Op Amps: Horrible Truth

Vitaliy_Kiselev

MYTH: MOST OP AMPS SOUND DIFFERENT - There’s a general perception that op amps sound different. Many gear manufactures tout op amp brands and part numbers in their marketing literature. The $3 OPA2134 is supposed to sound much better than the $1 NE5532 and the $10 AD8610 is supposed to sound better still. But do they? The chip companies don’t help the perception implying some of their op amps offer better sound. But used properly, in a typical audio application, I’ll challenge anyone to a listening test and bet they won’t be able to tell the above three op amps apart. The only catch is it would be a blind test and the listener won’t know which op amp is which.

HISTORY: The Operational Amplifier (op amp) was invented in the 40’s. Bell Labs filed a patent in 1941 and many consider the first practical op amp to be the vacuum tube K2-W invented in 1952 by George Philbrick. Texas Instruments invented the integrated circuit in 1958 which paved the way for Bob Widlar at Fairchild inventing the uA702 solid state monolithic op amp in 1963. But it wasn’t until the uA741, released in 1968, that op amps became relatively inexpensive and started on the road to ubiquity. And they didn’t find their way into much consumer audio gear until the late 70’s and early 80’s.

MYTH: DISCRETE IS BETTER - For audio use the op amp’s main competition is a fully discrete amplifier made out of transistors, resistors, etc. Which is better? It turns out, for nearly all applications for which IC op amps are suitable, they easily outperform discrete designs in the following areas:

Better Performance – It’s very difficult to match the overall performance of even the inexpensive 5532 op amp with a discrete circuit. The discrete circuit is at a disadvantage in many areas including component matching, bias stability, and the need to use off-the-shelf components (every “component” in an IC op-amp can be custom tailored and optimized to its task).

Simplicity – To even come close to the performance of an IC op amp many more components are required. You need differential pairs, multiple stages, current mirrors, constant current sources, bias circuits, protection circuits, etc. You end up with dozens or even hundreds of components to try and match a single dual op amp IC in a little 8 pin package.

CMRR/PSRR – Common Mode Rejection Ratio is how well an amplifier can reject unwanted noise. Because their internal components are so well matched it’s easy for op amps to achieve excellent CMRR and PSRR (Power Supply Rejection Ratio) performance. This helps their real world performance in audio applications because they can reject noise on the power supply, and inputs, much better than most any discrete circuit.

High Open Loop Gain – Op amps typically have higher open loop gain. This allows more feedback which in turn lowers distortion. There’s another audiophile myth high feedback is somehow bad but that’s the topic of another article. Look up Bruno Putzeys recent article on the topic. He pretty much busts all the feedback myths wide open with real science. He even explains how so many people got off track. Trying to get comparable open loop gain in a discrete design typically creates challenging stability issues.

Repeatability – Op amps have tightly controlled specifications and detailed information available on their performance. They’re typically individually tested when they’re made so you know exactly what you’re getting. You can buy a TI 5532 today and an On Semi 5532 a year from now, and both will perform very similarly. High performance discrete circuits often require matched or hand picked components to achieve their best performance. This makes them difficult to reproduce and their real world performance is more of an unknown and sometimes requires detailed testing of each implementation (something few DIYers can do). Discrete circuits also typically cannot hold as tight of performance over a wide temperature range.

Massive R&D – The big semi conductor companies compete against each other for design wins. They spend serious money trying to out perform each other and have million dollar labs full of advanced equipment. They design the ICs right down to the properties of each transistor and have at their disposal types of internal components that are not even available as discrete parts. It’s impossible to match all their capabilities with a discrete design.

Built In Protection – Many op amps have at least current limiting and some also have other forms of protection like thermal shutdown. This makes them more robust than a discrete circuit unless similar circuitry is added to the discrete design making it even more costly and complex.

Ease Of Use – Op amps are very well characterized and typically well supported by the manufactures with detailed specs, performance graphs, and even application notes and sometimes reference designs. Following their guidelines usually results in predictable performance. They’re also typically easier to “glue” together when using a proper bipolar power supply as the outputs are referenced to zero volts and can be directly coupled to the next stage. The discrete designer is largely starting from scratch and has far more hurdles to clear.

