You are technically adept at deciding what kind of amp you want, so I don't think you will struggle to identify your type of amp. In the proposal, you will be able to see the distortion, noise and other figures - but beyond a certain point, some of these numbers i.a.o. will not be rewarded for excessive design/engineering focus in the ranking, that's the only difference.
Zero feedback amplifier is a technical nonsense. First, it is impossible, there will always be some kind of feedback, even if someone cannot see it. For some strange reason, audiophiles and laymen audience have reduced the term ”feedback” only to global negative feedback from output to input. One can make a “zero feedback amplifier” then from a gain stage and a power buffer, there will be no GNFB, but output impedance will be easily as low as 0.05 ohm. So, let us not speak about zero feedback amplifiers.
Perhaps, but it will "fool" other who aren't because the will not be able to assess the ranking system. I don't even need a ranking system. Ranking systems are for persons who want good clinical performance but don't have the knowledge to do the assessment.
I'll go for a car analogy 😉 ...
- I want a fast accelerating car! Yes, we have this with a nice carburettor that is really fast - it ranks a 12 - OK, what more? Perhaps this with injection - it also as fast - ranks 11. Nice - how fast? The carb does it 9 and the injection in 8,7.. - But!!?? - Carburettors are nice and shouldn't be penalised. -Good day.
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I think nowadays is also no space for tube power amplifiers, for other reason than nostalgia only.
IMO, much of the reason for the wackiness in audio is that good amplifiers are perfect for all practical purposes. As a result, amplifiers are distinguished based on engineering feats ("THD Wars", "Watts Wars"), intangibles (BJTs/MOSFETs, feedback), appearance, and/or intentionally less-than-perfect performance (tubes). The motivation is "differentiation". This appears to work at least for smaller manufacturers.
Ed
Ed
To say that an audio amplifier should be a wire with gain, is itself a subjective judgement. The fact is we are humans talking about evaluating devices that are intended to be used for the enjoyment of humans. There is no way to completely eliminate human factors in this effort.
I can't seem to generate a decent .pdf file - its all chopped up and the pages are screwed up.
How/why would 'sales' have more merit as a basis for technical requirements than sound quality assessments?
What's the point if the crux of the matter is outsourced? Also it seems ironic that what's good for amplifiers -- feedback, say -- is not so good for the committee, and 'sanity' (linearity) is not guaranteed by design, but is sort-of calibrated ahead of time on a "fingers crossed, let's hope we chose the right parameters!” basis.
The spreadsheet is too wide to fit on a page. You need to make it narrower and/or use a program that understands pagination. Word may be easiest. I like TeX but it has a learning curve.
Ed
I do not understand what you are trying say here. Can you explain what you mean
(What committee are you talking about?)
I have no experience with Google docs. Reformatting the contents of the spreadsheet into a printable document will require work in any program.
Ed
Needs some more work (copyediting and prettying) but here's a PDF of the first sheet from the doc. I'll look at the other sheets as I have time (second tussle with Covid in four months so I'm not leaving the house much til Thursday, but the kids and I have a lot of hot wheels to race...)
Hello, I'm digging up this thread a bit, which I find interesting.
I think there's a real need to identify the technical points and/or measurements that allow us to evaluate the objective quality of an amplifier.
In reality, at the moment, I don't think anyone is capable of truly determining the quality of an amplifier through measurement alone, but I think it's probably possible to do so, but it's much more technical than what is usually proposed.
Many points have been addressed (IMD, the THD spectrum rather than just its absolute value, noise too, etc.)
The severe limitation of measurements performed only on pure resistive loads...
I'm only an amateur, but from my personal experience (only with Class AB or Class A amplifiers)
I can highlight certain points that seem important to me for audio quality:
- The linearity and speed of the transistors, especially the output transistors on a Class AB amplifier.
- The quality of the power supply seems fundamental to me, and I don't seem to have seen any measurement capable of taking it into account. Thus, all the amplifiers with unregulated power supplies that I've tested were inferior to a fully regulated amplifier (perhaps due to ripple?), even Class A amplifiers.
