heads due to placebo effect, or what is being measured to the date, is not what really shows that difference.....I'm personally and nothing wrong on that, inclined to believe the first one, as I know that placebo effect exists, and is real, and I have seen (and read) of many cases of well known and good "audiphiles" fail miserably in a really double blind test....


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## Prune

Look, the most appropriate measurement is, and it should be obvious, that of the human ear, and this is a point many audio objectivists miss. Measuring by electronic equipment is merely for practical convenience, but listening tests are a must for truly meaningful and comprehensive results. In the sciences where humans are part of the system, from drug testing to psychology experiments, testing on subjects is a given. Specifically regarding perception, companies and researchers working on new video and audio codecs know that the final test that must be passed is that of perception rather than some measured statistic.

 On the other hand, this does not really support the subjectivist positions since these perception-based tests must be conducted rigorously to be valid, and they are thus inevitably blind tests (better yet, double blind tests). The frequent objection from the subjectivist camp that a negative in a test doesn't prove lack of difference is correct; however, a series of negatives probabilistically implies that. Of course, the assumption here is that such tests are conducted properly, _which generally has *not* been the case_ in audio equipment testing. For some good discussion of methodologies that try to satisfy both camps see Jon Risch's comments on the AudioAsylum forums.


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## Garbz

One obvious thing has been missed. If the placebo effect really exists why spoil it. If someone swares by the use of a certain power cable that makes drastic improvments to how his system sounds, then why spoil it for him.

 Does my Gilmore amp sound better because I spent months building it? Possibly and subjectivly it would. Why ruin it with a double blind test.

 The real point in audio is how people enjoy it. I don't care much about mathematics as long as it sounds good to me. Let me keep my placebo. Just don't tell me that in a double blind test it's identical.

 /NOTE: Author of above posts does not believe power cables make a difference


----------



## Prune

Yes and no. This has been discussed at length at the diyaudio forums by people like Steve Eddy and myself. The problem is that many people, if they knew it was only placebo, wouldn't spend the money on it. Therefore subjectivist reviews, by not acknowledging the placebo effect, do a great disservice in spreading their misinformation, making consumers believe there is a difference not accounted by placebo. There is a word for making money based on false claims: scam.


----------



## Prune

This directly contradicts Lipsh!tz:
 Harwood, H. "Audibility of phase effects in loudspeakers." Wireless World, January 1976, pp.30-32.
 User wimms at diyaudio also criticizes Lipsh!tz:
http://www.diyaudio.com/forums/showt...853#post518853

 However, the following shows that some localization cues are monaural:
 "Temporal Localization Cues and Their Role in Auditory Perception." 95th AES Conference, Preprint #3798
 Although phase cues between ears are used for localization, some have argued that phase distortion identical to both channels is not perceptible. However, the above article doesn't say monaural localization cues are only amplitude dependent, so I it leaves the possibility that monaural phase cues matter for localization.


----------



## Prune

This is a bit off topic but I didn't want to start a new thread. We've discussed binaural recordings here, and the crosstalk-cancellation needed to play them properly over speakers.
 There are a number of commercial DSP units that do that to various success, but are generally very expensive. The only software that I've found is this, and it's not free:
http://www.wavearts.com/WaveSurroundPro.html
 The method is described in Gardner's thesis, along with making binaural signals from non-binaural ones.
http://sound.media.mit.edu/Papers/gardner_thesis.pdf
 Detailed HRTF measurements are available freely, so I don't know why I can't find any free software that will do this. It would be great to find a tool that would convolve a music file with the appropriate filters, so I could rip, process, and burn all my CDs for a better speaker listening experience.
 Of course, I could just put a physical barrier between the speakers, but people would laugh when they see it.


----------



## KZEE

Quote:


  Originally Posted by *Prune* 
_Well duh, that's by definition. That's why religion is bull****, because it's unfalsifiable._

 

You're approaching religion from the wrong angle... you're getting caught up in the doctrines of religion, and missing out on what I believe to be true religion, which is a relationship with God. If you were to ask God to reveal Himself to you, and then spend a week or so keeping that question before Him and giving Him a chance to show Himself to you, I'm convinced that at the end of that week you'd have a different opinion of what true religion is.


----------



## KarlDL

Tonight I breadboarded my first "serious" headphone amp, measured it & did some listening. OK, but not spectacular on the subjective, into the limits of the measuring instruments on the objective. My full-sized system beats this initial amp w/Senn 600s readily. Obviously, there is much more to do on the amp, but I knew that before power-up. (Hmmm - is that why I'm not dazzled?)

 Much of what we hear can be measured, with the right techniques, of which 1930s THD is just one of an arsenal of methods needed (some of which haven't been discovered yet). Years ago, I found that perception of distortion is much more sensitive to IMD than THD. Ordinary amplitude clipping produces much more IM than HD in complex-waveform simulations. Yet so many measurement-oriented folks remain fixated on THD (this is less so in Europe). And the vast majority of published data involves THD or 2-tone IMD, nothing more complex.

 This gets more interesting when feedback is considered. When I listened to a bandwidth-limited, measureable delay, low-distortion amp with and without FB, the FB worsened the sound. The FB was obviously trying to correct a condition that had already passed and, therefore, adding a stale corrective factor into a later input signal. Does this mean that FB is always bad? Or that this particular set of propagation delays and bandwidth limitations just wasn't compatible with the particular FB used?

 Phase distortion and phase modulation in particular aren't considered in traditional audio measurements, yet we know they're audible.

 The popular steady-state tests reveal few of these phenomena, as feedback aligns itself to correct the signal within the time frame of the measurement process. Could other, transient-oriented tests reveal them? Maybe not all phenomena, but certainly more than what we obtain from the traditional methods.

 So, where are the techniques, and why haven't they been developed? First, they don't illustrate theoretical principles being taught at the undergraduate level, so there's little market in the university laboratory environment for test equipment & techniques that don't compliment the traditional educational sequence. Second, some of the folks with the best potential ability to develop correlational techniques simply reject objective measurements out-of-hand. If half the effort expended in arguing the merits of subjective vs. objective went into the development of better-correlated measurement techniques, objective measurement and subjective result would both take a leap forward, I would think. 

 We have computational and simulation tools available now that were unimaginable when I was an undergraduate 30 years ago. Hopefully, some bright young minds will step outside the box and develop DSP applications that reveal more of the anomalies we hear, thereby providing the means for more rapid sonic improvement of products.