Lower Power – An op amp, because of all the advanced techniques available to IC designers, can operate its output stage in Class-B with vanishingly low levels of distortion. While discrete designs are often forced to use much more power hungry Class-A to even come close. Overall, an op amp typically needs substantially less power than a typical discrete equivalent. This is a huge advantage for battery powered gear or if you need lots of amplifier stages.

Lower Cost – You can get amazing performance for under a $1 with an op amp. You can’t even come close with discrete designs. In fact, discrete designs often end up significantly compromised to limit their cost and complexity to reasonable levels. So you end up comparing a highly optimized IC against a compromised discrete circuit that still costs a lot more and performs worse.

Rest at http://nwavguy.blogspot.ru/2011/08/op-amps-myths-facts.html

Some measurements at http://nwavguy.blogspot.ru/2011/08/op-amp-measurements.html

trevmar

It is a pity that so much knowledge has disappeared over the past decade, as the Baby Boomers have retired, or passed away.

I don't have time to even begin to detail the mistakes in that blog, except to say that in the 1980's I designed a number of very high fidelity discrete component HiFi amplifiers - which did sound better than op-amps at the time. More importantly - they measured better as well. Cold hard parameters. Parameters missing in this blog.

See, for example http://trevormarshall.com/old_papers/Series-4000-Stereo-Amp-ETI.pdf Sadly, even I have lost the initial articles from that series, the articles showing Intermodulation performance.

"Intermodulation distortion," "Transient Intermodulation distortion," the ear's preference for even harmonics over odd, all these make a difference. Not a big difference, but a difference.

The mere fact that anybody can pretend to hear differences between amplifiers tells us that something is wrong. There should be no difference at all, yet there is indeed a lot of difference. Why? If any half-decent op-amp can do the job properly (as alleged in the above blog)?

Having said that, I currently use a switched power amplifier as my "reference standard" for audio, driving some amazing omnidirectional speakers through a mini-DSP for digital equalization and compensation. There are a heck of a lot of op-amps in that signal chain :) :)

http://trevormarshall.com/class-d-tutorial http://trevormarshall.com/ground-effect-omni/

There is nothing fundamentally wrong with the new technologies, but to close our eyes to the differences, rather than be aware of the limitation (and avoid them) is not the way to advance technology...

Vitaliy_Kiselev

I don't have time to even begin to detail the mistakes in that blog, except to say that in the 1980's I designed a number of very high fidelity discrete component HiFi amplifiers - which did sound better than op-amps at the time. More importantly - they measured better as well. Cold hard parameters. Parameters missing in this blog.

I think it is whole point to detail problems if you see them and have scientific and measurable proof.

Looking at PDF I do not see anything outstanding.

Today big analog amplifiers are mostly audiofiles area were esoteric terms are used to describe sound. And big money are at stake.

Whole point of blog post I referred were to break huge business on op-amps mods and op-amps stated difference, mostly in headphone amplifiers (also huge and very dirty business).

svart

I agree 100%. Since I do audio gear design on the side, I've always been interested in what makes gear "good" or "bad" according to the person who acquires it.

Chances are that the person has bought the hype surrounding certain gear, mostly around antique discrete gear. They focus on the discrete aspect but fail to take into account the whole design. Parts back then had much higher distortions and the decoupling was a lot worse, thus leading to a lot of different types of artifacts that people actually like to hear. Modern opamps were designed specifically to NOT have these artifacts and therefore don't have the "mojo" that the old parts do.

I used to frequent a DIY audio forum many years ago and the mis/disinformation became too much to bear, so I left. It became all about selling things to others and not trading good information anymore.

One of the worst was the opamp upgrade sale. So many people would come to the forum and want to upgrade their opamps simply because of so many others who heard magical transformations in their cheap crap gear after only changing a single part. A lot of people quickly jumped on the bandwagon and unless you were using certain opamps, there was no way your audio would sound good. Next came the folks doing the upgrades selling the same agenda to make money.

