I'm upset because I just found out you can't run a Class D amp in pure Class A
Class A or Class D solid-state amplifiers (modern designs)
Hey guys.
Class A is supposedly superior. Something to do with a conduction angle of 360 degrees...so the entire signal gets processed in one go without crossover distortion.
But in terms of sound quality (subjective enjoyment) is there a benefit to Class A? Can class D provide the same level of enjoyment?
The dealer I’m talking to says that really nice Class A amplifiers are designed for "reference quality" meaning completely true to the real life performance.
Let’s compare and contrast. Which one is technically better?
In other words, could you have equal technical performance and quality in a Class D amp?
- Jack.
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Did you ever do the comparison of the Gran Vivace to the CODA #16? I also own the #16 and a PeachTree GAN1 (modded). The modded GAN1 is almost as good as the #16 but a real PIA to use because it is more than an amp. I am looking to get a GAN amp and the Gran Vivace is something that I am considering. Main reason for the GAN decision is because the Peachtree GAN1 sounds really good, and I need something with a very small form factor and some power behind it. The CODA #16 will stay in my office system. I need an amp for my Livingroom system. |
I just spent several months comparing the AGD Audion mono blocks to my Coda #16 amp and have made my choice. The AGD’s are very, very good. I think they sound spectacular but my Coda has something that I prefer. There is a deep dynamic snap that the Coda produces that I love. It is the best SS amp I’ve ever heard. There is a considerable price difference here and the 110 lbs of the Coda means I’m not moving it by myself. My dealer says he’s bringing the AGD Gran Vivace over for a listen so we will see how it stacks up to the Coda. Price wise it’s more apples to apples. |
Every time, and I mean every time, I put my Musical Fidelity A1-2008 Class A SS amp back in the system (replacing either a QUAD 909 or Transcendent Sound T8-LN OTL tube amp) I listen for about 10 minutes and then say "holy crap!" I forgot how incredible this sounds! Pretty amazing when a solid state amp can equal or even in some areas even best t a high end OTL Tube amp.
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For Purifi and Atmasphere at least, the “ass-wipes,” are simultaneously on the board and also the ones in the lab. |
IMO and IME, well built high pulse draw systems do indeed hold up very well. To the point, IIRC, that they are extensively used (if not entirely ubiquitous) in the satellite business. However, the minds that execute a given class D amplifier circuit, or whom chose it’s parts values and it’s layout, tracing sizes, mass, interactions (placement, length, etc), and what have you..may not all be on that level of ’a deep history in milspec and beyond’ of knowledge and skills applied. Where the end users buy by price being a major factor. Which, when it comes to peaks and pinnacles can be a rather foolish position, but also..sometimes.. prudent. It's tricky. Our end effect, as we cascade down that path of logic and reality... is to have the market filled with class D amplifiers that individually sound different, with wide spectrums of distortion products that allow them to differentiate themselves from others. With quite a few designs that don’t (operationally) last very long, compared to their older amplifier brethren of non class D nature.. With a difficult path to refurbishment or repair, in many cases, re general knowledge in technical types to deal with repair efforts. If the past is any guide, I expect that class D will finally surpass the desires of most of even the high end audio crowd, re sound qualities heard, but not yet..not yet... I’m well familiar with this effect of even the high end crowd finally being swayed, as I come from the ’CRT projector is king’ high end projection market. Where I was making some of those ’pinnacle’ CRT units myself. Then digital projectors came along and dominated the bottom of the market, and then slowly became better and better and dominated the meat of the middle of the market... and then slowly crept into the high end market. Where analog projection has to fight to beat out the best in digital projection technology and the battle...- is over. Digital projection wins, even at the very peak, in almost every way possible. I saw the writing on the wall in 2003, and began switching form working on modifying the peak of analog projection to working on digital projection technology, to improve it. In that, in the last while...I purchased a 2014 DLP projector and even a 2018 4k DLP engine/hardware design package, and analyzed both. I found that the innovations I came up with in 2005-2006, where I had stopped working on DLP engines, all that work was still viable and not anywhere near being included in any DLP engines that I was aware of. So their upward trend in qualities was and is moving quite slow, and my design change works were still valid and useful to improving modern DLP projection. After all that time. sheesh. Either I’m quick or they are slow. I nearly ended up working with Delta (approx 65% of the DLP projectors on the market are made by them), but I was being treated in the usual way that the inventive type are treated by, by the given major corporation. That I was just the simple vessel for the message that was intended for them. Not looking for self aggrandizement but just a simple fair deal. But..no. Typical corporate systems, is what most innovators will run into. A given boardroom of ass-wipes who are paid for how aggressively they can steal from and malign any innovator who is foolish enough to get close to them. It’s kinda like what was said in the film ’Pi":
And they don’t care, they are selling projectors regardless. and, the more technology they can own, or if not.. push to it’s death into a ditch, is all, well...just fine. This is what inventors find out when they approach corporations. Class D amplification might take the same sort of path of not being as good as it could be and not innovating as quickly as it might. Accordingly.. it’s not quite there yet as (observed/heard sonic qualities) pinnacles may go. Never say never. I spent two years constantly working on class D amplifiers cleaning up their ’flaws’ and I have no place to put those innovations as it’s the same problem that all inventive types that don’t work for corporations - run into. Not whining in public here - - that’s the way it is.... |
