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In Reply to: RE: Here is the problem with this analogy. posted by Ralph on November 12, 2015 at 13:57:20
...good sound and good technical performance aren't mutually exclusive and there are real-life examples out there.
Follow Ups:
I don't know of one. But we have to be clear on what is meant by 'good'...
This thread initially was aimed, more or less, at Stereophile and their measurement regime. Mostly I think we can look at THD- if less than 0.005% at full power, that is good. Is 1.0% at full power bad?
I've yet to experience an amplifier with super low THD that sounds good. I would not mind hearing one that **did** sound good with distortion that low, but right now I don't think such a thing exists.
So as a result we have to deal with amps that are low in the distortions that the ear cares about, and are otherwise probably fairly high in the sorts of distortions that the ear does not care about. The latter however are likely to measure "poorly".
t
If what is meant by "good engineering" expects a super low distortion figure ala the claims made by JA elsewhere on this thread.
At the end of a review of at least 1 iteration of the 275, he wrote something like "Good engineering is timeless."
Jeremy
But I suspect it does not measure the way that JA would want to call it "good engineering".
However I am not saying it is not well engineered. Although I don't have direct experience with the new ones I have plenty of experience with the old ones and IMO they were well built and accomplished what the designer had in mind. Reliable too- definitely part of "good engineering"...
Well, but he did write the remark at the end of his measurements section, so I infer that it represented his reaction to what he measured.
Jeremy
he thinks its not "well engineered"?
Croft amp
"To me, it seems, at best, inadequately engineered, and at its worst-that nonflat RIAA response, the high levels of harmonic and intermodulation distortion-just plain inadequate."
Do read ST's response. :)
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...the Benchmark AHB2 as reviewed in Nov 2015 issue of Stereophile. You can read the review for yourself for details but THD+noise was almost beyond capabilities of test equipment. It also got a very good subjective review by Kalman Rubinson. Other reviews have resulted in similar assessments. All this with a tracking switchmode power supply no less. I haven't heard it personally but have no reason to doubt reviews at this point.
for more that 10 minutes without begging for a gun with which to shoot myself to end it all.
OK, it's an amplifier, not a DAC.
Never mind.
A friend of mine borrowed one some years ago...we had a similar negative impression. My inexpensive (but very good) Monarchy M24 DAC wiped the floor with it.
it's an amplifier with THX technology inside
Others, like Henry Wolcott have used a feed forward approach before and gotten similarly *wonderful* metrics. As have those using multi-rail power supplies.
It also got a very good subjective review by Kalman Rubinson.
"... but through a pair of Monitor Audio Silver 8 speakers, the sound was somewhat hard and thin. "
Yeah, give me more of that!
From the same review:
"Just because I found Benchmark Media Systems AHB2 not to be absolutely perfect under all conditions - after all, what is? - Doesn't mean that I want to represent it as anything less than a marvelous sounding amplifier. The AHB2 was capable of drawing more music from my B&W 800 Diamonds than I'd anticipated and mostly sounded better than the other amplifiers I've used to drive those speakers." .
Yeah, give me more of that!
I think "we" have a tendency to cherry pick data points out of context to support a personal POV.
I think "we" have a tendency to cherry pick data points out of context to support a personal POV.
Perhaps. I would never buy an amplifier, however, that sounds thin and bright - at any time.
Don't know quite where to go with that one so I'll pass. ;-)
Ah, so you haven't heard it yet and you put it forward as a good measuring and good sounding amp?? So what if KR liked it?
Are you saying KR's opinion is irrelevant or is it that the opinions of audio reviewers in general are irrelevant? Thin ice ahead!
BTW, he's not alone in his opinion as you must already know.
I am saying that you are putting forward this amp as a good sound/measuring amp and you haven't personally heard it. On top of that, KR found that the amp wasn't good in all situations (the Monitor Audio RS8 is not that hard of a speaker to drive). And on top of that, what KR uses for reference gear and tends to like is, IMO, rather unmusical and rather "hifi" ish gear.