 Appropriate measurements help us understand what we hear. Improving measured results is a tool that's often helpful along the road to better sound. But the goal cannot be solely the measured data, as that's not what satisfies the customer in the end. That doesn't invalidate the usefulness of measurement, it merely establishes some limits on it.

 The measurement techniques I have available on my bench won't, by themselves, help me improve my amp's initial sound. Steady-state tests won't reveal a dynamic regulation issue in a power supply, for example. But they'll come in handy every now and then during the evolution of this project, which I will know is complete when it matches or beats the sound of my full-sized system.


----------



## Francis_Vaughan

Quote:


 When I listened to a bandwidth-limited, measureable delay, low-distortion amp with and without FB, the FB worsened the sound. The FB was obviously trying to correct a condition that had already passed and, therefore, adding a stale corrective factor into a later input signal. 
 

Right, first up I guess I should say "Hello" to all. First post here and all that. Getting close to a lot of areas I am very interested in.

 So, to weigh in:

 I'm curious how you did this evaluation. Listening to a given amp in both open loop and closed loop is not going to be at all easy. What was the open loop gain? One assumes it must have been reasonably low, or you could not have done the test. So what was the feedback ratio? At what frequency is this? 

 Secondly, the idea that the amp was "trying to add a stale factor" really won't fly. I have no doubt that they sounded different, and your preference, but the rationale for the difference is very hard to believe. This goes to the root of how a feedback amplifier works. Yes there is a delay, and yes it is important. Indeed it is pretty much covered in the Nyquist stability criterion. 

 There could be a huge number of reasons why an amplifier could sound worse when the feedback loop was closed. If it had been designed to work open loop I would have grave misgivings that it would also operate correctly with the loop closed. It might operate OK, and indeed generally seem to be working, but immune to some of the well known failures of feedback design, that is harder to judge.


----------



## shimage

Quote:


  Originally Posted by *Prune* 
_I have never heard anyone define philosophy the way you did. It is not the job of the philosopher to postulate scientific theories, it is the job of the scientists to both do that and test them -- thus the distinction between theoretical and experimental scientists in some theories (especially physics). Physics theories are generally born in the minds of theoretical physicists, not philosophers. In regards to science, philosophy concerns itself with metaphysics, ontologies, etc., defining what science is, how its methods can be rationally justified, and just what scientific results actually mean. Doing the science is left to the scientists._

 

That's pretty recent. It's only been the case from the start of the 20th century. Keep in mind that Enrico Fermi was a great theoretician _and_ experimentalist. The big reason for the dichotomy nowadays seems to be that the mathematical sophistication required for most "research grade" theoretical physics precludes one from being at the forefront in both "fields". As far as I know, one of the prerequisites for being a good experimentalist is understanding the underlying theory. And I mean they have to really understand it well enough to know exactly what they're doing, and not hackishly applying equations for no apparent reason, I mean, that's what engineers are for, right 
	

	
	
		
		

		
			





 * You'll note that such a dichotomy _does not exist_ in the other sciences (I'm not counting "theoretical" chemists here, since they're basically molecular physicists in the Chemistry building).

 Addressing the Philosophy issue, I've heard from some fellows (odd ones, but respected nonetheless) that philosophy will have increasing importance in Physics as we move along into this new century (which, unfortunately for me, looks to be the century of Biology). Here at the University of Washington, we've got a Professor of Philosophy that's adjunct in Physics. He's even got several PRLs under his belt, so one assumes that he knows his stuff. I'm not going to defend it any further than to say that philosophy did, at one point in time, have a place in Physics. To say that it never will again, is ... well, bold, I think. Don't get me wrong, I like to mock philosophers as much as the next guy (one recalls the Sokal hoax with fond memories), but I think that to seriously write them off wholesale is a bit much. 

 As for the topic of the thread, I believe very strongly in blind tests. I have such _faith_ in them that I further believe they represent the only *true* data (though perhaps it's going a bit far...). Sure, they have to be conducted right, but to discard them as useful tools simply because they _usually_ aren't conducted right is foolhardy. A dearth of good data is merely evidence that someone needs to take good data. The fact that the people with the most interest in this field, with the greatest resources for accomplishing these tasks have not even attempted them implies to me that the effects in question must not exist. It is simply a matter of money and desire, and don't tell me that magazines like _Stereophile_ lack the funds. As for desire, I would expect anyone with a finite budget to find this information at the heart of the matter.

 Now ... as for Mr. Atkinson
  Quote:


  Originally Posted by *John Atkinson* 
_[...]This collection a) proves that, of all scientists, theoretical physicists seem to have their feet most firmly on the bedrock of reality,[...]_

 

I hate you. To pick arguably the most beloved of all physicists and apply him as a general model for all theoretical physicists (and modern ones at that!) is utter blasphemy. There is a very severe gap between the theorists of yore and those we are stuck with today (though the size of this gap, strongly depends on the particular subfield...). I have heard that Russian string theorists call themselves mathematicians and eshew the title "physicist" because they don't think that what they're doing is, strictly speaking, physics yet. Let us not forgot that the final arbiter of what is real and what is fantasy is the experimental result. Even Einstein knew this.

 * For those that do not see that I am joking here, I am applying the standard engineer stereotype, as seen by physicists. I mean no harm, just thought I'd throw it in for kicks.


----------



## Nixie

Well, it's not really a dichotomy because there are in-betweens. This is just division of labor, of course. Since Newton's time, the sciences have become too much for one person to know fully in detail, thus the increasing number of specializations. It's been a while since I posted that, but I think my point was that whatever was originally the case, _natural philosophy_ is no longer a branch of philosophy (and that's why we don't call it that anymore, instead referring to it as _science_). I see an enormous separation between philosophy and science today.


----------



## Crowbar

Here's a great addition:
 "Multitone Testing of Sound System Components - Some Results and Conclusions" in the November 2001 AES journal.


----------



## prescient

This might seem like a ridiculous suggestion, but is there really any reason you couldn't just make two cheap amps (cmoy equivalent), mark them internally, power them w/ the same power supply, use two different chips and weld em shut? Just ship them around to the head-fi members and gather data. When you are done testing just cut the amps open and see which one got picked more often or if it was 50/50.


----------



## Crowbar

It's not that simple (as you have guessed). Proper blind testing is a wide subject in the field of psychology and experimental science, and audio presents its own complications. But this has already been discussed to death at the AudioAsylum and DIYaudio forums. What's the most potentially constructive area to research is finding measurements and metrics that correlate best with perception, so that the complexity and carefully controlled environments of blind testing can be avoided. The various papers quoted in this thread show that over the past decade this has begun picking up steam, but lots more is needed.