I did my own studies and found that I rather preferred the humble NE5532 and biploar electrolytic caps in my mixer rather than buying insanely expensive super-duper audiophile quality opamps and esoteric caps, and/or specialized things like DC servos and such.

Personally, I've always found the best way to upgrade cheap gear is usually to increase the local decoupling on the opamps and the bulk decoupling for the local opamp groups. Cheap gear tends to really lack in these areas. Most designs that use "cheap" opamps like the NE5532 also cheapen out on the power supplies and decoupling, so people who listen to these usually unfairly blame the active part instead of the supporting circuitry.

Vitaliy_Kiselev

Personally, I've always found the best way to upgrade cheap gear is usually to increase the local decoupling on the opamps and the bulk decoupling for the local opamp groups. Cheap gear tends to really lack in these areas. Most designs that use "cheap" opamps like the NE5532 also cheapen out on the power supplies and decoupling, so people who listen to these usually unfairly blame the active part instead of the supporting circuitry.

Best option is do not touch anything and (only if this part is really defective!) send it back or return. On worst case, sell it adding something about "soft second harmonics rich tube tone" :-) And got properly designed thing.

Time waste of such things is just horrible, as result in 99% cases is worse than default.

If you want to improve sound you need to change speakers (or headphones) first.

Also for some guys beating their head against good wooden door improve sound significantly :-)

DrDave

I have a lot of gear that was designed so that you can just pop out the op amp and pop in another one. You can definitely hear the difference. I'm not saying one sounds better than the other, they just sound different. Some of them are clearer, some are warmer, some capture fast moving transients better. I think the whole "scientific" thing would be like choosing a video camera purely based on the DxO mark. Why would you do that?

I have definitely heard some NE 5534/5532 designs that sounded good, but I like the Grace discrete OpAmp the best, and I have LM, AD & THS in my preamps. The LMs may not be the best around, but I don't see any reason to upgrade. But if I want to upgrade, just order the part and pop it in the socket.

However, since my FR2LE (NJM 2122 OpAmps) and DR 680 sound fine with their stock opamps, I don't see a compelling need to replace them. There is always the issue of stability, or, even worse, RF in a mod. However, if I was to order a new high end converter, I would ask, as I always do, that the chips be socketed for easy upgrade. That way, any component part can be replaced without dumping the whole thing in a landfill and starting over. At a minimum, I can reuse my toroidal power supply and chassis, and usually I can keep the circuit board, pots and so on. Better for the environment.

Alternatives to resocketing: you can buy a state of the art preamp card for $125, and simply bypass whatever you have in your gear http://www.audioupgrades.com/products/products_pre_card.htm

Not going to fit in the the DR 680, but I have a dozen or so preamps with cards, and you can retrofit a whole console with these.

So if you like the way the stock opamps sound, don't change them, buy a better microphone. But they do sound different.

Tests: theoretically, a faster OpAmp should have lower crossover point distortion. However, most people don't even test that. I can't ever remember seeing a test for this, so what are they testing? But, again, what would it matter what the test is, if you prefer the sound?

Vitaliy_Kiselev

I have a lot of gear that was designed so that you can just pop out the op amp and pop in another one. You can definitely hear the difference. I'm not saying one sounds better than the other, they just sound different. Some of them are clearer, some are warmer, some capture fast moving transients better.

Did you make any measurement? Double blind tests?

As I also hear difference between many things. If I see and know about it.

That way, any component part can be replaced without dumping the whole thing in a landfill and starting over.

And all else will live much longer? As I see zero logic here, because plenty of capacitors most probably will die much faster. Or you also put them all on sockets? :-)

I think the whole "scientific" thing would be like choosing a video camera purely based on the DxO mark. Why would you do that?

I see huge logic flaw here. op amp can and must be chosen according to specifications and actual measurements.

trevmar

"I think it is whole point to detail problems if you see them and have scientific and measurable proof."