I would like to know what someone like Martin Colloms or Art Dudley, or even Michael Fremer think of it before i would give it a second thought.
...You pretty much state that I err in putting forward an amp I haven't heard. However....by this reasoning isn't it also erroneous to dismiss the amp as you've done assuming you haven't heard it either? Seems I also have to conclude that you consider the opinions of reviewers irrelevant in general.
Curiously, you previously dismissed KR's opinion ("So what if KR liked it"), then you cite a portion of his review out of context in support of your personal point of view regarding the amp you haven't heard. You finish by stabbing KR thru his audiophile heart by describing his tastes in gear as "rather unmusical and rather "hifi" ish". The horror! This is all kinda inconsistent dontcha think? It also strikes me as cherry picking for best effect.
Even more curiously you state that you'd want Art Dudley's (or even Michael Fremer's - EVEN? yoiks!) opinion of the amp before giving it a second thought. I'll admit that I really like AD's style and outlook -followed him since the "Listener" days. However.......you must surely know that one of his reference speakers is a pair of Altec Valencias - possibly modified in undocumented ways. Have you ever heard these things? I have: I too am the proud owner of a pair of them. While dynamic and sometimes engaging, esp w/tubes, they're also colored with a "prominent" (shouty) midrange and rapid roll off above ~10-12KHz. IOW, "fun but fake". I don't begrudge AD for liking them but I also don't consider them reference quality, esp as a tool of the professional reviewer. If you can criticize KR for his "hifi" ish tastes in equipment..........
"by this reasoning isn't it also erroneous to dismiss the amp as you've done assuming you haven't heard it either?"
Except that it is a fundamentally wrong design from a psychoacoustic POV. Not to mention I have heard their other big product, the DAC, and it was frankly crap sounding. Given their design priorities and the methods they use to achieve them I can pretty safely conclude this amp breaks no new ground sonically.
"Seems I also have to conclude that you consider the opinions of reviewers irrelevant in general."
Where are you taking this from? Did I not state that there ARE reviewers whose opinion I value? Yes I did.
"This is all kinda inconsistent dontcha think? It also strikes me as cherry picking for best effect. "
How so? I said that I don't value his opinion and I explain that is largely two things A) He raves about gear that I have heard and find unmusical and not worth buying and B) His reference gear is largely made up of similar items, IMO. Nothing inconsistent with that and my dismissal of his Benchmark review.
"then you cite a portion of his review out of context in support of your personal point of view regarding the amp you haven't heard."
Where did I quote him at all? Perhaps you have me confused with someone else?
"I'll admit that I really like AD's style and outlook -followed him since the "Listener" days. However.......you must surely know that one of his reference speakers is a pair of Altec Valencias - possibly modified in undocumented ways. Have you ever heard these things? I have: I too am the proud owner of a pair of them. While dynamic and sometimes engaging, esp w/tubes, they're also colored with a "prominent" (shouty) midrange and rapid roll off above ~10-12KHz. IOW, "fun but fake". I don't begrudge AD for liking them but I also don't consider them reference quality, esp as a tool of the professional reviewer."
I said I value his opinion, not that I am a fan boy or want to duplicate his system. I have heard old JBLs and Altecs and some are amazing and some are as you describe. I haven't heard the Valencias. What you describe though doesn't surprise me. My Odeons sound completely modern in tonal balance and lack of coloration but have the fun and dynamics of one of these older horn systems.
You sure seem to reading a lot of your own interpretations into what I am posting rather than sticking with the facts about what I am writing...strange.
There have been tremendous improvements in SMPS units in the last 20-25 years so I don't discount a product that might use them.
However the specs look a little too good to be true and some of the claims on the website are pushing the envelope a bit; bottom line is we'll have to see on that one. I will look for it at upcoming shows.
So why no SET's Ralph or Hybrids, why only OTL's ......?
Go Rossi ......
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the "good technical performance" criteria is largely irrelevant.