----------



## ezkcdude

Quote:


  Originally Posted by *Crowbar* 
_It's not that simple (as you have guessed). What's the most potentially constructive area to research is finding measurements and metrics that correlate best with perception, so that the complexity and carefully controlled environments of blind testing can be avoided._

 

Those tests won't tell you why individuals have different preferences, if not perceptions.


----------



## Crowbar

Quote:


  Originally Posted by *ezkcdude* 
_Those tests won't tell you why individuals have different preferences, if not perceptions._

 

While there are variations in the auditory system, generalizations across the population can be made, just the same as is the case for the visual system. Indeed, much of the early neural processing of sound exciting the auditory cilia has already been simulated by simple analog circuits.

 Preferences are irrelevant; only preceptability of differences matters, and this is why ABC/hidden reference is a standard in the world of blind testing. Any euphonic distortion that one likes should be added explicitly by DSP or analog filters, not coincidentally by the source, amplifier, or headphone/speakers, whose job is to produce an amplified sound indistinguishable from what reached the recording microphone (mastering of recordings notwithstanding).

 So, now we're interacting in threads on here, diyhifi, and diyaudio. What next, you'll post at prodigypro? ;P


----------



## prescient

I didn't notice this article in the thread. It was fairly interesting.


----------



## Crowbar

Quote:


  Originally Posted by *prescient* /img/forum/go_quote.gif 
_I didn't notice this article in the thread. It was fairly interesting._

 

Wow, someone didn't know how to use OCR when scanning, and the whole PDF text is as an image, making for a huge download...

 Another interesting thing is that phase intermodulation seems to be audible in far smaller amounts than THD. That could explain why amps such as the Pass Labs ones sound so good even though their THD can be as much as 0.1%.


----------



## ezkcdude

It's been a while since this thread was active, but I thought I'd attach a link to an interesting blog by Peter Aczel (aka The Audio Critic). He discusses some new software (Audio DiffMaker, sort of like the Unix Diff command, but for audio components), which could potentially make subjective listening tests easier to perform and detect differences b/w components.

http://theaudiocritic.com/blog/index...Id=35&blogId=1


----------



## Crowbar

_Inaudible High-Frequency Sounds Affect Brain Activity: Hypersonic Effect_. The Journal of Neurophysiology, Vol.83 No.6, June 2000, pp. 3548-3558.
http://jn.physiology.org/cgi/reprint/83/6/3548.pdf


----------



## regal

As an engineer I was always in the measurement crowd, until I saw that blind kid on a talk show who could "see" by making clicking noises like a bat. If he can tell the difference between a banana and an orange by listening to his voice echo of them, I sure people can tell the difference between opamps.
 If that kid doesn't exemplify that modern science is a long way from understaning psychoacoustics I don't know what would.

 Then I built a tube amp and now know that not all watts are the same.


----------



## ezkcdude

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_If he can tell the difference between a banana and an orange by listening to his voice echo of them,_

 

Are you sure he didn't just smell the difference? If you put a banana and orange in front of my face, I could tell the difference blindfolded without making bat like sounds 
	

	
	
		
		

		
			





 .


----------



## regal

He was doing other things too, like the difference between a phone and a TV. It was amazing, is amazing what the brain can do.


----------



## Crowbar

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_He was doing other things too, like the difference between a phone and a TV. It was amazing, is amazing what the brain can do._

 

It is amazing the self-congratulatory patting on their backs humans do in calling themselves amazing. I guess unabashed pride has no limits.

 As someone who has studied cognitive psychology and neuroscience, I see the brain as something, like all the products of evolution, that is far from optimized and in fact a barely 'will make do in most circumstances' solution. Any familiarity with the suboptimal heuristic algorithms the brain uses for most cognitive processing, and not to mention the extreme inefficiency from an energy point of view (it consumes an inordinate fraction of your calories), and I won't even get into all the mental problems and diseases that are far from uncommon...

 Humans like to see themselves as the peak of evolution. In fact nothing could be further from the truth. By any evolutionarily meaningful measure of success, be it total numbers, total biomass, adaptability, resilience, being widespread throughout the biosphere in all different environments, it is bacteria that win outright, with no multicellular organism coming close. Why did they win? Simple (pun intended): they're just complex enough, and no more. Chances of a mutation being detrimental are much lower because there is less complexity that could be ****ed up, and the short life cycle and horizontal gene sharing makes them readjust to pretty much any change in environment in no time.


----------



## regal

Quote:


  Originally Posted by *Crowbar* /img/forum/go_quote.gif 
_It is amazing the self-congratulatory patting on their backs humans do in calling themselves amazing. I guess unabashed pride has no limits.

 As someone who has studied cognitive psychology and neuroscience, I see the brain as something, like all the products of evolution, that is far from optimized and in fact a barely 'will make do in most circumstances' solution. ._

 



 I guess you're an expert in Humanity, what you do read a couple books? Give this poster the Nobel prize, he thinks we're inferior to bacteria, brilliant.

 Consciousness, yes the brain is the final frontier of modern science and philosophy.


----------



## Crowbar

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_I guess you're an expert in Humanity, what you do read a couple books?_

 

This is known as the _ad hominem_ fallacy: attacking the one presenting the message instead of addressing the actual argument I presented. It's a sign that you're unable to logically refute what I wrote (either because you've stubbornly taken an indefensible stance on the issue and your ego is not allowing you to admit defeat, or, that as well as an intellectual weakness preventing you from coming up with a plausible counterargument), so you have to resort to attacking my credentials--a clear sign you have lost the argument. You claimed to be an engineer, and I'm disappointed you would resort to hand-waiving, fallacious reasoning.

  Quote:


 Give this poster the Nobel prize, he thinks we're inferior to bacteria, brilliant. 
 

I have presented a view that most biologists would agree with, and again, you have failed to give any counter-argument.

  Quote:


 Consciousness, yes the brain is the final frontier of modern science and philosophy. 
 

That's total BS. I have studied cognitive psychology and neuroscience in university, and I can tell you that we are well on the way of elucidating the neural correlates of consciousness. The specific regions involved in making consciousness, and the general mechanisms have already been pretty well nailed down by the research of A. Damasio et al.

 Since I initially joined this forum in 2003, I've seen a significant increase in the low quality posts typified by these examples by regal. I wonder if this happens to all forums--as popularity increases, the SNR drops since many of the latecomers are just people jumping on the bandwagon rather than joining not due to peer influences. The discussion I was involved in on the first page of this thread was largely free from the spurious noise people like regal are injecting into recent pages.