- The quality of each passive component used can provide a small advantage in itself, which means that using only high-quality components ultimately results in a real gain.
I'm not talking about the intrinsic quality of the diagrams used; many are actually quite similar and fairly standard, at least for Class AB models.
Regarding THD, I completely agree that focusing on this criterion alone is foolish; in my experience, when you try to reduce it too much, you inevitably degrade other parameters. There's a compromise to be found for each diagram. It's a bit like digital photography with the pixel count war, or CPUs with the GHz war at one time...
I think there's a real need to identify the technical points and/or measurements that allow us to evaluate the objective quality of an amplifier.
In reality, at the moment, I don't think anyone is capable of truly determining the quality of an amplifier through measurement alone, but I think it's probably possible to do so, but it's much more technical than what is usually proposed.
Many points have been addressed (IMD, the THD spectrum rather than just its absolute value, noise too, etc.)
The severe limitation of measurements performed only on pure resistive loads...
I'm only an amateur, but from my personal experience (only with Class AB or Class A amplifiers)
I can highlight certain points that seem important to me for audio quality:
- The linearity and speed of the transistors, especially the output transistors on a Class AB amplifier.
- The quality of the power supply seems fundamental to me, and I don't seem to have seen any measurement capable of taking it into account. Thus, all the amplifiers with unregulated power supplies that I've tested were inferior to a fully regulated amplifier (perhaps due to ripple?), even Class A amplifiers.
- The quality of each passive component used can provide a small advantage in itself, which means that using only high-quality components ultimately results in a real gain.
I'm not talking about the intrinsic quality of the diagrams used; many are actually quite similar and fairly standard, at least for Class AB models.
Regarding THD, I completely agree that focusing on this criterion alone is foolish; in my experience, when you try to reduce it too much, you inevitably degrade other parameters. There's a compromise to be found for each diagram. It's a bit like digital photography with the pixel count war, or CPUs with the GHz war at one time...
This was a attempt to try to put some sense into assessing amplifier performance, no matter what the technology (class D, class AB, class A, tubes etc) given the vagaries of the human ear/brain system, outrageous claims made by manufacturers, some designers and sections of the hi-fi press, along with the seemingly intractable and interminable arguments between objectivists and subjectivists. AFOM, it was hoped, would lead to amplifier designs that addressed key parameters in a holistic way, leading the engineering effort to be put into all of the factors that make a good amp, and not just one parameter, as seems to be the case now with regard to distortion.
The whole thread descended into another endless argument between siloed opinions with little regard or appreciation of what AFOM was trying to achieve. I am of the opinion that the thread should be closed since it will achieve absolutely nothing but more noise.
The whole thread descended into another endless argument between siloed opinions with little regard or appreciation of what AFOM was trying to achieve. I am of the opinion that the thread should be closed since it will achieve absolutely nothing but more noise.
I don’t looking into performance number that much. The test equipment plays a big role of the results. The numbers are only comparable under the same testing equipments.
However, some parameters are still more important than others. Usually, I only look at two parameters, THD at 5W and Hum level. Less than -80dB THD should be a good indicator. As said, don’t worry about the actual figures. They are not comparable with different testing equipments.
Don’t over complicate the problem. The performance is determined by amp’s topology. For example, EF2 output stage with 40dB feedback, you will get -80dB THD. If you increase NFB by 10dB, the THD would improve by 10dB. That is simple. There would be variances by different transistors, but not by much. There is no miracle devices. Thus, I always read the schematic if possible.
However, some parameters are still more important than others. Usually, I only look at two parameters, THD at 5W and Hum level. Less than -80dB THD should be a good indicator. As said, don’t worry about the actual figures. They are not comparable with different testing equipments.
Don’t over complicate the problem. The performance is determined by amp’s topology. For example, EF2 output stage with 40dB feedback, you will get -80dB THD. If you increase NFB by 10dB, the THD would improve by 10dB. That is simple. There would be variances by different transistors, but not by much. There is no miracle devices. Thus, I always read the schematic if possible.