The fact that any given amp may sound good has very little to do with the conventional metrics used to determine such.
It's a crap shoot when you base the determination on metrics which have little correlation with actual sound quality.
My point in the original post
.
...I was commenting on statements like this one: "The fact of the matter is that amps that 'measure well' don't do the best when dealing with the human ear/brain perceptual system. What they do well is look good on paper. The problem here of course is we don't experience music through paper, we experience it through our ears and brain." . Actually, the fact of the matter is that there indeed exist amps that measure very well AND are generally considered good sounding. i.e. Good measurements do not preclude good sound.
While it's probably reasonably true today that the correlation between good meas performance and good sound is mildly positive, IME, the correlation betw poor meas performance and poor sound is considerably more positive. Preference also has a role to play in this. I'm fairly certain a few of my audio acquaintances (and a noted reviewer for SP) find relatively higher levels of 2nd hd and amplitude compression very pleasing....not that there's anything wrong with that...
"While it's probably reasonably true today that the correlation between good meas performance and good sound is mildly positive, IME"
Earl Geddes actually found out that it is a slightly negative correlation but of course the R^2 is rather poor...so probably no correlation is more correct.
The only reason there is no correlation is that THD is nearly meaningless and so is IMD. The specific harmonic pattern IS significantly more important (See Gedlee metric or Cheever metric). This is the point that Ralph is trying to make. The metrics ALL indicate that low order harmonics even in relatively high % are benign and the higher order harmonics need to fall off exponentially to essentially zero. This monotonic PATTERN is more important than having very low, but evenly distributed harmonics that nearly all push/pull SS amps with negative feedback produce. This pattern is wrong to the ear/brain...if it wasn't then you would not have the poor correlation with THD and IMD that clearly exists.
Now, you claimed that there are some very good measuring amps that also sound very good. Care to name them? I have yet to hear one and I have heard nearly all of the top praised über SS amps, most of which measure tops. Ironically, the best sounding SS amps are the ones that measure somewhat poorly by the usual industry benchmarks (Pass, darTZeel, Vitus etc.). Please don't tell me that Soulution sounds good...I am not sure which psychadelic coolaid the reviewers are taking when they praise this brand...it just isn't on I tell you. Sure the latest and greatest SS beasts don't sound hard or etched like a poor SS amp from the past but they also don't sound really natural and still electronic or "hifi".
Based on psychoacoustics, NO push/pull amp, whether Tube or SS, actually qualifies as correct from an inherent design flaw...the cancellation of even order harmonics. That is usually further exaccerbated by the addition of negative feedback and Class A/B that further reduces low order even and odd harmonics and gives rise to an infinite series of high order harmonics. The maths are clear as are the measurements. With all due respect to Ralph, his OTLs are wrong as well but perhaps less wrong than most.
Nelson Pass also realizes this and his white paper on distortion is a very interesting read.
Given we have no truly linear amplification devices at our disposal (if we did then these discussions wouldn't exist) the best we can do is to "hide" the distortion behind our perceptive blind spots. SET done right gets the cloeset to mimicing our ear/brain pattern and puts those distortions in our blind spot...mostly. The only real downside to SET compared to other designs is power and cost.
For sure a short cut in SET execution will result in the bloated soft sound that many accuse the design for but it is the execution. A good output transformer that won't saturate within the power bandwidth is neither easy nor cheap to make. Making sure the driver doesn't distort before the output stage takes a sharp designer as well. Also, load line setting and parts matter because there is no negative feedback to squash it all out.
I was commenting on statements like this one:
Perhaps next time you might quote the text to which you are responding.
Good measurements do not preclude good sound.
Certainly not. Nor do they have any correlation to good sound. Usually the converse is true.
While it's probably reasonably true today that the correlation between good meas performance and good sound is mildly positive
If you refer to THD measurements, I find the converse to be true. Those with "heroic" distortion metrics (via boatloads of "corrective feedback") usually sound unnaturally lean and flat dimensionally.