----------



## regal

A. Damasio is not a determinist ! Hell he even wrote a book discrediting the father of cartesian thinking.

 You say consciousness has been "nailed down" like some algebra formula describing gravity.

 You say a brain is something which "barely makes do", anyone with any knowledge of brain physiology knows that the brain is the most complex steady state "chemical reaction" in existence. All I'm saying is my brain's perception of sound is "better" than a microphone (~100 part count) or an oscilloscope (~1000 part count.) How many brain cells do we have? Much more complex "instrument" than a mic or a scope. 

 Your post about bacteria just rubbed me the wrong way, I apologize but Humans have been to the moon. Humans distill mold to selectively destroy bacteria. Humans can engineer the genetic makup of bacteria to spit out insulin for Christ sake.


----------



## cosmopragma

Never mind


----------



## Crowbar

Cartesianism is not equal to determinism, so your first sentence is a _non sequitur_.

 The brain is a physical object. It behaves according to the laws of physics. Quantum physics is not deterministic, so the brain is not either, but that non-determinism is in the form of randomness and so indistinguishable from a deterministic system with really good pseudo-random number generators. Physical limitations such as the forced quantization of information in the real universe resulting from the Bekenstein bound mean that the brain is equivalent to a discrete computational device (i.e. it can be simulated on a powerful enough computer), and not super-Turing (Penrose was wrong, and his arguments to the contrary have been exhaustively refuted). We are just working out details, but the needed raw computational power is less than a couple of decades away.

 The brain is not highly optimized by evolution for the exact reason of its complexity. Evolution is an optimization algorithm and something as complex as the brain could have only been partially optimized in the relatively short time its been around. Only the simplest processes in living organisms, interacellular chemical processes, are highly optimized (and a few are completely optimal, in the sense that no other setup of the process can be more effective in whatever the particular function), since short life cycles and length of existence of single-celled organisms has allowed exploration of essentially all possible configurations. Not so for anything multicellular.

 Humans have been to the moon and use bacteria, but when humanity no longer exists bacteria will still be around. We are extremely fragile and not very good at inhospitable environments or very drastic environmental changes. We are also completely reliant, as is the rest of the biosphere, on bacteria to complete the nitrogen cycle, and algae for the majority of the photosynthetic oxygen recovery. Considering how poorly we are doing in attempts to control the environment, and how little attention space gets (and is likely to get in the future, with the exception of weaponization issues), it's extremely, unrealistically optimistic to think humanity will survive another thousand years, whereas the bacteria will remain until the sun runs out of fusion fuel.


----------



## peelax

Quote:


 Evolution is an optimization algorithm and something as complex as the brain could have only been partially optimized in the relatively short time its been around. 
 

If it had been optimised to a global optima would that mean we wouldn't bother arguing about whether bacteria are better than humans on an internet headphone forum? 
	

	
	
		
		

		
		
	


	




  Quote:


 Only the simplest processes in living organisms, interacellular chemical processes, are highly optimized 
 

I'm sorry but just because bacteria are optimised for eating poo does not mean that they are better than us. Would you say that something like a hinge is better than us because it is perfectly optimised for its job?

  Quote:


 We are extremely fragile and not very good at inhospitable environments or very drastic environmental changes. We are also completely reliant, as is the rest of the biosphere, on bacteria to complete the nitrogen cycle, and algae for the majority of the photosynthetic oxygen recovery. Considering how poorly we are doing in attempts to control the environment, and how little attention space gets (and is likely to get in the future, with the exception of weaponization issues), it's extremely, unrealistically optimistic to think humanity will survive another thousand years, whereas the bacteria will remain until the sun runs out of fusion fuel. 
 

I do agree with most of this, I do believe that scientific advances will mean we will survive in the long term or at least our mechanical descendants


----------



## Crowbar

There's no actual gobal optimum, as environment changes, and adaptability to those changes would tend to be higher when you're not in a global optimum for the particular situation, but diversified in some way so that as the fitness function landscape changes, at least some of the population would be above the threshold for death. It is simply impossible for multicellular organisms to be able to change as fast as bacteria, partly due to far longer life cycle, partly due to lack of horizontal gene exchange, and mostly due to the fact that a larger portion of possible mutations are detrimental or even fatal.

  Quote:


  Originally Posted by *peelax* /img/forum/go_quote.gif 
_just because bacteria are optimised for eating poo_

 

They're optimized to survive. And from an evolutionary perspective, which is what I'm discussing as was clear with my initial post, that is all that matters.

 Ultimately, of course, even they would disappear. Even if space-faring bacteria riding on chunks of rock struck off the planet by an asteroid impact are able to escape Sol's death, accelerating expansion guarantees that life (whether biological, mechanical, pure energy, whatever) will eventually become impossible in the universe. The expansion guarantees that non-gravitationally bound galaxy clusters will in the end spread apart from each other faster than the speed of light (possible since the space itself is expanding and the limit applies only to matter/energy traveling through space) . Thus, a finite amount of matter/energy will remain in any given Hubble volume, and though globally the expansion prevents entropy from equalizing things everywhere, locally in any Hubble volume there will be no energy gradients left with which to do work (such as living, or anything else). Beyond that, on extremely long time scales baryon decay and in even larger ones a quantum smearing of positions (I'm using the term in the same sense as H. Stapp) essentially blurs out any kind of structure.

 Back to optimization: what happens when you have an evolutionary algorithm and you keep diversification (mutation etc.) but remove selection? If the population is elevated towards some (local) minimum, then over time its average fitness will decrease as it randomly diffuses (less paths lead towards higher fitness unless you're closer to a minimum). Humanity is in that situation. The majority of selection pressures have been removed. Clearly, natural selection cannot be practically applied to humans, but artificial selection can, and should, be used.


----------



## regal

Quote:


  Originally Posted by *Crowbar* /img/forum/go_quote.gif 
_. Clearly, natural selection cannot be practically applied to humans, but artificial selection can, and should, be used._

 


 I really hope readers of this thread understand what Crowbar is talking about. Artificial Selection (Eugenetics) was a main impedus of the Third Reich. 

 A headphone forum is no place for pushing genocide or sterilization of "the inferior."

 Mods please close this thread. It is turning into a pulpit for political extremists.


----------



## Crowbar

You're way over the line, since I'm not proposing anything that can be likened to what the Nazis were doing, which was just a cover for genocide. And again you are appealing to emotion instead of addressing anything logically. You have shown yourself to be nothing but a troll.

