“TO-92 transistors are not bad”, because often you can stick just about anything in there and have it still work. Unless they are the wrong polarity, which has been known to happen.
Also, fake “500 watt” amp boards running off +/-30 volt power supplies will work just fine with fake C5200 output transistors. The number of watts is often just as fake as the parts.
Also, fake “500 watt” amp boards running off +/-30 volt power supplies will work just fine with fake C5200 output transistors. The number of watts is often just as fake as the parts.
The tube amp and efficient (read: large) speakers always cost more in RENT for the cubic footage they occupy (and insurance in case stolen). That part of the equation is usually more expensive than the electricity cost.
Intent itself to make A-Class amplifier implies high quality, without compromises....Is there any other choice in terms of price / quality ratio?
TO-92 transistors are not bad
Speaking about price/quality trade-offs is pointless when quality transistors comprise just a small fraction of overall costs. For good DIY amplifier one must be prepared to pay much more than for commercially available units. There is no way to avoid higher costs and have high quality at the same time. This is really either or, exclusive set of decision routes.
This amplifier will sound as much as it costs, perhaps worse. Elsewhere we may observe a massive fireworks of fake transistors that can not sustain any serious test. They just blow, like pop-corn.
Anyone may make own decisions according to desired quality and availability of resources.
That's what I wanted to say.
No pasaran
even if I have to go illegal I will not give up class A , I doubt that class D will ever be equal to class A
Actually good AB and D is various orders of magnitude measurably better than class A. The good news is that computational power is becoming cheaper by the day so you will be able to add the distortion you miss in the digital domain. So it will sound like Class A, but it will use less power!
Maybe class A has poorer measurements, but sound is something else.
Almost two decades ago I made my first amplifier in the class A and as I worked in a hi-fi shop I brought it up for comparison, it easily beat two amps in the 4000-5000 $ price range. The small Pass ZEN did not have the power like these two in the class B and AB , but it beat them with sound quality. The amp was a couple of days in the shop and everyone was surprised by the sound quality.
It was the best confirmation in the superiority of class A and since then I have only had diy class A.
Almost two decades ago I made my first amplifier in the class A and as I worked in a hi-fi shop I brought it up for comparison, it easily beat two amps in the 4000-5000 $ price range. The small Pass ZEN did not have the power like these two in the class B and AB , but it beat them with sound quality. The amp was a couple of days in the shop and everyone was surprised by the sound quality.
It was the best confirmation in the superiority of class A and since then I have only had diy class A.
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But that experience of yours was twenty years ago.
A lot of water has passed under the bridge since then in class D.
I use a Bheringher NX3000D to exclusively power two subwoofers, but I tested them in their full frequency range with my Troels DTQWTII speakers and was really surprised, great sounding, far outperforming the renowned vintage AB class NAD 3020.
I think class A is fine for high sensitivity cabinets, (+/- 95 DB / w / m) but in that case, I prefer a 300B tube.
I discard a 2A3, because for them you need extra high sensitivity, more than 100 DB.
Heard an ACCUPHASE E-650 Class A amplifier with Proac 125 cabinets. Nothing special. But it's just my opinion.
A lot of water has passed under the bridge since then in class D.
I use a Bheringher NX3000D to exclusively power two subwoofers, but I tested them in their full frequency range with my Troels DTQWTII speakers and was really surprised, great sounding, far outperforming the renowned vintage AB class NAD 3020.
I think class A is fine for high sensitivity cabinets, (+/- 95 DB / w / m) but in that case, I prefer a 300B tube.
I discard a 2A3, because for them you need extra high sensitivity, more than 100 DB.
Heard an ACCUPHASE E-650 Class A amplifier with Proac 125 cabinets. Nothing special. But it's just my opinion.
If you are saying that good AB - and particularly D - measure much better than Class A ... then I agree with you.
But grunf, below, has hit the nail on the head!
I recently finished building two Class A amps (Hugh Dean's "Alpha Nirvana" - there's a thread in this section). Unfortunately, with a bias current of 3a, they do have a high heat output - hence I will need to use my Class AB amps in the summer months.