Setting aside good measured performance, does poorly-measuring equipment sound good despite that or because of it? Is there some quintessence of music that can only be conveyed by less-than-stellar objective performance or does that poor performance add something that makes it sound preferable?
Steve O thinks that there is a stronger correlation between good reviews and poor measured performance than between good reviews and good measured performance. And, in regard to THD, you agreed with him.
Not wishing to put words in anyone's mouth, but the point then is that if well-measuring equipment can sound good it is more likely that poorly measuring equipment is preferred for what is adds rather than what well-measuring equipment cannot do. So, in those terms, measurements do matter.
"it is more likely that poorly measuring equipment is preferred for what is adds rather than what well-measuring equipment cannot do. So, in those terms, measurements do matter."
This is not the case. What is defined as "poor" measuring is that it has a somewhat high THD or IMD compared to "state of the art" but if the harmonics are in the human perception "blind spot" then it is acutally the other way around in terms of which product has good measurements. Those that measure poorly are high in low order harmonics relative to high order harmonics...this is a pattern similar to one observed in nature. Those that measure well have disrupted this pattern because they have pursued the ENGINEERING goal of low absolute distortion rather than the SONIC goal of low to no higher order distortion.
.. it shouldn't become a hall-pass for designers to not do a good job.
You can't help getting high 2HD with something like a single-ended triode so how much care/knowledge does the designer really need? But, you are correct about it all depending what the goals are.
I do wonder whether high levels of consonant distortion are subjectively better subjectively because they mask-out dissonant distortions or because they just sound nicer on their own. But, in the great scheme of things, it probably doesn't matter too much.
Regards
13doW
". it shouldn't become a hall-pass for designers to not do a good job." If it measures good and sounds bad does the designer get a pass for producing excrement with good specs?
Define not doing a good job, please.
"ou can't help getting high 2HD with something like a single-ended triode so how much care/knowledge does the designer really need?"
Very much actually because the goal is to keep the distortion low order and prevent the rise in high order harmonics...this means a lot of care in the design of each stage of the amplifier and careful balancing of operating points, passive parts choice and most importantly using a great transformer (at least the best that is affordable for a given design price point). It is a lot harder than making a mediocre design and cleaning it up with copious amounts of negative feedback.
" I do wonder whether high levels of consonant distortion"
Let me be clear, there is no such thing as "consonant" distortion...all distortion degrades fidelity but some does much more damage at much lower levels than others. Read the articles in Stereophile by Keith Howard where he added different distortion patterns to different music selections. He found no added distortion was the best (no surprise) but he also found that some patterns were far worse sounding than others. The monotonic pattern that was championed by Hiraga was found to be the least offensive of the distortion patterns he tried. This is the same pattern that Cheever concludes should be the least audible and that Geddes data also corroborates. Now, ideally we have a linear amplification device that gives no additional harmonics or IM distortion but since all our devices are "bent" then that ain't going to happen.
JA often calls triodes without feedback "bent" but the truth is that the triode is the least "bent" of all amplification devices, with the BJT and the Pentode being the most "bent". That is the true reality.
I think the white paper from Nelson Pass regarding negative feedback is interesting and illustrates quite well what is wrong under the surface. You don't really get rid of distortion but you seem to just push it around...Crowhurst said that the result is a kind of signal modulated "noise" floor that will mask low level resolution and damage dynamics.
And yet , regardless of what you , me and others think, many more like class-d sound over SET sound, oops, so much for the theories.
Since it's all wrong, whats next ....?
Go Rossi ......
Edits: 11/13/15 11/13/15
What I find is this:
Tubes and SS...
"Vocals are run through passive Renkus Heinz mono PA with Cary Audio Hi-Fi tube amplifier...
The other end is a two channel hi-fi playback system with Revel Saloon II speakers coupled with Levinson solid state, bi- amps. Rogue Audio tube pre - amp, Benchmark DAC , Esoteric transport and Sony Media Server. "
"I've owned numerous equipments..."