Vitaliy, the reason "I don't have time to even begin to detail the mistakes" is that the science I have accumulated is not going to be appreciated by somebody who has not worked in audio design as a professional. I gave three examples of MAJOR parameters which were not canvassed in the blog, indeed are poorly understood these days "Intermodulation distortion," "Transient Intermodulation distortion," the ear's preference for even harmonics over odd". Measuring the IM shows class AB crossover distortion pretty clearly. Transient IM shows poor power conservation in many class AB op-amps (and discrete designs).

Sorry I don't have anything better than the PDF, the Internet didn't exist in 1979. Nor did scanners, or PDF files, for that matter. Much of this early knowledge has vanished into the bigger library collections. Maybe some day I will have the time to dig it out... And that was the point of my post. The old knowledge is dying out... Much has been forgotten over the decades since the NE5532 was designed... I did write up my experiences designing with today's Class D amplifiers, however, maybe somebody will work through its detail one day:

http://trevormarshall.com/class-d-tutorial/

DrDave

Re: measurements and double blind tests: yes, did double blind tests. We test all our gear. And we sell the stuff that fails. Tossed out the Neumann 140s. Didn't make the cut.

Caps croaking: I have stuff that's 30 years old, the caps are fine, but they are super high quality caps. But the stuff is designed so it is also easy to swap out the caps as well, which is typical. I think the power supply would go before the caps, but all the stuff still looks solid, and I can swap out the op amps for a few dollars--but I didn't, because the new ones are only very slightly better, and I worry about circuit stability.

Discrete opamp--it is a special sound, when done right. But most of my gear uses LM, LT etc.

Measuring: none of the tests you will see online test for zero cross distortion, but they do test for noise. Since the LM or LT parts run about $3 a chip, it is a total no brainer to take the 3dB better chip for $3. I mean, 3$ is a cup of coffee, why use a cheaper cheap that is noisier (the 5532) but then again, the noise is really low, so why swap it out if it works?

However, sound color is important, just as it is in microphones, just as it is in video. I would not buy a video cam on specs. I would not buy an op amp on specs. I would not buy a microphone and especially I would not buy a set of cans on specs.

Different opamps have different color, just like cams.

And speaking of double blind tests, when Bloom posted his results, people couldn't tell one camera from another. And that was single blind.

I say this because if you are going to use the blind testing standard, there is no reason to upgrade video cams. Why have a double standard?

But there are, presumably, more reasons than tests to upgrade. I will be buying the first solid 4K cam that goes on the market that has decent lowlight, because I really want the 4K for post.

And yet, I know, if the truth be known, I could probably not tell the difference from the new 4K cams and the Samsung Note 3 Android phone. I'm that bad at blind tests, and I admit it because why buy something you don't really need?

Vitaliy_Kiselev

And speaking of double blind tests, when Bloom posted his results, people couldn't tell one camera from another. And that was single blind.

May be it tells more about Bloom, compression and may be something about people? :-) I mean, it is not blind test fault.

Add to this that you constantly turn things thing into cameras :-) Problem is - vision and sound play different roles in our perception and they are differently processed and affected by our brain state.

I say this because if you are going to use the blind testing standard, there is no reason to upgrade video cams. Why have a double standard?

Because it is scientifically proven way to test audio.

Vitaliy_Kiselev

indeed are poorly understood these days "Intermodulation distortion," "Transient Intermodulation distortion," the ear's preference for even harmonics over odd".

Ok. Can you elaborate on performance of each of this parameters? Intermodulation distortion is not forgotten, even on audiophiles forums :-) As for even harmonics - concept is very popular now with plenty of valve amplifiers available, being one of their main push points.

Thanks for Class D link. What do you think about Tripath and B&O based amplifiers?

paulhouston

Similar horrible truth about audio interconnect cables. I have known audiophiles who swear by the bible that a $200 Monster cable sounds "vastly superior" to a $5 no-name coax cable. I have done many measurements/tests including intermods and harmonic distortions, and could not see any difference whatsoever. While not an audiophile, I have very sensitive ears, yet cannot hear any difference.