There is a biiiig difference in the sonic pleasure delivered by the Class A amps, compared to the Class AB. In particular - a much deeper soundstage!
Andy
Those skilled in mathematics, especially mathematical modeling, may grasp limitations of:
(1) square wave response and
(2) THD measurements
because they both rely on Fourier finding that:
some functions could be written as an infinite sum of harmonics.
This finding is absolutely correct but it is utterly wrong to apply it directly, without further considerations, to any kind of amplifier because complexity of the actual physical system is simply too large to be represented by such a simple model. (Yes, Fourier transform is complex, yet too simple.)
In simple words: THD and square wave response may be used to distinguish among bad and good amplifier but will never be capable distinguishing among “very good” and “even better” amplifier. Simply, these methods have too severe limitations to perform such a task. Period.
I usually do not listen to my amplifiers before they pass all tests. The final test is listening.
There are other good amplifiers but A-Class rules them all, if you are prepared to accept some co-lateral damage, such as large heat sinks and expensive power supplies.
But if you want high sound quality along with high power output, then the best way is to adopt the approach suggested by Ian Finch previously in this conversation. Here is the quote:
(1) square wave response and
(2) THD measurements
because they both rely on Fourier finding that:
some functions could be written as an infinite sum of harmonics.
This finding is absolutely correct but it is utterly wrong to apply it directly, without further considerations, to any kind of amplifier because complexity of the actual physical system is simply too large to be represented by such a simple model. (Yes, Fourier transform is complex, yet too simple.)
In simple words: THD and square wave response may be used to distinguish among bad and good amplifier but will never be capable distinguishing among “very good” and “even better” amplifier. Simply, these methods have too severe limitations to perform such a task. Period.
I usually do not listen to my amplifiers before they pass all tests. The final test is listening.
There are other good amplifiers but A-Class rules them all, if you are prepared to accept some co-lateral damage, such as large heat sinks and expensive power supplies.
But if you want high sound quality along with high power output, then the best way is to adopt the approach suggested by Ian Finch previously in this conversation. Here is the quote:
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You owe it to yourself to check what has been achieved in 20 years. You might be surprised.
Jan
This does not hold water. If I measure the weight of an item, that weight does not depend on the complexity of the item.
FFT simply tells you what a signal consists of. If you are concerned about the complexity of a signal, you can do a multitone test with 30 different simultaneous tones and look at the distortion, intermodulation and noise in the presence of signals, using FFT techniques. The actual complexity of the amp doesn't figure in that, ONLY how it treats a signal.
FFT doesn't tell you how something sounds. neither does 'class A' or '200W' tell you how something sounds. But FFT techniques can tell you how much an amp adds or subtracts from a clean signal, and we generally want that to be as low as possible. Of course, if you prefer warm, muddy sound, you don't want a clean amp! It's all about personal preference, there is no definition of 'best sound', it varies from person to person.
Jan
OK, Jan ... perhaps you can explain how FFT techniques will explain what is going on when 2 different amps produce the following results - using the same source and into the same pair of spkrs. The amps are:
1. a Purify 452 (I think the model is) stereo amp.
2. A pair of Audio Research 250SE tube monoblocs.
#2 produced a deep soundstage, from the plane of the spkrs to waaay back.
#1 had a flat soundstage.
This difference was easy to hear ... I'm curious to know what measurements would explain the difference we heard.
Andy
Note that I said "good" AB and D (and I would now add B). Low THD, IMD, and SID (slew rate induced distortion) also contribute to a more faithful signal - cheap (or old) AB and D amps lack in this respect, sometimes egregiously so.
Class A can also measure spectacularly well, and it is not even particularly expensive to achieve that, by the way.
But grunf, below, has hit the nail on the head!
I recently finished building two Class A amps (Hugh Dean's "Alpha Nirvana" - there's a thread in this section). Unfortunately, with a bias current of 3a, they do have a high heat output - hence I will need to use my Class AB amps in the summer months.
There is a biiiig difference in the sonic pleasure delivered by the Class A amps, compared to the Class AB. In particular - a much deeper soundstage!
