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Old 22nd March 2003, 02:32 AM   #11
mb is offline mb
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This is an account of a blind test, which is NOT rigorous, but has convinced me that I'm not just imagining differences between amps:

I've built an AKSA 55, with mild tweaks (Nirvana option + more). Recently I build a gainclone-like kit amp. I've been tuning the gainclone in the past 3 weeks, and it has been swapping places with the AKSA.

My wife sees me connecting / re-connecting amps, but has no interest in the hardware specifics, only in listening. Even then, she doesn't listen out for the audiophile qualities (don't talk to her about PRAT, soundstage, neutrality, ...).

In about 15 iterations, she has correctly identified the AKSA or the gainclone >90% of the time. On earlier occasions, she was able to identify between the AKSA and a Krell about 80% of the time.

Given that she is NOT looking at any power indicators or cabling layout, would this qualify as blind? Yes, levels are not calibrated, and the music varies, but to be able to discern over a relatively short listening period, AND consistently identify the differences in sound indicates pretty substantial variation in sound.
 
Old 22nd March 2003, 02:43 AM   #12
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Quote:
Originally posted by nw_avphile


The editors of Stereophile lost a blind challenge to Bob Carver. They couldn't tell a pair of $15,000 monoblock tube amps from a $699 Carver model that Bob lightly tweaked to duplicate the frequency response of the tube amps. They helped define the terms of the test. They were VERY confident they would win. They lost.

I bought that Carver amp because of thet challenge. I had it for about two years and sold it, because I couldn't listen to it. I had Zen amp in my system for 7 years and I could still enjoy it.

When test like that is conducted I suspect that the level of excitement is increased and the person tries too hard to choose the proper answer. The better way to carry it out would be when someone switches the amps (without person under test knowing it) but the amp cannot be visible and the person should be under impression that he still listens to his usual amp. If he won't notice that something changed, than I will believe that all the amps sound the same.
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Old 22nd March 2003, 02:50 AM   #13
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Quote:
Yes, levels are not calibrated
Then right there, you've made the test invalid. It's very well established (in blind tests!) that people can detect extremely small level changes (on the order of 0.1 dB). And it's equally well-established that if they believe that the levels are matched, they'll pick the slightly louder amp as sounding "better," and here I have some direct experience.

Doing proper listening tests is tedious, time consuming, and inconvenient for the experimenter (not necessarily for the subjects), so few people bother.
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Old 22nd March 2003, 03:11 AM   #14
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Default "A Nod Is As Good As A Wink To A Blind Bat" - LIfe Of Brian.

Hi Phred and Frank,
I agree 100% with you both, and Sy perhaps something is wrong with your test systems - inadequate speakers etc, etc.

I find it perfectly easy to discern minor sonic differences due to minor tweaks or modifications.
The key is to listen not in a 'N & THD testset' mode.

Let's be honest - just about any modern gear measures pretty damm 'perfect' on a test and measurement bench, however these tests usually do not look for differences in load dependency and mains power supceptability, and this is a key error.

I find the key is to listen in an 'FFT' mode, and to listen for micro 'patterns' in the sound.
This will reveal differing sonics due to differing dynamic behaviour, but takes practice using many types of music and many types of electronics to discern commonalities, and from this then discern fine differences.
Spectral and dynamic behaviours are the keys to listen for, and are the terms that describe the long term musical enjoyment factors.

In my experince just plugging an additional amplifier (not even turned on) into a common mains power board can alter the sound of a system, and this I expect is not a factor heeded in 'blind' testing, and in my view further invalidates conventional blind testing.

When you gain divining or dowsing sense, you are in a much better position to understand what your ears are trying to communicate to you.

Dowsing is about sensing small changes in levels and spectrums in ambient fields, and a similar mode of sensing needs to be applied to discerning differences in audio equipment.
Once you have developed these skills, then categorising audio gear is a piece of cake, and reliably so.

As Phred says not everybody is familiar with live music - acoustic or amplified rock, and indeed this is required as a proper reference.
A live mixing desk contains individual channel tone controls, and despite all inputs running and a cacophony coming out of the FOH speakers, just breathing on a tone control or level fader is clearly audible to experienced ears - indeed this skill is mandatory to achieve pleasant, coherent, musical and dynamic mixes.

The same comment above applies when adjusting the final FOH send graphic eq - changing just one GEQ band by half a dB is clearly discernable to discriminating ears.

To those who belive so solidly in blind testing, I say that the entire test setup and methodology needs to be examined very closely, and this very much includes the skill levels of the listeners.
If you take 6 bricklayers or boilermakers I would fully expect the results to tend toward 'chance' - 50/50.
If however the subjects are very experinced orchestral musicians or conductors, you then have a much more proper and reliable test.

Eric / - You just have to understand your own ears.
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Old 22nd March 2003, 03:23 AM   #15
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Quote:
Originally posted by Peter Daniel
When test like that is conducted I suspect that the level of excitement is increased and the person tries too hard to choose the proper answer. The better way to carry it out would be when someone switches the amps (without person under test knowing it) but the amp cannot be visible and the person should be under impression that he still listens to his usual amp. If he won't notice that something changed, than I will believe that all the amps sound the same.
You know, I can't think of anyone of note who has actually, literally claimed that "all amplifiers sound the same."

What I have heard some of note claim is that what causes amplifiers to sound different is no big mystery and rather trivially measureable, such as distortion, frequency response, level mismatch, etc., and that once these differences are narrowed down to below known perceptible limits then the two will be indistinguishable.

