[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.

 

[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?

 

[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!

 

[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.

 

[JohnFerrier]

More good posts.


JF

 

[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.

 

[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.

 

[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

 

[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.

 

[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.

 

[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

 

[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.)

 

[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.

 

[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...

 

[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!