@asctim I can't seem to convince that guy that what he's saying about me is wrong. 🙄
@ricevs This is not a discovery. Those that have listened, have known this since audio reproduction and measureing equipment were invented. Most things that make a sonic difference cannot be measured.......plain and simple.
This was true back sometime in the 1980s. But measurement tech like nearly all other technologies has improved quite a lot in the last 30-35 years :)
But many people don't realize that, and worse yet, wouldn't understand the import of the measurements if they saw them- and quite often, they are not published. So the myth (as purported above) continues.
These days there is a direct line between what we can hear and what we can measure. The tricky bit might be understanding what to measure...
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You just stated above that any modern op amp has no sound (will not change the sound).
@ricevs
The above statement is false. Here is what I actually said:
Not to put too fine a point on it, but when you can change an opamp (if its modern, hi performance) and hear a change (other than noise floor), one of two things is happening: 1) confirmation bias, or 2) the circuit has a design flaw.
That isn't me saying 'any modern opamp has no sound'!
What I am saying is that if you know how to design with opamps, and if you compare high performance opamps, then you will not hear any difference other than perhaps the noise floor.
I know there are companies that make a living selling opamps based on them having a 'sound'. But any engineer finds that sort of thing to be a facepalm event. It means either the opamp is poor performance compared to what is readily available (and probably for a lot less money) or the circuit in which it is used is poorly designed, or both.
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Wow, you just stated that all modern op amps are perfect.
Uh, no, I didn't. This sort of comment on your part is known as a Strawman; its a logical fallacy and false by definition.
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People all over the world have changed those op amps and get different sound.....You, however claim that in a low gain circuit that all op amps have no sound. You are again a minority of one here.....thousands of audiophiles and manufacturers would disagree.
Not to put too fine a point on it, but when you can change an opamp (if its modern, hi performance) and hear a change (other than noise floor), one of two things is happening: 1) confirmation bias, or 2) the circuit has a design flaw.
Opamps have seen a lot of evolution over the last 75 years; guitar stomp pedals and synthesizers from long ago won't sound right if you install newer hi performance ICs instead of the original types. This is because older opamps indeed have a 'sound'. Modern ones do too if you don't use them correctly.
Put another way, the statement in the quote above is false; I never said that 'all opamps have no sound'. Clearly you don't read my posts or you would know that.
Anyone can open a class D amp and change how it sounds! Quite often their changes result in greater noise.
From your posts it appears to me as if you think you know more than other designers. So its curious that you haven't designed a module of your own long ago!
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NAD’s Director of Technology, Greg Stidsen, had this to say: “Like all amplifier classes, there are advantages and disadvantages to class-D. What is attractive about class-D is its relative efficiency and freedom from the vagaries of parts quality. In a linear amplifier such as class-A or class-AB, parts-matching and very close tolerances are required to get the best results, and even then, there is a limit to performance since the linearity of semiconductors varies considerably with temperature.
“With class-D, it’s more the quality of the mathematics and engineering that determines the performance,” Greg said. “Another way of saying this is that in a linear amplifier the design is fairly simple, but the execution is critical; in a switching amplifier, the design is very difficult, but the execution is straightforward.”
https://pmamagazine.org/is-class-d-amplification-now-better-than-class-a-b-and-class-a/
(Emphasis added)
Greg put this pretty well.
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The only way to know if a single component (or several) changes the sound and or measurement is to use the same amp and just change the parts. Then you will actually KNOW something.
This statement contradicts this one:
I did not say it changed the measurements....
I have found over the years that when someone is willing to contradict themselves in an argument, its never about the truth of the matter; its only about trying to make the other person wrong.
This makes a noticeable sonic improvement......and no, I bet you cannot measure it.
(emphasis added)
Despite the obvious syntax error, the above statement suggests that no attempt was made to measure any of the changes introduced. The reason you would want to do measurements after changing anything in a class D circuit is noise and parasitics can show up, which can interfere with other equipment, for example an FM tuner or digital equipment sitting nearby. Bruno, the designer of the Purifi and Hypex modules, is very emphatic about this in his papers.
@lanx0003 BTW, if anyone tells you they have 6N (6 Nines, IOW 99.9999% copper) copper wire, if you are in their presence it might be sensible to turn and run as hard as you can. 6Ns copper is a myth; it does not exist. Wire manufacturers just laugh if you suggest this sort of thing to them. What is real is OFC (Oxygen Free Copper), which was not developed for audiophile applications (see the link).
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I have NEVER in my entire life heard of any high end audio designer, engineer, manufacturer say this
Hm. Not been around, apparently.
The only way to know if a single component (or several) changes the sound and or measurement is to use the same amp and just change the parts.
Wait- what? So if you change parts it does change the measurements?
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Did you not read what I said? I said the amps will all measure the same.....this is absolutely true. While it is true that when changing parts the distortion changes....because all noise and veils are distortion. However, you CANNOT measure a change in measured distortion when changing passive parts.