 What I'm talking about is already being done in artificial insemination procedures, where the parents often have the option to genetically screen which fertilized eggs are implanted. What I was going towards is that such arbitrary intervention is not necessarily useful for humanity as a whole, since parents are likely to choose for the same attributes (no disease X, strong body, smart mind), and thus in the long run diversity will disappear.

 Modern genetic intervention is advocated by plenty of scientists nowaday, and has nothing to do with restricting people's ability to freely reproduce (though China is doing this as population control); moreover, what Nazi Germany did was not scientifically based in any way, and gave a bad name of something that nowadays is supported by *mainstream biologists*, such as *Nobel laureate* John Sulston, considered the UK's leading geneticist, who said "I don't think one ought to bring a clearly disabled child into the world", etc.

 James Watson is one of the *co-discoverers of the structure of DNA*, and also a *Nobel laureate*. Here's what he has to say in full support of a what is essentially modern eugenics (BTW notice the correct spelling, you couldn't even get that right): http://www-tech.mit.edu/V119/N46/46watson.46n.html

 As a third famous name to add to the list, everyone's favorite geneticist Richard Dawkins is also a supporter of some forms of genetic intervention.

 It's also interesting to look at Wikipedia's article on the subject, and especially the secion entitled "Ethical re-assessment".

 I do want to thank you, regal, for meeting my expectation and being the first to meet Godwin's Law on this thread, which states that As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one.

 Why should this thread be closed? I've been contributing since page one, and you're the last one to be telling moderators what they should do, especially after your obvious trolling and a lack of ability to present a rational argument that goes far beyond that of the most extreme subjectivist audiophile. I've backed up my stance with explanation and reference to the highest authorities in modern genetics. Now let's see if you can come up with something more than name-calling.


----------



## mcshaggy2

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_I really hope readers of this thread understand what Crowbar is talking about. Artificial Selection (Eugenetics) was a main impedus of the Third Reich. 

 A headphone forum is no place for pushing genocide or sterilization of "the inferior."

 Mods please close this thread. It is turning into a pulpit for political extremists._

 

i read: 

  Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_I can't defend myself with real information so I'm going to make a ridiculously baseless comparison between you and Hitler. 

 Could you do me a favor and close the thread before I make myself look any more like an idiot? You could blame it on his Nazi agenda._

 


 seriously, do you have anything to actually argue with in here regal?


----------



## Crowbar

Quote:


  Originally Posted by *mcshaggy2* /img/forum/go_quote.gif 
_Misc: various Starquad cables_

 

Those have high capacitance (comparable to coax) and are not really suitable for line level applications unless you have low output impedance on the source. But if the cable is short and you have noise problems, works good.


----------



## Febs

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_I really hope readers of this thread understand what Crowbar is talking about. Artificial Selection (Eugenetics) was a main impedus of the Third Reich._

 

Time to invoke Godwin's Law. You lose.


----------



## Crowbar

Quote:


  Originally Posted by *Febs* /img/forum/go_quote.gif 
_Time to invoke Godwin's Law. You lose._

 

Already done...
  Quote:


  Originally Posted by *Crowbar* /img/forum/go_quote.gif 
_I do want to thank you, regal, for meeting my expectation and being the first to meet *Godwin's Law* on this thread, which states that As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one._


----------



## peelax

Quote:


 natural selection cannot be practically applied to humans, but artificial selection can, and should, be used 
 

That is rather a vague and offensive statement Crowbar.

 Scientific advance should be used to give all people as good a life as possible. Only the person involved can make the decision about whether they should live or not, and hopefully they will be given the opportunity to have a good a life as possible and so will want to live. I don't think these biologist’s views bare much weight Crowbar. I don't think we have anything like the depth of understanding that would be required to make the decisions involved in "artificial selection".

  Quote:


 They're optimized to survive. And from an evolutionary perspective, which is what I'm discussing as was clear with my initial post, that is all that matters. 
 

 Quote:


 
 

We are a bit of an evolutionary wonder. It seems strange that you argue that at the same time that we are not at the peak of evolution and that evolutionary pressure no longer effects us, may be we have "out grown" it to some extent, but then what does that tell you? The old fitness function is not comprehensive enough anymore - survival. So arguing in those terms is a bit pointless unless you are talking about simpler organisms.


----------



## Crowbar

Quote:


  Originally Posted by *peelax* /img/forum/go_quote.gif 
_That is rather a vague and offensive statement Crowbar._

 

I'm just echoing many biologists, such as the Nobel winners I referenced. There are more specifics in their writings, such as the one I linked to, and others that a websearch will find for you. It is offensive for you to question the ethics of these scientists.

  Quote:


 Only the person involved can make the decision about whether they should live or not, and hopefully they will be given the opportunity to have a good a life as possible and so will want to live. 
 

Huh? I'm not advocating killing anyone, the way natural selection works. You better do some research. I'm talking about something that's already being done individually by parents seeking fertility treatment, genetic screening of which fertilized eggs are allowed to grow. That was clear in my post.

  Quote:


 I don't think we have anything like the depth of understanding that would be required to make the decisions involved in "artificial selection". 
 

Indeed, and it needs attention, because the version being done by individuals right now is becoming more commonplace and can actually be harmful to the population gene pool since only parents' wishes for characteristics are being selected for.

  Quote:


 We are a bit of an evolutionary wonder. 
 

There we go again. You need to back that up. The chemical machinery of a single cell is at least as complex as the neural organization of the brain, and indeed, most of your genes deal with specifically that small scale complexity. You share half of your genes with a banana. Thus, even a bacteria already contains in it complexity that is of the same order of magnitude as a human. More goes on in getting one of your cells to work, than when a cell is given, to put you from a bunch of them. That is why it took a couple billion years for the simplest life to show, whereas multicellular life is a much more recent development. You will find that what I'm saying here is mainstream scientific thinking if you do some websearching on the fact that the 'evolutionary ladder' with huans at the top was never considered an scientific idea. One site puts it succinctly:

 [size=xx-small]It is extremely important to realize that evolution is change without direction. Evolution is opportunistic and it is not caused by the “urge of individual organisms toward something better, nor is it the series of the trends from the simple to the complex” (G. Ledyard Stebbings). For this reason, the term “evolutionary ladder” is false as it symbolizes evolution as moving somewhere, as being a progression towards the summit of perfection. The most accurate analogy to evolution is that of a branching bush, where each twig grows randomly and in different directions. Contrary to popular belief, humans are not on top of the evolutionary ladder. We are simply another branch on the bush of life.[/size]

 Or another excerpt from a Dawkins review of one of Stephen J. Gould's books:

 [size=xx-small]Gould drives his point home with an admirable section on bacteria. For most of history, he reminds us, our ancestors have been bacteria. Most organisms still are bacteria, and a serviceable case can be made that most contemporary biomass is bacterial. We eucaryotes, we large animals, we brainy animals, are a recent wart on the face of a biosphere which is still fundamentally, and predominantly, procaryotic. To the extent that average size / complexity / cell number / brain size has increased since the ‘age of bacteria’, this could be simply because the wall of possibilities constrains the drunkard from moving in any other direction. John Maynard Smith recognized this possibility but doubted it when he considered the matter in 1970:

 The obvious and uninteresting explanation of the evolution of increasing complexity is that the first organisms were necessarily simple . . . And if the first organisms were simple, evolutionary change could only be in the direction of complexity.