Start about 9:55. And none of it class D. :)
There is a room with Wilson Alexandrias in it. So, what does Dave Wilson use for making his recordings?
Answer here .
How about when Wilson shows their product at shows? Find out here .
Dave definetly know how (i have a few ) to make recordings , I'm also a big fan of prof Johnson reference recordings ....
!
Go Rossi ......
Edits: 11/14/15
if your point was simply the need for room treatments (to me an obvious requirement for any high performance system), then I heartily agree.
How many audiophiles spend big $$$ on the hardware and not the room?
I will bet Hypex has sold more ncore amps in the last 2 years than all the SET manufacturers combined....One would think that if they were all that, more people would be rushing to buy one...
No doubt SET offers something some people like, just as class d does. Trying to build a theory for their "superiority" is like trying to "prove" Thai food is superior to Italian....
It's also not necessary for enjoyment of one's hobby. I fail to understand the need to find some sort of rationale as a basis for the ownership of a certain type of equipment, or the need to belittle what others enjoy. I suppose there will always be those who need to feel superior, small and insignificant as it may be....
try it! you know you want to!
many more like class-d sound over SET sound
I have yet to meet someone who actually stuck with Class D. It definitely sounds different and for many that is good enough.
I know a lot of guys who tried it and tried to live with it though and all gave up on it.
I haven't given up yet, but if it takes 50K to hear what class-D sounds like,i will have to take Kurby's word for it..Have to sully myself with the usual bad SS stuff ... :)
Regards ..
Go Rossi ......
Edits: 11/13/15
For my own part, I think class D is the rising star in audio amplifier technology, but so far hasn't brought home the bacon. But that might be different tomorrow- the technology is still in a steep portion of the price/performance curve.
If you need $50K to understand what its about- well, traditional technologies need nothing of the sort to demonstrate what they do in spades. I think I'll wait too...
I think class D is the rising star in audio amplifier technology...
when implemented as a "Power DAC" or using other means (Devialet's current dumper/Stasis) to eliminate the prodigious amount of HF noise.
"Good measurements do not preclude good sound.
Certainly not. Nor do they have any correlation to good sound. Usually the converse is true."
If the converse is true, there is a correlation, a negative correlation, yes?
"If you refer to THD measurements, I find the converse to be true. Those with "heroic" distortion metrics (via boatloads of "corrective feedback") usually sound unnaturally lean and flat dimensionally. "
Not necessarily THD alone since there are other measures of linearity and maybe even good sound. Also not clear what you mean by "heroic". FWIW, an amp with low THD and other good traditional meas ( thru use of corrective feed forward ) is also getting tairly decent listening reviews too...the new Benchmark amp. I want a pair!
If the converse is true, there is a correlation, a negative correlation, yes?
Yes.
Not necessarily THD alone since there are other measures of linearity and maybe even good sound.
To wit?
To wit!: IMD, SID, smoothly decending levels of high order distortion products (there's name for this condition but it escapes me at the moment), basic stability, rapid overload recovery and so on. Optimizing any one or two parameters is probably insufficient so it's really an exercise of judicious balance. Much of this stuff was known and effectively dealt with in the middle of the previous century by a few designers.
Geddes found that IMD also has no correlation (actually slightly negative but statistically insignificant at the 95% confidence).
An interesting paper by Geddes. Since you've cited Geddes on a couple of occasions here, I assume you're familiar with his paper.
While I'm not qualified to directly butt heads with Mr. Geddes, what he describes in his paper raises a number of questions.
1. The testing methodology employed a 15 second excerpt from ALW's "Phantom of the Opera" ripped from the redbook CD and converted to a .wav file. This was considered "the reference". Is 16/44.1 sufficiently resolving considering the potential subtleties involved? Is the music selection sufficiently revealing? Is a 15 sec sample of sufficient duration?
