This I believe -

[esldude]

You are right. Usually, THD tests are made at either 400 or 1000 Hz and only the amplitudes of the THD are measured, not the spectral content. Sometimes odd and even harmonic distortion content are characterized and differentiated in the specs but not often.

 

 

 

 

Depends on to what degree two amps measure the same. Obviously two identical amps of the same model from the same manufacturer are going to measure and sound identical because every measurement possible will be identical between them. But the chances of two disparate amps measuring identically everywhere, are pretty slim, no matter how similar they are topographically.

 

 

 

It's not that published specs are misleading, it's just that, for the most part, they don't tell the prospective buyer much that is actually useful to him. Other than power output, what do the specs tell us? Well, distortion at some power output (usually the amps "rated" power), for one. But that's pretty useless and ambiguous if you think about it. I've seen subjective reviews of amps with what I would consider unacceptably high amounts of THD, where the amp was hailed as among the best sounding amps on the market! Clearly that's a useless specification. Frequency response? Show me a modern solid-state amp that doesn't have "DC-to-daylight" frequency response specs? Do these correlate anything that will give the buyer even a clue as to how the amp will sound? NO. Specs can be interesting, and they can give savvy engineering types some insight into the design decisions made by the manufacturer (depending on how comprehensive the published specs are), but the specs won't even tell these people how the amp sounds reproducing music. The only way to find that out is to listen.

 

Now, in this day and time, it is unlikely that any amp on the market is going to sound bad, specs or no specs. What you will get is distinct, subtle "flavor" differences between different amps. Sort of like tasting a bunch of different premium bourbons. Van Winkle's, Knob Creek, Woodford Reserve, they all taste different, but all are within the overall taste profile of being a pretty good bourbon. The same is true of modern amps. Go up in price (with both bourbon and amps) and you can expect more "refinement", but the whiskies still taste like bourbon and the amps still sound like clean, modern amplifiers.

 

When I am thinking of your conventional measures they are done right. No single THD number at 1 khz. I am thinking THD from 20-20khz with power specified and load. Further for lower power levels as well. Same for IMD. Frequency response should also be fully specified. Stereophiles ampflifier testing usually shows all such matters.

 

I would also point out Richard Clark's $10,000 amplifier challenge. You showed up with any amp you wanted, and compared it to his. Level, and channel matched. Within the power capabilities of both amps, with no more than 2% distortion from 20-10khz. Channel separation of 30 db and flat response to 20khz. You pick them in two consecutive ABX tests you win $10k. You don't you lose nothing. Reportedly more than 2000 people attempted it over 15 years. No one came away with the money. These are much less stringent requirements than I would have. Just another one of those times when taking away the sighted aspect of listening so many reported differences vanish.

[sdolezalek]

Measurements is most powerful tool for sound improving during development hardware and software.

 

Hearing is unstable tool for it.

 

Full measurements list is very long. For estimating audio apparatus/software need united considering all parameters / responses contained in list (as single complex). For marketing purpoces showed only famous characteristics.

 

Yuri: I don't disagree, but is the problem with hearing that no two ears hear the same thing or is the ear just a bad measuring device?

 

I suspect ear-to-ear variability makes equipment measuring more desireable, BUT, how do I know which set of measurements MY ears will like best? Or perhaps you believe that "best" measured system should sound best to all ears?

[senorx]

I believe:

 

Many say they hear things and differences that I've never heard, even before my hearing signed off at 15khz;

 

It is the supreme irony that this hobby is so heavily populated by old deaf guys like me;

 

The fact that I can't hear the difference between so-called mid-fi and hi-fi has saved me a boatload of $;

 

I'd rather listen to a great song with crappy sound than the reverse.