 [/size]

  Quote:


 It seems strange that you argue that at the same time that we are not at the peak of evolution and that evolutionary pressure no longer effects us, may be we have "out grown" it to some extent, but then what does that tell you? The old fitness function is not comprehensive enough anymore - survival. So arguing in those terms is a bit pointless unless you are talking about simpler organisms. 
 

There's no contradiction here. Your confusion stems from the fact that you fail to differentiate the two effects of having a good gene pool: it's not just about surviving, and we've bypassed this in a lot of ways so that now many individuals that would not have survived without civilization can, but at the same time quality of life remains compromised. Of course, modern medicine can improve that, but if you have a continually worsening gene pool as I've provided an argument in an above post will happen, then this will become a much bigger problem in the long term. Genetic screening of zygotes can prevent lots of suffering in the future. It's already being done by individuals for their own selfish reasons, and what I'm after is that it should be regulated and controlled by international scientific organizations with the total human gene pool in mind.


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## rsaavedra

Quote:


  Originally Posted by *Crowbar* /img/forum/go_quote.gif 
_Thus, even a bacteria already contains in it complexity that is of the same order of magnitude as a human._

 

Hmm... are you sure of that? You seem to set an amoeba at the same level of complexity of a human stem cell, or a fertilized human egg. Are you sure someone has compared those complexity levels appropriately? Or rather, are you sure that _you_ are comparing them appropriately? Such comparison might trascend biology, might involve complexity theory and math.

 A fertilized human egg, regardless of how many genes shares with an amoeba, has other extremely complex internal encodings in its DNA to allow for the appearance of very different types of cells, which can eventually form organized and highly differentiated, yet cooperating tissues, so that they work together allowing the existence of a very complex multicellular organism. These internal encodings allowing the proper morphology of that organism (from just one cell!) involve such complex things as multiplication of specific cell types _up to a specific population size_, precise orientation/placement of such cell types with respect to some other surrounding cell types, and might involve even programmed self-destruction of specific cells at specific points in time during the early development stages of that organism. All of this extra "programming complexity" guiding the coordination and progressive arrangement and workings of millions of cells of different types (all in just one cell at the beginning, or we should really say just two: fertilized egg + fertilizing spermatozoid) is clearly beyond what the typical unicellular organism has genetic information for. In what magnitude it is "beyond", well that I'm not sure, but that's part of my point.

 Percentage of genes shared is not the same as the operational complexity of different genetic machineries. I don't think it is that easy to compare the complexity levels of the way different genetic codes work, despite the fact that they are based on the same molecules and might share large %s of genes. Moreover, in multicellular organisms there are extra complexities associated to ongoing interactions and interregulations between tissues; extra operational complexities that pile up on top of the extra genetic and morphological level complexities.

 Now, there's also the point that operational complexity of a genetic code may not necessarily be the best measure of evolutionary advancement. Depends on how biologists choose to define evolutionary advancement or "success".


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## Crowbar

Hi, thanks for actually using rational arguments, unlike regal.

  Quote:


  Originally Posted by *rsaavedra* /img/forum/go_quote.gif 
_Percentage of genes shared is not the same as the operational complexity of different genetic machineries._

 

This is correct; indeed, there is quite a lot of junk DNA (though whether some of it may in fact play a part; it's controversial). Nonetheless, it's useful for the _order of magnitude_ comparison I was making.

  Quote:


 Moreover, in multicellular organisms there are extra complexities associated to ongoing interactions and interregulations between cells and tissues 
 

Sorry, but from a systems perspective, these processes simply replace the domain of the environment of the single-celled organism. The single-celled being has to deal with an environment of air/water/soil/whatever, whereas the cell of a multi-cellular organism deals with an environment of others of its kind (which obviously is just a refinement of the colony environments that some of the single-celled organisms form).

  Quote:


 Now, there's also the point that operational complexity of a genetic code may not necessarily be the best measure of evolutionary advancement. 
 

It's not a measure of it at all. I've already provided a number of citations for actual evolutionary success measures, such as percentage of total biomass and adaptability.

  Quote:


 Depends on how biologists choose to define evolutionary advancement or "success". 
 

The definitions I've referenced are not arbitrary, since they are a direct consequence of what evolution actually is, an optimization algorithm directed by varying environment.


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## rsaavedra

Quote:


  Originally Posted by *Crowbar* /img/forum/go_quote.gif 
_Sorry, but from a systems perspective, these processes simply replace the domain of the environment of the single-celled organism._

 

Still, the genetic code in a multicelled organism is programmed for the development of a very specialized and highly complex morphological process, an extra complexity that is not present/encoded in the unicellular organism, even though the latter might form colonies. Such processes are extra complexity levels that were encoded in the one original cell of the multicellular organism. Extra complexity vs. less complexity. So my point stands: even though it is not trivial at all to compare the levels of complexity between a unicellular and a single fertilized egg of a multicellular organism, the results of what such cells produce suggests that they certainly might be complexities of different orders of magnitude, rather than the same.


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## Crowbar

Quote:


  Originally Posted by *rsaavedra* /img/forum/go_quote.gif 
_My point is that the results of what such cells produce suggests that they certainly might be complexities of different orders of magnitude, rather than the same._

 

It doesn't work out, since genes store only limited morphological information--more like guidelines for development. It's known that development of morphology is highly dependent on the organism's environment, with each cell's specialization strongly affected by what's around it. Even beyond birth this continues. Stereo vision does not exist in a newborn as the input from each individual eye is not fused until some time later. Prefrontal cortices do not complete development until the early 20s. There's been an estimate that if all morphological specifics were gene-coded, one would need several orders of magnitude more DNA and that would physically not fit within the largest cell. It's a matter of possible information content, and there is no indication that there are orders of magnitude more non-junk coding in multicellular organisms' cells.