2. Twenty one different stimuli (distortions) were mathematically simulated (calculated). The exact nature of the distortions is unclear as is the correlation of them to real life distortion generating devices. The calculated distortions were then used to multiply the input reference wav file to produce the test sample or signal. All stimuli were digitally adapted and presented to the subjects via computer...as 16/44.1 wav files. Is a mathematically generated distortion a valid means of simulating the performance of a physical device? Has this methodology been validated by Geddes or independently by others?
3. Subjects rate the test signals as better or worse than the reference. Doesn't this predispose the results towards "preference" instead of "accuracy"?
4. Geddes finds a weak negative correlation between THD and IMD and preference but essentially dismisses this finding based on statistics and pursues it no further. He also finds a moderate positive correlation between the proposed Gedlee measure (Gm) and preference. He then chooses to improve the statistics of Gm by throwing out three unsupportive stimuli. Is this appropriate?
5. The paper is 12yo. Has there been any independent validation of the methodology or verification of the results? Have there been any additional developments or refinements of the Gm concept since 2003? Is any independent mfgr using Gm in place of or as a supplement to more traditional measures? A quick web search turned up nothing but not being a member of AES may be a limiting factor.
Overall, I found Geddes' findings and proposal to be interesting. But really isn't this just one relatively old data point and another dead end in the search for a means of correlating objective device performance with subjective preference or "goodness" using one or two measures?
1) I would assume it was chosen specifically it's revealing nature and i think 16/44 is sufficient.
2) There is another paper that discusses the distortion in more detail (it is a theory paper).
3) No, preference is a better way IMO as it takes off some of the pressure of "do I hear" vs. "what do I hear".
4) I think the findings of THD and IMD mirror what a lot of audiophiles out there complain about. I do not think that what Geddes does with his own metric is all that valid (one data point maybe if it fails a Q test but not three). His metric suggests he is on the right track but the fact of a weak correlation means there is something missing from his model to make it more complete. Maybe Cheever's model would fair better? Apparently, Shorter's simpler model was not that effective either or maybe more would use it.
5) I found a more recent pub from a Swedish (or Danish) group that reached similar, but more difficult to understand, results
Based on the synthesis of all recent research I have read I reached the conclusions that I posted some time ago on the amp/preamp forum.
http://www.audioasylum.com/forums/amp/messages/20/208108.html
I stand by my analysis until such time that I hear something or see research that falsifies what I wrote.
I posted a link where you can take the test yourself ,
Geddes findings and research is valid, what is not valid is how much of it actually correlates to us in actual use , when one hears their favorite song vs non familiar music , our sensory system will and usually does change gears...Short of directly taking and using amplifiers with the distortion characteristics suggested by Geddes research with golden ear audiophiles , what are we really proving....
Regards
Go Rossi ......
Edits: 11/14/15
Geddes found that IMD also has no correlation (actually slightly negative but statistically insignificant at the 95% confidence)- Morricab
Go Rossi ......
nt
try it! you know you want to!
Yep, that's the one
That wasn't difficult, was it?
Much of this stuff was known and effectively dealt with in the middle of the previous century by a few designers.
Then such got lost when SS first arrived and the arms race for "better" metrics and worse sound was prevalent. :)
"Then such got lost when SS first arrived and the arms race for "better" metrics and worse sound was prevalent. :)"
Seems that way although I don't believe "worse sound" was an actual design goal back then. I'd guess that the degraded sound was the result of the pursuit of unbalanced objectives with advertisable power and distortion specs taking precedence at a time when SS technology was not well developed. I have to believe the better designers knew what was going on but weren't in a position to resist.
The problem is the outcome of the techniques used to lower distortion, namely push/pull and negative feedback. The outcome gives the desired ENGINEERING solution of low distortion but doesn't achieve the SONIC soluton of having a proper harmonic content for good sound.
I'd guess that the degraded sound was the result of the pursuit of unbalanced objectives
Absolutely and to the point of this thread - chasing metrics that fail to correlate with qualitative aspects of the listening experience.
Which continues today with some designers.
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