[beanbag]

That's not exactly what the "Carver Challenge" was demonstrating. I was in attendance at one of the Carver Challenge demonstrations and it wasn't about specs, it was about nulling-out nonlinearities in two disparate amplifiers (a Carver SS amp and a conrad-johnson tube amp) to the same degree of audibility (or rather to the same degree of silence) to show that an amplifier's signature sound was a product of it's nonlinear behavior. Carver's point was that if you make two amplifiers' nonlinearities equal in volume when all but the nonlinearities are removed from the signal, then the two amps will sound the same. I don't recall Bob measuring anything. He just used a comparator of his own design to invert the original signal and mix it with the non-inverted amplifier product in equal proportion so that only the difference between the original and the amplified signal remained.

 

It was a differential measurement

[kumakuma]

I'd rather listen to a great song with crappy sound than the reverse.

 

+1^1

[ted_b]

This I believe - That computer audio is still in its infancy, and that curiosity is the most important aspect of this infancy. Curiosity begets discovery; discovery begets advancement.

I would never have believed, even a few years ago, that things like galvanic isolation, apps on a NAS, DLNA or Schumann resonance would have anything to do with me enjoying music as I do now. I am revisiting my entire large collection due to the above mentioned (and in some cases completely counter-intuitive) aspects of this hobby. Measurements are important verifiers, yes, but some things we yet do not know how to measure (and I believe some things we measure are likely not the right things). So yes, bits are bits...but there is so much more. It's exciting, really.

 

Since posting this a couple days ago I have gotten more than one PM remarking that they were quite surprised I am against science and measurements! ?? I clearly did a horrible job explaining my beliefs. I am quite pro-science, to the point where I believe we have lots yet to discover scientifically that may prove why some things in our hobby are perceived today as anomalies or magic. Take for example, in another (much more serious) field, bone marrow/stem cell transplants. Only 10 years ago this way-more-highly-studied (than audio) field tested for only 4 markers in our blood; today they test for 10. Why? Some were not measurable at the time. T cells and B cells were less studied, etc.

 

My cry out is for more science, frankly; more discovery, less laissez faire attitudes (or worse, flat earth attitudes) that the only thing that matters, for example, are ones and zeros. I'm sorry if folks thought I was trying to legitimize magic or minimize measurements. Conversely, the "if it can't be measured it doesn't exist" is a dangerous attitude. My brother in law with a relapse of leukemia would be dead today. He's, instead, alive and kicking. And loving music.

[Cycleman]

This I believe:

 

That playing an album I used to listen to a lot -- but haven't played that much in several years -- on my now-best-music-system-ever-in-my-home is a source of true revelation.

 

Dave, who also agrees with Melvin's post above about the central importance of speakers

[Cycleman]

This I believe:

 

That the small size of many companies the audio industry, where a regular non-audio-professional like myself can have personal contact with -- and ask questions of -- the creators of various components, brings a form of pleasure.

 

Dave, who has asked various questions from the people who run several of the companies that make products listed in his signature such as DeVore Fidelity and Audience and Burson and Black Cat and TotalDac

[elcorso]

On this day on everything is the same, also boy and girls, isn't? Even inflatable girls...!

 

I stay on: "Vive la Différence". A very small one for some guys, but very important to me.

 

Cheers!

 

Roch

[ted_b]

This I believe:

 

That playing an album I used to listen to a lot -- but haven't played that much in several years -- on my now-best-music-system-ever-in-my-home is a source of true revelation.

 

Dave, who also agrees with Melvin's post above about the central importance of speakers

 

+1

 

Nice avatar btw; looks like my Duffy.

[Cycleman]

This I believe:

 

If this poll that leads off this thread stated "Audio cables CAN make a big difference in the sound of my system" instead of just "Audio cables make a big difference in the sound of my system" he would have put a check in the box next to that statement.

 

Dave, who says it depends

[elcorso]

Since posting this a couple days ago I have gotten more than one PM remarking that they were quite surprised I am against science and measurements! ?? I clearly did a horrible job explaining my beliefs. I am quite pro-science, to the point where I believe we have lots yet to discover scientifically that may prove why some things in our hobby are perceived today as anomalies or magic. Take for example, in another (much more serious) field, bone marrow/stem cell transplants. Only 10 years ago this way-more-highly-studied (than audio) field tested for only 4 markers in our blood; today they test for 10. Why? Some were not measurable at the time. T cells and B cells were less studied, etc.