@ricevs Oh I read what you said. But it was false, as is the above statement. You certainly can measure a change in distortion when passive parts are replaced! The idea that this isn't so is laughable.
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Yes, the amount of distortion and its spectrum has some correlation to sound. However, it is not the major or only thing that makes and amp SOUND the way it does. You can give me 3 pairs of Atmasphere amps and I will change some of the parts in one to really bad sounding parts.....leave one of them stock and in the 3rd one I will change a bunch of parts and execution that I know will make the sound better. They will still all measure the same. Ralph or anyone would be able to pick them apart..........even on a double blind test.
When you change parts, you change the distortion so the sound changes. This is easily measured and correlated to what we hear. So they would not measure the same. Distortion is literally the sonic signature of any amplifier.
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Most agree that the 2nd harmonic is innocuous to the human ear; the real issue here is are the 2nd and 3rd able to mask higher ordered harmonics. I've heard the argument before that if they are 90dB down you aren't going to here them, which I think is false due to the fact that the ear uses higher ordered harmonics to sense sound pressure and it has over a 120dB range.
But if the 2nd or 3rd is masking them, then you have a 'tube amp' signature. The lower the distortion overall though, the more transparent the amp becomes.
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@lanx0003 The differences you hear in the sound of amps, if FR isn't an issue (which most of the time it isn't) is the difference in distortion of whatever amps are being compared.
There are three things that define those differences. What frequency, if any, that distortion rises (IMO/IME this aspect of amplifier distortion is the most important), the distortion spectra and finally how much distortion. There's no filter that would make a solid state amp sound like tubes; just the distortion signature. So if a class D has the same distortion signature as a good tube amp, it will sound like a good tube amp simply on that account.
This is because our ears use harmonics to identify any sound. So you can see that if an amp is to sound musical, its distortion signature must be as innocuous as possible. To that end, the 2nd or 3rd must be significantly higher amplitude than succeeding orders, so as to mask them. That is literally what has kept tubes in business these last 60 years.
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@lanx0003
I was looking at a different article. In this one we see a dominant 3rd (my memory playing up; I still seem to recall seeing a dominant 2nd) which is treated by the ear in much the same way as the second and is the only odd ordered harmonic for which this is so.
A dominant 3rd suggests cubic non-linearity; if so the circuit is inherently lower distortion than when a 2nd is dominant (which suggests a quadratic non-linearity). Our OTLs, being fully differential and balanced, have a dominant 3rd.
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@lanx0003 Sure! Just look at the harmonic spectra of the Purifi module. You'll see a dominant second.
Keep in mind that in a class D amp, the things that cause traditional solid state amps to sound harsh and bright might not exist. For example, in our class D the primary non-linearity is caused by the deadtime used in the output section (something that all class D amps have). In our circuit this results in lower ordered harmonics.
When feedback is applied to most tube and solid state A or AB designs, it is traditionally applied to a non-linear input to the amp (the cathode of an input tube or base/gate of a differential pair at the input of a solid state amp). The feedback signal is thus distorted and so does not do its job properly. This causes higher ordered harmonics and IMD. This has been documented by both Norman Crowhurst (technical writer for Sams publications) and 20 years later by Peter Baxandall.
In most self-oscillating class D amps this technique is not used. So they often lack the higher ordered harmonic generation common to 99% of traditional solid state designs.
Since the ear uses harmonics to tell the difference between sounds, you can see that class D amps are capable of very different distortion as opposed to traditional solid state. So I don't see it as counter-intuitive that a class D amp can have a lot more in common with the sound of a tube amp than regular solid state amps.
Of course, class D designs vary a lot in their sound so YMMV. IME they can vary more than the sound of tube amps, which can very quite a lot! The point here is don't write off class D because you may have heard one that sucked. As with class A or AB, the sound quality is a function of design and execution rather than the class of operation.
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I added a THD (%) scale, which corresponds to the dB scale, into the graph for comparing more affordable NAD C268 ($1k) and the Bel Canto S300iu ($2.5k) with the Fosi V3. As shown, the NAD C268 is comparable to the Fosi V3, but the Bel Canto is far inferior. Again, measurements do not mean everything, but the THD measure does give an indication of the sound clarity. I just provided you with the data in one place for your convenience, and it is your discretion how you interpret the data.
@lanx0003 The THD really doesn't tell you how musical an amp might be. A better indication is distortion vs frequency. If it rises at too low a frequency, higher ordered harmonics might be unmasked and so contribute to brightness and harshness. Ideally (and a number of class D amps can do this) distortion vs frequency should be a ruler flat line across the audio band.
Zero feedback tube amps (like most SETs) have always been able to do this. But a good class D can do it better, with lower distortion (which obscures detail).
Once DvsF is sorted, the next hurdle is the actual distortion spectra. Ideally a 2nd harmonic should be the most powerful, followed by the 3rd with succeeding harmonics quite low in comparison. In this way the lower orders can mask the presence of the higher orders, allowing the amp to be as smooth as possible. Again, some class D circuits are very good at this, challenging SETs and other tube amps on their own turf.
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