But of course once you tweak one amplifier or another in order to minimize its differences from another, you don't exactly have the same amplifier as you did originally.

So where exactly did this "all amplifiers sound the same" come from? It smacks of the same simpleminded rhetoric used by Republicans to characterize Democrats and vice versa.

Also, in "ABX" tests, the listener always knows the identity of A and B. This allows them to swtich from one or the other in order to attempt to discern any differences. Once any differences have been identified, then you can switch to X which will randomly be selected (for each trial, not each switch) to be either A or B.

Once a difference between A and B has been identified, then you can compare A and B to X. so for example if you switch from A to X and you hear no difference, but you hear a difference when switching from B to X, then logically X should be A.

If there is an actual identifiable difference, there should be no trouble in distinguishing it.

Tom Nousaine has set up a number of self-professed golden-eared audiophiles with an ABX comparator in their own home using their own system and allowed to run tests at their own leisure over periods of months or more.

So far, none have been able to statistically discern any differences once basic issues such as distortion, frequency response and level matching have been addressed.

Of course this isn't necessarily what I'd call definitive. But I have always been amused at how "night and day" differences tend to simply vanish once the listener is simply denied the knowledge of which component they're listening to.

They're absolutely sure they hear a difference when switching between A and B. And they're often just as absolutely sure when they compare to X. Yet when the results are examined, no statstically significant correct (or incorrect for that matter) responses seem to manifest.

I would like to think that anything described as "night and day" should be able to be distinguished 100% of the time seeing as there are many "subtle differences" which are easily distinguished by certain individuals 100% of the time in such tests.

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Old 22nd March 2003, 03:34 AM   #16
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Yes, Eric, that must be it. I've got crappy speakers.
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Old 22nd March 2003, 03:38 AM   #17
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Default The nulling test...the end of ...(i think it sound better)...

Retourning to the Hafler nulling tests my coments is:

This is my favorite test,that i use for so long...with it you can see all distortions ( invented or yet indiscovered)...it was amazing to do this test in some very expensive comercial amps.. hehehehe!
You can do the test even with music signals...and with a speaker load...in real conditions of operation!!
In a nutshell...if the input is equal to the output the amp desapear from the equation...as it is tottaly transparent...so time to look at the source and speaker!!
By the way...anytime that i improve a amp in the nulling test...i see also a improvement in sound quality...i think is hard to talk against this test..
But i don't beelive that all amps sound the same...as in the nulling test...they also don't show the same residual...

So simple and so true!!

But i wonder who is searching the truth in audio...just a fews!!

Cheers

Ps: Without a test like this how can we trust in a person saying..that sound good...
for me is the same that a person talk about food...for one is good...for the other with to much salt...for the other without salt at all...
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Old 22nd March 2003, 03:54 AM   #18
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Dear nw_avphile,

To answer your original question: for any assessment which is significantly influenced by psychological/experiential factors the DBRCT is the recognized and accepted "gold standard"..... period!

Anyone wanting to argue with the above statement (on it's own) is embarking upon a personal credibility crisis.

What you are saying is in principle absolutely true, however saying it here is borderline insanity. Those from a scientific background will support you and accept that before we claim to be able to hear "a, b, c, ... x, y, z", we should actually subject ourselves to a rigorous, controlled, blinded environment.

As you suggest, many of the "golden ears" would likely tarnish and excuses would abound.

The industry (as you rightly suggest) has way too much vested interest to ever allow this sort of madness to occur and will claim all sorts of "********" to discredit the process. The process itself remains valid (done properly - which is actually very hard!)

Me ...... well, I built a nice Aleph5 clone, used good quality parts and spent many hours lovingly creating this project. Does this mean it sounds better to me ........ HELL YES!!!

The inescapable truth is that psychological factors do alter our perceptions and appreciation of things in the real world. Our friend who bought the Carver because of the results of the blinded test was happy for a while. But, over time, knowing we are listening to a "modest" product must influence how we perceive it. I do derive more pleasure from my amp because I know I built it well and it is a "quality" product. this knowledge adds to my appreciation and enjoyment.

Would I bet my son's life that I could distinguish between this and another SE amp .......... not in this lifetime

Are there companies out there who are taking customers for a ride and profiteering from pseudoscience? ......... I'll leave this to your assessment.

Remember - at the end of the day, enjoyment of the music is the end requirement, and enjoyment is a multidimensional, difficult to measure thing

cheers,
mark
 
Old 22nd March 2003, 04:36 AM   #19
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to me, it's easier to spot differences than to identify specific sound signatures. The tasks involve two different ways of thinking/listening, quite possibly different sides of the brain are involved.

Since you seem to be into it why don't you try this test: with a bunch of people, play something on one system, then change a component and record differences between the two systems on a piece of paper. Compare notes at the end. I bet you'll find that most everyone will have heard the same difference in sound.
Report back, please.
 
Old 22nd March 2003, 04:42 AM   #20
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Originally posted by mefinnis
Remember - at the end of the day, enjoyment of the music is the end requirement, and enjoyment is a multidimensional, difficult to measure thing
Absolutely!

Which is why I ultimately have little interest in blind testing or whether my perceptions are due to physics, psychology or some combination of the two. I'm not so insecure that my ego is threatened at the notion of my being nothing more than a normal human being with all the mortal weaknesses that entails.

When it comes to enjoying music, I'm a "hedonist subjectivist." I don't serve any piece of equipment. I don't serve any blind test. I don't serve any measurement instrument. I don't serve the music. I serve only my own pleasure and satisfaction, regardless of how it may come about.

Well, provided it doesn't violate anyone's rights or liberties.

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