 

My cry out is for more science, frankly; more discovery, less laissez faire attitudes (or worse, flat earth attitudes) that the only thing that matters, for example, are ones and zeros. I'm sorry if folks thought I was trying to legitimize magic or minimize measurements. Conversely, the "if it can't be measured it doesn't exist" is a dangerous attitude. My brother in law with a relapse of leukemia would be dead today. He's, instead, alive and kicking. And loving music.

 

+1

 

Don't worry be happy!

 

Those people seated on an inamovible status quo doesn't help the science to progress.

 

Cheers,

 

Roch

[TimU]

This I believe - Taj Mahal should be inducted into the Rock and Roll Hall of Fame.

 

Agree. It's not going to happen, though.

 

I saw him last year; he is still bringing it.

[Allan F]

That being said however, flatearth and cable-sound do share the same 'truthiness' level in my book. And I assume that is a potential inflamatory remark.

 

Please don't become a troll. We have had to put up with more than a few of those before they were eventually banned.

[kumakuma]

This I believe:

 

That playing an album I used to listen to a lot -- but haven't played that much in several years -- on my now-best-music-system-ever-in-my-home is a source of true revelation.

 

Dave, who also agrees with Melvin's post above about the central importance of speakers

 

So true. I believe that one of the main benefits of computer-based listening is the ability to access one's entire collection at any time.

[Paul R]

This I believe:

 

If this poll that leads off this thread stated "Audio cables CAN make a big difference in the sound of my system" instead of just "Audio cables make a big difference in the sound of my system" he would have put a check in the box next to that statement.

 

Dave, who says it depends

 

(grin) I would have to say that is a binary question Dave - they either do or they do not. But in truth, I worded it that way in an attempt to be non-antagonistic.

[trithio]

. I've seen subjective reviews of amps with what I would consider unacceptably high amounts of THD, where the amp was hailed as among the best sounding amps on the market! Clearly that's a useless specification.

My interpretation is very different:'clearly that's a useless review'. Maybe numbers do not tell everything but a crappy THD is going to sound crappy. But then, there are people who like crappy

[gmgraves]

Well, I wasn't there, but the article told a different story about him not measuring things. I mean how would he make changes without measuring. He was described as having 15 cartons of parts and measuring equipment in his hotel room. Here is a paragraph from that article:

 

The hotel room was a shambles! Across one end was a long table buried in oscilloscopes, distortion analyzers, voltmeters, the two amplifiers, a soldering iron, a white noise generator, two unidentifiable chasses full of inductors, resistors, and capacitors, a large table fan (there was no air conditioning), a half-dozen partially-drained Diet Coke cans, and perhaps 50 feet of audio cables, test leads, and clip-lead interconnects. The adjacent sofa and table were covered with countless little plastic bags of resistors and capacitors, several schematic diagrams, and sheets of paper crammed with arcane numbers and calculations. On the floor under the table was a Rogers LS3/5a loudspeaker which appeared to be connected to both amplifiers at once.

 

I believe it later said he managed a 70 db deep null between the devices. The final tweak needed to get that being to diminish the low end response of the Carver amp.

 

 

Oh, I don't mean that he didn't measure anything, I meant that he didn't measure the normal specs on the two amps he was comparing (which is what I thought you were referring to when you said that Carver's test shows that "Two amps that measure the same will sound the same"). Perhaps I should have been more precise. He didn't measure frequency response, distortion, power output, and those other standard tests. He did measure other things, at the individual gain stages stage and the component level (he even used a bridge to measure and compare resistor values, according to JGH!). His point was not to get the amps to measure the same, per se, but to null-out the nonlinearities to the same degree.

