Are class A amplifiers significantly harder to engineer, or they are
about the same but only bring some of the well-known things (heat) with
them simply because of class?
Also, how does efficiency of class-A amplifiers compare with other classes (ballpark figures)?
They are not harder to engineer. Its arguable that they are a bit easier, although you have to be more careful about heat issues and the power supply has to be able to support the output section being on all the time, something that you don't get with AB amps.
Of course class A is the least efficient of all classes of operation. The advantage is the output devices are often biased at the most linear portion of their curve. So if all goes well, they will make the least distortion.
My class H is the Carver Sunfire 600. Pretty sure it’s class H. She sounds great, pretty much unlimited power with that amp! Clean, open, great sound on all spectrums , bass, mids and treble are all superb!
I especially love both taps, and switch quite often, depending the music I listen to.
The tube sound tap, is great, makes my listening very enjoyable.
If you love the sound o your amps no matter where they rate in class, a, a/b, h, d.
Dear @inna : After all those posts you already know that class A not always sounds better.
Some of the posts said that depends of amps design and I add quality excecution to that design. I have this first hand experiences with Mark Levinson amplifiers:
its first amplifier named by them Reference ( and this is not a marketing name/model, when ML says that it's because it's a true reference and not MK like other products. ) were the model 20 pure class A monoblocks. Years latter they puts in the market the new class AB model 23 and things were that the 23 outperformed the Reference 20s.
ML inmediatly took the problem and fixed with a modification in the 20s and then born the new Reference 20.5 but even with that experience Levinson again puts a new class AB amp in the market that was the 23.5 and wonder what: again the 23.5 outperformed the 20.5s and Levinson had to fix it and did it through the Reference 20.6s.
I still own the 20.6 with some modifications by my self and a friend of mine and owned the 23 and 23.5.
What made Levinson in his pure class A Reference 20 and latter in the 20.5? , they don't touch the output whole design but made the changes ( twice ) at the input design at the input circuit boards and through those changes the 20.6 outperformed the 23.5. Even that the 23.5 was very good class AB amplifier.
Theshold had the class A SA-1 monobloks and at the same time Pass designed the class AB S500e. I listened both models several times and the class AB was a better performer.
Crossover distortion not always makes the difference for the better. Design and excecution quality level to that design is really what it counts, it does not really matters if class A or class AB.
Are class A amplifiers significantly harder to engineer, or they are about the same but only bring some of the well-known things (heat) with them simply because of class?
Also, how does efficiency of class-A amplifiers compare with other classes (ballpark figures)?
In solid state amps only a handful and in tube only a handful also they
are incredibly difficult to make and unreliable due to heat generation
because of the 10 percent efficiency. So most of the makers if not all
stopped making them.
This statement is false. We've been making class A amps for over 45 years. Reliability isn't an issue- that's an engineering problem, not something inherent in the class of operation. They are more efficient than 10% too- that's about a country mile off as the saying goes.
The lowest distortion amp in existence is class AB. The problem with this amp is it doesn’t have any low-order harmonics to help mask any inadequacies in upstream gear or the recording.
I like what ARCAM did with their AVR 850 with their class G technology. Great design. I would imagine the big concern would be the heat factor. AB is a good compromise.
For what it's worth, I have two Class A amps, a Reference Line Silver Signature (modded by Roger Modjeski, RIP) and a Plinius SA-103 (heavily modded by Vince Galbo Designs). Both put more than 100w into 8 ohms. I used to have Bryston 28B SST2, an AB amp that put 1000 watts into 8 ohms. I had all three amps at the same time, so I could easily compare them in my system, which includes PMC IB2i speakers (known to love Brystons). The class A amps sounded better by pretty much every parameter. The Brystons are long gone. What's more, the Plinius has a button you can press to switch the bias from AB to A. Class A sounds better, by no small margin. Again, FWIW.
Yes but take away blanket assumptions and there goes 80% of site content. Take away pure unsubstantiated blather and there'd be like three of us left all reading each other.
Basically you can say, all things being equal Class A sounds better, but all things are rarely equal are they? I can't see myself owning anything other than a Class A triode wired tube amp but my setup is optimized for that style of amp.
The history of audio shows that you cannot make blanket assumptions on any product based on theory: There are too many variables to make any conclusion that class A is always sounds better than class AB. The results are aways dependent on the synergy between the amp, speakers, and room.
Seems to me that everyone is addressing the question solely with regard to SS amps. Ask the same question about tube amps and I think it would be generally agreed that a pure class A SET will win out over a class A/AB push pull triode as long as they are matched to the right speakers.