 I don't want to concentrate on this since the much more important point was that the extra complexity is not a measure of evolutionary success by any means.


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## rsaavedra

Quote:


  Originally Posted by *Crowbar* /img/forum/go_quote.gif 
_and there is no indication that there are orders of magnitude more non-junk coding in multicellular organisms' cells._

 

Ah, but there lies part of it. The differences in amount of "non-junk" might not be a good measure of the difference in complexity between the non-junks. I'm not just really thinking about morphology, but all the other things involved, timed apoptosis (cell death) for example, differenciation and precise population size for different cell types and so forth.


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## Crowbar

Quote:


  Originally Posted by *rsaavedra* /img/forum/go_quote.gif 
_The differences in amount of "non-junk" might not be a good measure of the difference in complexity between the non-junks._

 

Yes, but that information must come from somewhere. As I've noted, the extra information for multicellular complexity is largely environmental feedback guided by the genetic differences. One more line of evidence: protists are single-celled yet are still eukaryotes like multicellular organisms. Though single-celled, they are much closer to us phylogenetically than they are to bacteria or archaea.

 Think of this analogy: a fractal is infinitely complex but in the end can be compressed to a simple formula (of course, there are no true fractals in the real universe since space/time are not infinitely differentiable and so you can't have a physical equivalent of infinitely precise real numbers; they are just in our mathematical imagination).


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## regal

Quote:


  Originally Posted by *Crowbar* /img/forum/go_quote.gif 
_ Genetic screening of zygotes can prevent lots of suffering in the future. It's already being done by individuals for their own selfish reasons, and *what I'm after is that it should be regulated and controlled by international scientific organizations with the total human gene pool in mind*._

 


 The day some "international scientific organization" decides what sperm fertilizes my wife's egg is the day that our liberties are totally lost. Who wants to live in a fascists state like this ? Why the need to breed a superior race ? 



 When I hear "international scientific organization" I cringe. I supposed you would like to see the "independant thinking" gene removed from the gene pool. The "international scientific organization" or ISO surely doesn't want people thinking for themselves or questioning thier theories. I am sure Einstein would have never been conceived if left to this ISO. 

 Surely not Van Gohn he was a schizo, right? 

 And about 90% of the artists we listen to on our headphones would be artificially selected out because they have the "chemical dependency gene".

 What about people who have nothing but "bad zygotes", I guess they have to adopt. Do they get sterilized by ISO, to prevent contamination of the gene pool?

 What about the 16 year old girl that gets impregnated without your artificial selection. Force her to Kill the baby ?

 Where does it end? This is why fascism failed, and should never be repeated. 

 Why use a headphone forum as a pulpit for disguised propaganda?


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## rsaavedra

Quote:


  Originally Posted by *Crowbar* /img/forum/go_quote.gif 
_Yes, but that information must come from somewhere. As I've noted, the extra information for multicellular complexity is largely environmental feedback guided by the genetic differences._

 

I honestly think you are overestimating the impact of environmental feedback, and underplaying the role of genetic complexity and precision. Environmental conditions might not be too different for a human egg and a fungi, yet they achieve quite different end results, don't they?

 I'm not a biologist, but as a computer scientist I've worked with gene regulation elucidation related algorithms. It has been discovered that there is lots of complex logic in how genes work and co-depend, how some activate some others for example. There is a lot more complexity than simply "here's this sequence, assemble this protein accordingly." Some such regulatory mechanisms have been pin pointed in some relatively "simple" multicellular life forms (e.g. sea urchin.) Yet there are way too many unknowns about those mechanisms even for those simple life forms. Way much less is known about something as complex as a mammal, in particular, a human.


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## Crowbar

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_The day some "international scientific organization" decides what sperm fertilizes my wife's egg is the day that our liberties are totally lost._

 

No, I'm talking about screening already fertilized cells. Don't forget that any progeny you create is going to affect the future human gene pool, so your libertarian thoughts simply do not apply since by procreating you _are_ affecting other parts of humanity. More and more individuals are doing such screening, and my guess is that will actually have a worse effect than no screening at all, since it will tend to produce very similar people in the long run by selecting for a few specific attributes. But no intervention at all doesn't work as I explained before due to lack of any selection.

  Quote:


 Who wants to live in a fascists state like this ? Why the need to breed a superior race ? 
 

We don't, but as I already demonstrated, doing nothing will make the race inferior as detrimental mutations accumulate over time, without any selection to control them, and result in more suffering in the long run. It's not about improving humanity, but about at least maintaining a current level of gene quality, and at the same time an appropriate level of diversity.

  Quote:


 I supposed you would like to see the "independant thinking" gene removed from the gene pool. 
 

LOL! You're trying to brew more FUD against me than Microsoft about open source.

  Quote:


 ... 
 

The rest of your post gives examples that have to deal with misapplication, and you are making assumptions as to how I think it should be implemented. I don't see where you're getting this, since I never touched the issue as to what is selected for. I simply presented an argument showing some sort of artificial selection is necessary, not how it should be applied. Of course there are many potentials for abuse, but that goes for essentially everything.

  Quote:


 Why use a headphone forum as a pulpit for disguised propaganda? 
 

The subject came up, and I never shy away from any topic. Propaganda is based on spin, whereas I've presented logic. If anything, you're the one using propagandistic tactics such as the Nazi comparison, and as you see others in this thread have noted the same.

  Quote:


  Originally Posted by *rsaavedra* /img/forum/go_quote.gif 
_Environment conditions might not be too different for a human egg and a fungi_

 

Huh?!

  Quote:


 There is a lot more complexity than simply "here's this sequence, assemble this protein accordingly." 
 

Yes, but that information must be stored somewhere, and DNA is the primary storage mechanism (unless you're a retrovirus).


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## rsaavedra

Quote:


  Originally Posted by *Crowbar* /img/forum/go_quote.gif 
_Huh?!_

 

Yes I did mean that.

  Quote:


 Yes, but that information must be stored somewhere, and DNA is the primary storage mechanism (unless you're a retrovirus). 
 

No one has said otherwise. Precisely, I'm advocating the intricate complexity of mechanisms encoded in the whole genetic machinery of humans, over and above a simplistic interpretation of DNA being just sequences that tell how to make proteins.


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## Crowbar

Quote:


  Originally Posted by *rsaavedra* /img/forum/go_quote.gif 
_mechanisms encoded in the whole genetic machinery of humans, over and above a simplistic interpretation of DNA being just sequences that tell how to make proteins._

 

No one has said otherwise.

 This applies equally well to single-celled organisms; they deal with a complex environment.