Yet the same people are happy with Zoom audio recorders as soon as they came out, and use them as the audio capture for the camcorders. To my ears, the early models of Zoom (e.g. H2, H4) sounded horrible: noisy, high distortions.

My conclusion? The great majority of the audiophiles are those who have pretty average (or even bad) ears, but who are susceptible to misleading or sexy advertising.

Vitaliy_Kiselev

Yet the same people are happy with Zoom audio recorders as soon as they came out, and use them as the audio capture for the camcorders. To my ears, the early models of Zoom (e.g. H2, H4) sounded horrible: noisy, high distortions.

Portable recorders are tiny niche, with about 90% going to home and small groups recordings usages.

But headphone amplifiers lately become big market with all set of audiophile myths and number of gurus. It is headphone amplifiers who are recipients of most of this opamps.

trevmar

Vitaliy, I test all the equipment I buy before I use it. Here is a distortion spectrum I took when I bought a Zoom H2 back in 2007. It is not bad, -51dB maximum distortion at an input level of -6dB.

I test microphones for overload using my sound level meter. Everything has to work well. And that is the problem. "Well" can only be defined by personal experience.

pundit

How about a $3,000 IEC power lead that will transform your HI-FI system?!

Well for $3,000 it must sound better... Mustn't it?

Okay so it transforms your bank balance instead... makes it smaller! ;)

http://sound.westhost.com/cables-p4.htm

DrDave

I'm happy to test audio scientifically; I just wouldn't buy audio gear based on the scientific test. And I understand that cameras and audio gear are different, but I think it is illogical to buy audio gear based on science and video gear based on "look"

Having said that, there really is very little scientific testing of audio gear. What we have instead is people using widely available software packages and just plugging their gear into it. This is absolutely not science, this is "fun with gear". So there is nothing wrong with this, and a "straight wire" approach, where you loop the audio signal back and measure the noise, is interesting. But it isn't Scientific.

In order for to follow the scientific method, you need to set controls, set baselines, and run full tests that are repeatable. We don't see this.

In fact, one "science" website tested the FR2LE and published completely different results from two different tests.

There are no baselines or control data, and a lot of the tests are missing data, like zero cross distortion. If you are missing tests, then there is no complete picture.

In the case of op omps, I can't see using a cheap part that that tests worse and sounds worse using the non scientific method used in a lot of these tests, if it is a $3 part. However, that's a personal choice. I tested them myself, and I heard a difference in the sound. That's good enough for me.

There was a famous post on Headfi where one guy said the high end gear didn't sound better than his computer audio output. He got a lot of flac for it. He was railed upon. But the fact is, I have one or two computers that have really good, super good audio jacks. I also have some that are terrible.

The GH1 tests better, scientifically, than the GH2. In every category. http://www.dxomark.com/Cameras/Compare/Side-by-side/Panasonic-Lumix-DMC-GH3-versus-Panasonic-Lumix-DMC-GH2-versus-Panasonic-Lumix-DMC-GH1___842_677_630

However, I sold my GH1 and purchased a GH2. So basically, what this shows is that the science is only good up to a point.

paulhouston

"The GH1 tests better, scientifically, than the GH2. In every category"

You are siting static image tests, without taking into account the processing of the static images into movies, a visual illusion.

Vitaliy_Kiselev

However, I sold my GH1 and purchased a GH2. So basically, what this shows is that the science is only good up to a point

I think main point that it shows that you tricked people :-) First going from op-amp measurements to cameras, after this telling that (tsss! secret!) that normal audio tests does not exist with basis being that you know some bad ones (and it is just logic flaw). And concluding that your camera purchase is not based on DXOmark.

Thing is - all your points are present in this article. Op-amps play their specific role and only way to do it is proper design and measurement of result (that every manufacturer is doing). As for more costly chips and difference - article on the link has perfect explanation for all this.

thepalalias

I've never listened to one of these, so I'd be curious on your guys thoughts on it.

http://www.ebay.co.uk/itm/141118957752

I have no expertise in op amps at all and I'm only just starting to lean into a dedicated headphone amp.