Hear, Hear... jw944ts! I have, after almost 50 years in this wonderful hobby, ended up with "mostly" tube equipment, push pull A/B, with Martin Logan hybrids and auto formers (take it easy georgehifi, my preference, my system). Sounds great to me (and associates). My best friend(s) have older Morrison mono class A SS amps, with Morrison (new model) speakers. Sounds great to us. Our other friend, has Mark Levinson 300w amp and some European (German) stand mounts. Sounds Great. I think the point here is that, yes, there are general "rule of thumb" guidelines but.... there are no absolutes (class A is superior.... etc). Way too many variables and always an exception to "the rule". My take on all this... that it is a valuable endeavour to mix and match, swap equipment in and out, socialize and listen to music (and gear). As jw said...ENJOY....
Also not true. AB can have vanishingly low distortion. Compare for instance Pass' class A designs. He deliberately designs for euphonic distortion. He does not make absolutely low distortion amps nor does he wish to. It's exactly his house sound.
So, neither sound nor measurements are better universally by class. Class D for instance can best many Class A for distortion and low output impedance. Not always though.
What is true is that the crossover distortion vanishes with Class A. Sound quality, output impedance, distortion, all vary greatly and overlap with other class of amps.
you boys need to play nice....the concept of "which is better" is such a competative, guy-thing....listening to a system is about pleasing the listener; I hope we all recognize there is no "absolute' sound in reproduce music, and ones perceptions are subjective ...we should recognize that some "distortions" are "pleasing" to certain listeners. And some listeners cannot get past preconceived biases, and hear what they want to hear. At the end of the day, it is all about what pleases the listener. I know full well that my room is a serious limiting factor for my sound and I simply have come to accept that....as it stands, good source material sounds wonderful , to me, and that is what matters, I believe....I am not here to "compete" with others.....ENJOY ......
Idk...my sugden A21se single ended class A sounds wonderful to my ears. Probably the best I’ve heard thus far. It somehow is adding something to the music that, at least to me, sounds more natural or organic. Maybe its in the design, maybe its added distortion...who knows? All I do know is that I’m either hearing or at least perceiving a noticeable difference in a good way. This is not to say that my Marantz pm14s1 sounds worse in any way, I’d rather say it sounds different. I will say that the sugden does seemingly run out of some breath at very high volume, where as the marantz seems to have more headroom. However, at a lower volume (where I generally listen), I gotta give it to the sugden. It is doing something right that makes me me want to keep on listening. Its a beautifully designed amp by the originators of SS class A, since 1968. Countless reviewers of the A21 have felt the same way about it as I do, so I don’t think I’m nuts. Is it the absolute "best" amp available?? Of course not!! However, for what it costs and what it does do, it does a darn good job. No bells, no whistles, no dac, no phono stage, no digital whatsoever, All Amp... Also not sure why people harp on how hot it gets..its class A! Always on, always ready. If I want to pay a higher electric bill, so be it. There are some much older a21’s still in use today with zero issues, despite the heat. https://en.m.wikipedia.org/wiki/Sugden_Audio#:~:text=In%20April%201968%20the%20A21,amplifier%20under....
All I know is the Sugden A21SE I’m running with at present is the best sounding amplifier I have owned to date, not that I’ve owned that many amps really but it’s also the best sounding I’ve heard apart from a Sugden Masterclass, yes it gets toastie but at 30wpc at 8ohm it’s got an amazing amount of kick, the kind of power amplifiers like the Hegel H190 with 150 watts struggles to match, but at the end of the day an awful large part of being an audiophile is thinking with the heart and everyone will always have their correct opinion, that’s what makes us spend silly money. 😂
It’s satisfying to see there is still some original member’s left here on audiogon with substantial exsperince, that said, I wanted to thank georgehifi, and bigkidz that know the truth about class A bias amplifier’s. Of all people, me and inna know about over blown publicly about an audio product, we both had a Luxman L-509X integrated amplifier at the same time, we both burned in the amplifier, turned out the amplifier had exaggerated treble that did not sound like the real event that is on stage, the bass was weak and not fulfilling, the mid-range was terrible, the sound stage was subpar at best, needless to say we both sold the amplifier’s at a big loss, 8 or 10 months old New!, I already own my main system through all this witch is pure class A system running class A digital direct to the amplifier that is class A, as bigkidz said in his post, very emotional real sounding system, this system made red neck’s cry, LOL!!!
Class A does NOT sound better (as the thread starter claimed).
He doesn’t mean different manufacturer amps. The same amp/s will sound better without any xover distortion, and the way to get it is with more Class-A bias if all else can take the extra juice that it needs to do take that extra class-A bias, and it will sound better for it.