And here I disagree. We are now talking about both subjective and sighted comparisons. This automatically invalidates any attempt to draw any qualitative evaluation from them. And if these Class A amps have moderate amount of distortion, esp second order (so they must be single ended, or have a single ended driver to a push pull stage), then they may sound subjectively more pleasing – I know this from experience – but it does not mean that they are "better'. One may like them more, of course.
There can be a lack of dynamics in AB amps that use simple feedback loops – it is not the feedback per se that is bad, but the simplistic approach to it, which can be detrimental to dynamics.
And there is the "scarrafone" effect: what one builds oneself always sound better ("scarrafone" means "cockroach" in the Italian dialect of Neaples. They have a saying "Ogne scarrafone è bell' a mamma soja" - which translated to "Each cockroach is a beauty in its mom's eyes"). My Class D amp (with a Neurochrome buffer) is of course the best sounding amplifier on the planet!
The Class A amps that I built have +/-22v DC rails - so not 'SE'.
My definition of "better" ... is that they deliver more sonic pleasure.
Haha - I like that ... and it is very true!
But in my case - the Class AB amps that I am using in summer ... were also built by me; so they are both 'scarrafones'.
Andy
The future for class D for critical listening is now. In fact, it has been that future for a few years now.
So they are balanced? push pull?
My definition of "better" ... is that they deliver more sonic pleasure.
Perfect.
[The scarrafone effect] Haha - I like that ... and it is very true!
But in my case - the Class AB amps that I am using in summer ... were also built by me; so they are both 'scarrafones'.
It may be that you are better at building Class A amps than AB amps ;-) In fact, getting the latter to work properly is not easy at all. You could try to use a trick used also by Cambridge Audio: add a bit of DC to the signal before the amplification and them remove it at the end (you can do that in a fixed way instead of using a DC servo at the end, since you know your gain). This should reduce the influence of crossover distortion on the signal by orders of magnitude.
But of course, my statement absolutely holds water and you can not view this complex phenomena in terms of simple weighting a kilo of potatoes. Just look at the complexity of events at the cross-over region (observe the difference: I am not talking about the "point", instead I use proper word "region"). There is a plethora of possible outcomes and functions representing the underlying phenomena are rather complex, or should I say "fuzzy". There are discontinuities, overlapping trends, functions aren't differentiable, function can abruptly drop to zero and suddenly emerge from nowhere. How that can be presented as an infinite sum of "harmonics"?
On the other hand a kilo of potatoes is in front of you, it doesn't move and you can read its weight correctly, as a simple value representing it's mass. By the way, are you sure that a kilo is really a kilo. It is much more complex. Consult Albert.
When you measure in "frequency domain", you in reality measure voltage as a function of time. The magic hidden inside your instrument uses an algorithm to present the measurement results as a function of frequency. But remember, the algorithm "assumes" that the input signal is a finite sum of harmonics. Is that true? Honestly.
Now, human reasoning tends to accept the measurements as scientifically correct beyond any doubt. I was actively involved in scientific measurements for decades and I perfectly understand that all circumstances and especially assumptions must be carefully evaluated during interpretation of the results. Remember, we are talking about values that are beyond human perception. Hence, we use instruments to extend our perception to the "invisible", in contrast to obvious variables like the weight of an object.
Furthermore, human mind rejects complexity and rather decides for simplicity of a single absolute parameter: THD.
Take all these THD measurements with a grain of salt. And think what is really happening behind the scene. Otherwise you will place fog and mirrors in front of your own reason.
No offense meant, whatsoever.
Cheers
No, they do not have a balanced topology - RCA inputs.
I am afraid I am no expert; I know they are 'Class A' (so the NPN and PNP Mosfets never turn off) - but whether this is defined as 'push pull' ... I have no idea.
Andy
I said I "built" both amps; what you are suggesting, seems to me to be part of the design stage?
I don't design - merely construct.
Andy
I don't know of any measurement that measures sound stage width in amplifiers. But the deeper question is: was this your personal impression, or was this concluded from a controlled test?
I'm sure as an experienced audio person, you are well aware of the impact of personal opinion and convictions upon audio perception.
Jan