Vitaliy_Kiselev

@thepalalias

We have topic about HP amps. :-)

thepalalias

@Vitaliy_Kiselev I was staring at that for like 20 seconds before I realized "HP" stood for headphones. Sorry, it's probably always going to be Hewlett-Packard or "hit points" or "health points" in my mind. :)

Vitaliy_Kiselev

High-end audio was nearly non-existent in the 1970s short of a few companies like McIntosh and even those marketed their gear around objective criteria. If anyone tried to sell a $2000 power cord in 1980 they would have been laughed out of business but now there are dozens of companies selling them. The wine industry has followed a very similar path. In 1980 people tended to buy wine they thought tasted good. But, courtesy of decades of clever marketing, wine has been made out to be much more complex and important. An entire industry in the USA has grown up around wineries, wine tourism, wine bars, tastings, pairings, flights, expert reviews, etc. Consumers have been taught to doubt their own ability to judge wine and instead trust expert wine ratings with their point scores and elaborate tasting notes. And, not surprisingly, the experts tend to rate more expensive wines much higher. It’s scary how similar it is to high-end audio. Compare “the Warped Vine Cabernet was leathery with hints of green pollen” to “the UberDAC had a congested sense of pace and tarnished rhythms”. Check out the books by Robin Goldstein, Mike Veseth, Jonathan Nossiter, and the documentary Mondovino.

http://nwavguy.blogspot.ru/2012/04/what-we-hear.html

Vitaliy_Kiselev

DrDave

@Vitaliy, I sure hope I have not tricked anyone; I do my own research, so I can stand behind my results.

I will simply point out a few flaws in the opamp tests, and you can reach your own conclusions. Maybe I'm wrong and those test were perfectly done, certainly a possibility.

Scientific methodology is not a hard and fast fact. There are different ways to do tests. This is just my opinion.

First of all, they cherry picked the tests. That is, they did not test a number of crucial items like zero cross distortion. Why didn't they test that? I really don't know, but I suspect, and again, this is just conjecture, that they didn't build the experiment from scratch but instead used off-the-shelf software, which of course has no controls built in. However, I didn't see why they tested some things and not others. Do I care? No. I only care what it sounds like.

Second, there are no controls. Where are the bias controls? No controls, no science. It's a simple as that. I didn't invent the scientific method. Where are the standard deviation figures?

Lastly, they did find that the more "expensive" chips, and I put that in quotes because $3 is not expensive, are less noisy. Now, you can argue that less noisy is not important, but I personally would probably go for the less noisy one than the more noisy one, especially if my own tests show that the less noisy one sounds better. But suppose the noisy one sounded better? Well, then you have to choose, and in this case that 3dB isn't going to make that much difference anyway.

But here's the kicker--I buy the one that sounds the best. Well, I buy all of them and sell the ones I don't like. So my Sennheiser MKH 40 has a self dB noise of 10dB. The Neumann TLM 103 I tested has a self noise of of 7, 3dB better. I use the Sennheiser as my go-to mic. Now maybe the reason I didn't like the sound of the Neumann (which is certainly an OK mic, BTW) was the IC. The IC is the cheap chip they put in to cut down on the labor costs. Who knows? Well, I know. I took the capsule out of the microphone, and I had a discrete preamp built for it, and tested it again. Sounded much better (though not as good as the Sennheiser). And, it was also slightly noisier. That noise reduction came at a price, and the price was the sound quality. Just like in cameras. However, in the opamp, the noise reduction did not come at a price. It was a better design. You can take my word for it, or you can try it yourself. It is an expensive experiment, I can tell you that. So why would I do that? Because I had to know, is it the chip, or is it the capsule? Turns out it is the chip, in this case. Maybe I'm wrong, but it is my test, my reality. I can live with that.

So basically, I simply would not buy a mic, a chip, an opamp etc based on the test. That's not tricking anyone; that's the way I work. And I do not know a single audio engineer who would either. I've met people who swear by specs, but I'm not one of them. Similarly there is no way I would by a solid silver speaker cable. And yet, people do, and they swear they sound better. Are they delusional? Or do they hear better than me. I have no idea.