Just have a listen to the Halo JC1 monoblocks they have a switch on the back that raises the Class-A bias quite considerably, you clearly hear which sound better, same with the Gryphon Antillion with it's switchable bias. Cheers George
I had a lot (or heard -) of class AB amps (high-end): Luxman, Esoteric, Hegel, Audio Analoque, Jeff Rowland, Accuphase, Mark Levinson, d’Agostino,...not of them all ,sounds better than Ear Yoshino 509 monoblocks or Wavac MD 805m. : the purity, detail, 3D. If you really enjoy your music, this is the best. You can’t put it very loud, but you have to to really enjoy it. Tubes get warm and have to be replaced after a while,but a real music lover will take that in. In transistor, I had a few class A amps:some of them sounds to “dark”, detailfull,rather “flat”.
Class A does NOT sound better (as the thread starter claimed). I owned pure class A Krell monoblocks which definitely didn’t sound better than my current Pass Labs class A/B mono blocks. This statement of the threadstarter is way too general ...just like a V8 is always faster than a V12 or boxer 6 ....
Very interesting topic. My partner and I just finished building a pair of mono block El-34 pure Class A power amplifiers. Took them to a customers home to compare to his Jeff Rowland Model 7 mono blocks driving Mirage M-1si speakers, probably like 85 db. The Rowlands controlled the bass a little better (Update - just added a larger capacitor size and the bass was even better with the Class A amps but we would have to go back to compare). The rest as they say is history. The Class A had tone, musicality, dimension, that made the music so beautiful, piano was just stunning. We were stunned on how good an old Cat Stevens CD sounded and a few tracks of the old Jeff Beck CD Blow by Blow, Santana Abraxas, etc. The guys wife's eyes actually teared up.
Oh sure like someone already stated above, it comes down to the design implementation. There are some Class A amplifiers that probably are not as good sounding as class A/B amplifiers, I have not heard every single one of them so who knows but in designing amplifiers, we have not been able to make one that sounds better to our own ears. Do Class A products run hot, sure do. Does that mean they won't last as long, no it does not. As for head room, that depends on the design - that can happen with any amplifier not matter how many watts they are rated. But the pair we just finished are simply killer! My Vandersteen Model 5As never sounded so good.
I am sure George and some others could offer an explanation of what happened beyond just formal power ratings.
Here we go, watch out for the flame throwers !!
Stereophile: Legacy Focus Not only are there two minima in the bass of less than 2 ohms, and another of less than 3 ohms in the mid-treble, but there is an amplifier-crushing combination of 3.3 ohms magnitude and 60 degrees capacitive phase angle at 20Hz. Fortunately, it is rare in music to have high levels of energy this low in frequency.
They Legacy’s might have been 95db, but they were a "savage load" for any amp right through the bass up to 150hz, 1.8ohm load with 40 degrees of - phase angle 55 at 30hz!!! that could simulate lower to the amp in the bass https://www.stereophile.com/images/archivesart/LEG20FIG1.jpg
Especially bad for complimentary push pull Mosfet amp with a lot of A bias they don't do current very well into low impedance. Bi-Polar amp (BJT’s like Ago, Gryphon, JC1 Krells would have far better with these sort of speakers)
And what looks to me like a "average amount" of storage reservoir capacitance for a Class-A especially, may have the watts, but looks like not much for reserve for current. Sure it got 2 trannies but where’s the massive stack of power supply caps https://ibb.co/3rZbwdm https://ibb.co/zF89tFR
I am sure George and some others could offer an explanation of what happened beyond just formal power ratings. I like Loreena and Dante's Prayer track is one of her very best.
I can chime in on this. I owned a Plinius SA-103 @ 220w into 4ohms which is class A biased driving a pair of Legacy Audio Focus speakers @ 95.4 db sensitivity. I always felt like it lacked power. Indeed, there were certain passages where I would drive it to clipping. One of which was Loreena McKennitt’s vocals on the Dante’s Prayer track from the Book of Secrets album. I decided that was unacceptable and that I needed more power. I sold the SA-103 and purchased a SB301-MKII class A/B which is 470 watts into 4ohms. The difference was amazing. I had all of the great Plinius sound and none of the "lack of power" issues. The bass was driven with much more authority, the highs were crystal clear and well defined. I wasn’t quite sure what to expect but now I wouldn’t trade my amp for anything. YMMV but in my experience the additional power of the class A/B amp trumped the class A hands down.
Miller didn't say a bad word. If he wants to sound right - fine. Going too far into the subjectivity will get us nowhere. I mentioned D'Agostino class AB amps as being more than competitive. Maybe his class A amps would've sounded even better. I bet, he didn't want huge size and heat, so he opted not to do it.
There have been only a handful of true class a amplifiers made it takes a lot to make one and very few have ever accomplished it. In solid state amps only a handful and in tube only a handful also they are incredibly difficult to make and unreliable due to heat generation because of the 10 percent efficiency. So most of the makers if not all stopped making them. Now most makers build an amp to play class a to a certain watt level then switch to ab mode because of this and this results in the amplifier still sounding like a class a amp because it is at low powers.
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