 

I should also point out that I was not in attendance at the Stereophile demonstration in Santa Fe, I was at a demonstration he set-up at a CES show subsequent to the Stereophile shootout. Since he had already done most of the work - probably several times - he had streamlined the process considerably. I witnessed the CES demonstration with Gordon Holt who was present for the Sante Fe "Challenge", and he told me that the original one took hours to accomplish. The demonstration that I heard took only a few minutes. But it was quite spectacular. The 'stock' Carver amp and the C-J amp sounded nothing alike until he substituted another Carver amp that had been "nulled" to greater than -60 dB (IIRC), and they did sound alike as far as I could hear.

 

Sorry for any confusion.

[gmgraves]

My interpretation is very different:'clearly that's a useless review'. Maybe numbers do not tell everything but a crappy THD is going to sound crappy. But then, there are people who like crappy

 

 

This was the original Jadis amplifier and the review was in TAS. The measured THD at full power, if memory serves, was something on the order of 2.5% (unacceptable to me, generally speaking). HP used the Jadis amp for his reference for a long time and said that it was the most musical amp he'd ever heard at that time. I don't believe that TAS, or HP, irrespective of what one thinks of either of them, is going to rave about an amplifier that was, in any way, sonically flawed.

 

Besides, I suspect that the 2.5% THD figures were at the amp's rated output. For all we know, just a few watts under that rating, the THD drops to fractions of a percent. This was what I was trying to show: That the published specs aren't all that useful in determining amplifier sound quality.

 

I also know a guy who has one of those Chinese Yaqin MC-100B Dual-Mono 100 Watt/channel integrated amplifiers. While it's an impressive looking bit of kit as far as it's build quality and looks is concerned (with it's four big transformers and chrome-plated chassis), especially for it's price of well under US$800, it does have a reputation for rather high THD (out of there box). Yet, in my acquaintance's system, it sounds damned good. He's measured the distortion and yes, it does top 1% at around 100 Watts, at normal listening levels, the distortion is less than 10% of that figure. Since then, I believe, he's applied one of the modifications that can be found on the Web that reduces the THD considerably. I haven't heard it since he's modified it, so I can't say whether the improvement was audible or just measurable. He bought his from Canada for a smidgen less than US$500, so it was quite a bargain. They're more than that now.

[Miska]

Speaking for myself, I would say any two amps that null to better than -60 db will sound the same. This with the actual speaker loads mind you.

 

First of all, null with what test signal? 1 kHz sine? 19+20 kHz IMD test signal? Something else?

 

For example, you could have two amps that null nicely with 1 kHz sine input, but not with TIM test signal. This thread reminds me of the 70's when everybody was competing about having lowest THD values and engineers didn't believe when listeners still said that the amps sounded bad. Most engineers didn't believe that the amps weren't perfect until Matti Otala published first paper about TIM (Transient Intermodulation Distortion) and later lot more work on the subject, including the "Otala & Lohstroh amplifier"...

 

 

P.S. Does someone still remember the Harman/Kardon Citation XX amp?

[gmgraves]

Since posting this a couple days ago I have gotten more than one PM remarking that they were quite surprised I am against science and measurements! ?? I clearly did a horrible job explaining my beliefs. I am quite pro-science, to the point where I believe we have lots yet to discover scientifically that may prove why some things in our hobby are perceived today as anomalies or magic. Take for example, in another (much more serious) field, bone marrow/stem cell transplants. Only 10 years ago this way-more-highly-studied (than audio) field tested for only 4 markers in our blood; today they test for 10. Why? Some were not measurable at the time. T cells and B cells were less studied, etc.

 

My cry out is for more science, frankly; more discovery, less laissez faire attitudes (or worse, flat earth attitudes) that the only thing that matters, for example, are ones and zeros. I'm sorry if folks thought I was trying to legitimize magic or minimize measurements. Conversely, the "if it can't be measured it doesn't exist" is a dangerous attitude. My brother in law with a relapse of leukemia would be dead today. He's, instead, alive and kicking. And loving music.