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## regal

Quote:


  Originally Posted by *rsaavedra* /img/forum/go_quote.gif 
_Yes I did mean that.


 No one has said otherwise. Precisely, I'm advocating the intricate complexity of mechanisms encoded in the whole genetic machinery of humans, over and above a simplistic interpretation of DNA being just sequences that tell how to make proteins._

 


 Exactly. Mapping the human DNA is akin to dissecting a corspe, we have to know how all the genes function in vivo before we can start playing God. Gene function at the molecular level isn't the realm of biologists, no offense but Biology is nothing compared to real physical science like chemistry and physics. The biochemists and physical chemists with their NMR and computational protein simulations will uncover more about the human genome than some biologists theorizing about the "future" of mankind. You have to learn to differentiate between the acedemia self serving B.S. in science vs the real truly emperical stuff. Science is nothing without experiementations to backup hypothesis.


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## Crowbar

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_9/10 out of ten the guy with all the answers writing books being sold at Borders is not much of a scientist rather a theorists._

 

Once again you're BSing. The biologists I referenced are Nobel Prize winners for their work in genetics. What's not experimental? Experiments proved Watson's idea about the structure of DNA was correct, and so on, these are not random theories without evidence, unlike your assertions. Next thing you'll claim evolution is just a theory. I have an acquaintance biochemist that founded a biotech company in my city whose main business is exactly the type of simulation you mentioned, and he agrees with my views.
 In the end, nothing of what I have said here addresses my argument that without some type of selection, the gene pool will degrade over time. This is my core argument and you've not managed to touch it. All you're saying is that a solution will be very hard without abuse, but that is not an actual counterargument, for ****'s sake!


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## Buggs

Linkl


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## Buggs

Link


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## tiggers

Quote:


  Originally Posted by *Buggs* /img/forum/go_quote.gif 
_Link_

 

What's the big idea posting op-amp information in a thread on genetics?

 you'd think this thread would be a sticky or something?


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## Crowbar

Maybe his point was that the thread was so off-topic, that he made an off-topic post in yet another direction.

 One paper that I think was mentioned here before but didn't get much discussion is http://www.essex.ac.uk/ese/research/...%20testing.pdf
 It's Hawksford proposition of a distortion metric that seems significantly better than THD/IMD (though there isn't a related human study to see how well his metric correlates with perception).

 So, anyone have any comments on that? It would be interesting to try to run one's own amplifiers through such a testing procedure.


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## Freq Band

Forgive us if we outsiders are squishing your amoebic enertia.
 ---------
 When reading the first post in this thread (PPL), I came upon this section and link:
  Quote:


 Soundstage magazine describing how they test Amplifiers
http://www.soundstagemagazine.com/me...amplifiers.htm 
 

...and assumed the link would apply to the testing of how an amp "sounds".
 Silly me. Of course it was about the electrical testing they were speaking of.
 My mind was somewhere else.

 What is the end use of an amplifier, or any other audio component ?
 Did you answer.....as a means of listening to music ?
 Shouldn't the equiptment's final purpose be the proper place to judge it ?

 And once it has been deemed "worthy"......

 ......shut off the lights, ...........

 and listen.........

*to the music*.


 -------------
 see my thread and unscientific amp comparison blind tests:
http://www.head-fi.org/forums/showthread.php?t=233146

 =FB=


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## Crowbar

Sure, but you have to shut off the lights before you listen, a blind test is in order. Measurement people are indeed mistaken, in that their mistake is they measure with equipment that is not the human ear. But when you know which amp is playing, you are measuring with not just your ear as well--you are measuring partially with your psychological bias.


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## peelax

Quote:


 
 

I kind of agree, but what would actually happen if there is no screening? Such a large number of people will become such a burden on society it will not be able to sustain them? If that was the case then natural selection would come back into play as anarchy took over. If you do screening and mess it up then a disease could come along and wipe everyone out. The lack of gentic diversity could have serious consequences, we need alternative thinkers who verge on insane. Either way its pretty much the same outcome. I'm not sure you can really say (at the moment) that given the big picture it would be a good idea to do anything, or ever do anything, over doing nothing.


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## ppl

As intriguing as the forgoing off topic discussion is I am going to refer you guys to this Link for some more thinking on the Amplifier Genome project. Some people operate primarily in the "Subjective domain"


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## melomaniac

see here for some engineering info and tests


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## OblivionLord

Im personaly all for what sounds good to my ears regardless if its subjective or objective.


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## 6RS

Quote:


  Originally Posted by *OblivionLord* /img/forum/go_quote.gif 
_Im personaly all for what sounds good to my ears regardless if its subjective or objective._

 

2x that! And I do not need double-blind tests to build my judgement.


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## kilgoretrout

Where can I find objective information on different DAC and how DACs across different price ranges compare with each other.


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## tldoxmf87

Thanks for the good information!


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## eruditass

this should be in the main forums


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## b0dhi

Great thread (except for the last few pages). I found it amusing that Crowbar was arguing how primitive the human brain is on the one hand, while on the other hand waxing lyrical about the great achievements of neuroscience. 

 It's also tempting to respond to the statement about having "nailed down" consciousness, but I find that endeavour tends to be like conveying the colour red to a blind person (before you say anything, yes, I'm aware that the physical correlates of the experience of colour are also evinced in the blind). 

 Back on topic, though, the site regarding memory distortion (here) was very interesting. The authours approach of subjective and objective measurement working together seems the best approach to me. Has anyone here built that amp? The schematic there seems to be partially incomplete.


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## NelsonVandal

Quote:


  Originally Posted by *b0dhi* /img/forum/go_quote.gif 
_Back on topic, though, the site regarding memory distortion (here) was very interesting. The authours approach of subjective and objective measurement working together seems the best approach to me. Has anyone here built that amp? The schematic there seems to be partially incomplete. 
	

	
	
		
		

		
		
	


	


_

 

I totally agree. This memory distortion is highly interesting. I've tried CFP as input stage in a couple of different amps and it makes wonder to the sound, more than any other tweak. As predicted "normally" configured current mirrors on the LTP sounds absolute CRAP (50 - 100R emitter resistors). Output stage affects the sound less than input etc. What I would like to explore is CFP applied to the folded cascode design, with JFET input and bipolars as "slave transistor".

 While I'm at it - this subjective thing - I'd like to say that choosing the right transistors for input, VAS and cascode stages determines if your amp will sound astonishing, dull or harsh, while the amp probably will measure exactly the same.


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## Kawai_man

Very interting thanks for posting this up


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