Now it could be that you are right and it is unfair to compare it to tests of cameras. That seems like a reasonable analogy to me, but I'm not an expert on camera sensors. So I can't say. I can't say if DxO methodology is good or not.

But I wouldn't buy a camera based on the specs, even though I'm not an expert. I still have to live with whatever knowledge I have and work with it--that's all I have. And there are plenty of people on this site who know more than me.

PS Re the above video--Poppy is one of smartest people on the planet.

Vitaliy_Kiselev

So basically, I simply would not buy a mic, a chip, an opamp etc based on the test. That's not tricking anyone; that's the way I work. And I do not know a single audio engineer who would either. I've met people who swear by specs, but I'm not one of them.

I got your position and understand it.

But, please understand mine. P-V will never ever will be place where "I feel so", "this is my subjective vision", "my ears told me that" is prized approach considering tech. We have enough of that around the web. First it must be measurements, if possible and objective things. Sometimes it can be hard.

About measurements. I see nothing badly wrong with them. If you know missing measurements or missed calculations, please reference were we can see tests made "properly".

Like one you referenced below:

Transient Intermodulation Distortion. TID (aka TIM) was proposed by Matti Otala in 1972, and the basic concept is 100% true. Unfortunately for the proponents of TIM/TID, it doesn't actually happen with real music in any reasonably competent amplifier (which is almost all modern amps, including IC types). Many have tried to demonstrate its existence with programme material, but to my knowledge no-one has ever managed to succeed. The information supplied in Wikipedia [4] is untrue - no known amplifier shows the problem with normal programme material

Crossover Distortion - A form of distortion caused by the power output devices in a push-pull amplifier operating in Class-AB. This occurs in valve and solid state designs, and is caused by one device switching off as the other takes over for its half of the waveform. There are some designs that claim to eliminate this distortion by never turning off the power devices, but in reality, only Class-A amplifiers have zero crossover distortion. This is generally measured as a part of the THD of an amplifier, and becomes worse as power is reduced from the maximum.

I also think that you understand how not firm is op-amps switching and preferences. And it is main reason that in each and every message you turn talks more to the mikes and cameras. :-)

Similarly there is no way I would by a solid silver speaker cable. And yet, people do, and they swear they sound better. Are they delusional? Or do they hear better than me. I have no idea.

They are delusional.

trevmar

High-end audio was nearly non-existent in the 1970s short of a few companies like McIntosh and even those marketed their gear around objective criteria .

What a silly statement. Analog audio technology was pretty well fleshed out by the early '70s and by the late '70s academics like myself were exploring the limits of Class D and Class E digital amplification. Nakamichi is one analog brand that excelled - measurably better than than McIntosh ever was - I still use a Nakamichi amp as my TV audio power amp, I forget how many decades old it is. Early '70s saw the introduction of delta-modulation and logarithmic PCM signal processing - which are still used as the basis for today's computer audio technologies. Celestion speakers from the 1970s (used in the Marshall guitar amps) are the speakers most desired by many (if not most) of today's guitarists.

I disagree that any conclusions at all can be drawn about what happens with 'real music.' As somebody who has designed power amps (voice and guitar) for rock musicians (including Bon Scott) and also classical HiFi rigs, I know that none of my amps with bad IM and TIM ever sounded good. Mostly these are not subtle defects, either.

I agree 100% with the craziness about silver cables, etc - that was a trend which came along after the basic technology was fully developed. Early 1980s, if I remember correctly. While I also agree that swapping out op-amps for a (circa 1980) NE5532 doesn't make a lot of sense, some of the newer circuits, particularly from Analog Devices, do have more linear circuitry and wider bandwidth, and are usually what I choose when I need an audio op-amp. Fundamentally I am a discrete-component guy, however. The op-amps have buckets of gain trying to overcome their non-linearity with negative feedback. Discrete component audio design generally relies on fundamentally linear circuitry, with only a small amount of negative feedback.

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