 

 

+1!

 

But audio has developed such a bad reputation for crack-pottery and snake-oil products, that serious scientists seem to steer clear of researching any phenomenon that even smacks of audiophile-ery! Most of what we know, scientifically, about music reproduction and psychoacoustics came from Bell Labs in the 1930's and 40's and RCA Labs and Harry Olsen in the 1950's. Neither of those two research organizations exist any more and it doesn't look like anybody has taken-up the cudgels since. Modern engineers and "scientists" in the field of sound are too busy working on new products to spend any time looking into why we hear what we hear.

[gmgraves]

First of all, null with what test signal? 1 kHz sine? 19+20 kHz IMD test signal? Something else?

 

For example, you could have two amps that null nicely with 1 kHz sine input, but not with TIM test signal. This thread reminds me of the 70's when everybody was competing about having lowest THD values and engineers didn't believe when listeners still said that the amps sounded bad. Most engineers didn't believe that the amps weren't perfect until Matti Otala published first paper about TIM (Transient Intermodulation Distortion) and later lot more work on the subject, including the "Otala & Lohstroh amplifier"...

 

Absolutely. I had a Crown IC-150 preamp once with so many zeros between the decimal point and the number (for the THD figure) that one got tired counting them. The preamp still sounded LOUSY! It did have one good feature though, the IC DIPs (two LM301, the reason why it sounded so bad) were socketed and therefore interchangeable. since the industry adopted the LM301 pinout as standard, every time op-amp technology took a leap, you could swap out the current ICs for new ones and you would have a new preamp. The last mod I made on mine before selling it to some college kid, was to replace all the capacitors with "WonderCaps" (audio quality polypropylenes). By that time, using high-slew rate FET input op amps, the line stage on the IC-150 was sounding pretty contemporary and at least as good as a Hafler 101! Getting rid of the high amount of TID and dielectric absorption distortion made all the difference.

 

P.S. Does someone still remember the Harman/Kardon Citation XX amp?

 

Yep. Sure do. 250 WPC, wasn't it? I reviewed one once. I remember that it was impressive in build quality and that it sounded very good, but I was put-off (at the time) by the fact that the speaker connectors wouldn't take banana plugs; just spade lugs and bare wire. Also, didn't the Citation XX only have XLR inputs; no unbalanced RCAs?

[esldude]

First of all, null with what test signal? 1 kHz sine? 19+20 kHz IMD test signal? Something else?

 

For example, you could have two amps that null nicely with 1 kHz sine input, but not with TIM test signal. This thread reminds me of the 70's when everybody was competing about having lowest THD values and engineers didn't believe when listeners still said that the amps sounded bad. Most engineers didn't believe that the amps weren't perfect until Matti Otala published first paper about TIM (Transient Intermodulation Distortion) and later lot more work on the subject, including the "Otala & Lohstroh amplifier"...

 

 

P.S. Does someone still remember the Harman/Kardon Citation XX amp?

 

Yep, I remember the Citation XX. Was buying one once, but the jerk sold it to someone else who offered more than his asking price (which I had agreed to and was on my way to pick up).

 

I would start with 1khz just to see if the levels can be matched. Then white noise and then pink noise for my initial steps. Then see what the 19+20 khz IMD looks like. If that looks good, then play some music. But if those all nulled out nicely the music won't be much of an issue.

[esldude]

Nice pics of a Citation XX.

 

Harman/Kardon Citation XX on thevintageknob.org

 

Harman Kardon Citation XX Amp and X-II Preamp for sale!!

[Superdad]

On this day on everything is the same, also boy and girls, isn't? Even inflatable girls...!

 

I stay on: "Vive la Différence". A very small one for some guys, but very important to me.

 

Roch: I think something got lost in translation with your comment. Are you saying that guys with big power amps are small in male anatomy? I resemble such a remark!