Electrolytic caps last longer if they have a charge on them and they are not subjected to heat. WRT the other parts used, surface mount has been around for several decades and reliability seems to be at or better then the level of reliability of thru-hole parts. I expect class D amps will hold up very well. |
My comment was about amp history. I don't know when the cascode amp paper was written, but the Threshold CAS-1 & CAS-2 amps date from the early 80s. I don't know the history of class D amps, but am not surprised a paper likely written ~40 years ago about audio amplification didn't include class D. I do have a question for you, if you don't mind my asking. As we all get older, we're discovering that parts inside our stereos age (and worse) as well. What have you been able to glean about the long term reliability of class D amps, what goes wrong, and what is the result? I know it's probably a lot of the same parts, but they're being used differently. |
@petaluman As you might expect I have read Nelson's article before. He addresses the issue of poles in the amplifier caused by adding more stages of gain and how that adversely affects the use of feedback. I addressed that issue in my first post to this thread. A class D amp only has one stage of gain FWIW. Nelson does not address the solutions class D offers to the issues described in his article. |
Matter of taste between A, A/B or D. But like many have suggested, technology has allowed for Class D to push the limits on competing with many high end amps. However, I would choose class A any day. Just knowing the parts used inside along with the design and heft that goes with it. I would rather spend my money on that knowing the heft is whats behind my amp. And also not all companies build Class A amps so thats a thing of beauty along with the pure sound. I've own many amps in my time, you'll be hard pressed to find a build like a Luxman 590. IMO |
"Lowering distortion in power circuits without compromising their transient response remains a primary problem for designers of audio power amplifiers. Until fairly recently, the favorite technique for removing distortion components in linear amplifiers was to cascade many gain stages to form a circuit having enormous amounts of gain and then using negative feedback to control the system and correct for the many errors introduced by this large number of components. While the sum of these components’ distortions may cause large complex nonlinearities, the correspondingly large amounts of feedback applied are generally more than equal to the task of cleaning up the performance with only one trade-off—the high frequency performance of the system. Because each amplifying device also contributes its own high frequency roll-off, and because the sum of many of these roll-offs creates a complex, multi-pole phase lag, a system using large amounts of negative feedback tends to be unstable at high frequencies, resulting in phenomena popularly referred to as Transient Intermodulation Distortion (TIM). As this phenomena has been well described elsewhere, it will be sufficient here to point out that two solutions to TIM problems exist. The first solution is to not require any high frequency performance of the circuit, that is, not to feed it high frequency signals it cannot handle. While this solution works very well for many operational amplifier applications requiring only low frequency performance, it is judged to be unacceptable in high-fidelity applications where frequency response is required beyond 100 kiloHertz. Although human hearing is generally very poor above 20,000 Hertz, ultrasonic frequency roll-offs produce phase and amplitude effects in the audible region; for example, a single pole (6dB/octave) roll-off at 30 kHz produces about 9 phase lag and 0.5 dB loss at 10 kHz. The effects may be subtle, but their audibility is undesirable in a piece of equipment whose performance is judged by its neutrality. Because of this bandwidth requirement, designers of state-of-the-art amplifiers are turning to the other solution; simple circuits having few amplifying devices and relatively low open loop gain. The simplicity and low gain allows the circuitry to respond to signals very quickly, thus eliminating transient problems, but it does so at the expense of higher harmonic and intermodulation distortions."
Nelson Pass, from "Cascode Amp Design" |
@ Coltrane1: "This is a troll question and insult to any audiophile." Well that is either a deliberate trolling post or just a very ignorant one. |
@coltrane1 You really have the "Hey kids, get off my lawn!" vibe nailed. Atmasphere is now making Class D as are others with sterling reputations. So....they're all crazy or craven, eh? |
If ”The Audiophile” is running those big refrigerator boxes with <=2 ohm impedance, which requires lots of watts, then the euphoria of Class-A, or 5W SET amps, is just not going to happen… it will be going from euphoria to anorexia. |
This is a troll question and insult to any audiophile. How can you be an audiophile and not already know which design is superior? Everyone knows Class A is pure euphoria. Stop this noise about Class D. But in the end you make a choice and pay your money. Mine is on Class A and tube amps. That’s all the audio anyone needs. Period. Spare me of your newfangled crap D. |
Class A is like a muscle car. There are many that are absolutely beautiful, perform really well and others that are just gas guzzlers. Class D is like an electric car. The same applies as Class A except the gas guzzler aspect, so that is replaced by the utilitarian electric car that under performs and has no mileage range.
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I can’t do better than Atmasphere’s response. But I will add my 2 cents. I have built several Nelson Pass diy designs, both power amps and preamps, all Class A of course, and I use them in two different systems in my home. I will say there is a sweetness to these amps, but I will also say it could well be that it is due to their relatively low power. These are such simple circuits they are “messing” less with the signal. Pair them with a speaker in the 95 dB sensitivity range and you’ve got a winner, IMO. But move on to my listening room, and Class D shows up, a Rogue amp with their combo of a tube input stage and Class D output stage. That’s largely because I prefer Magnepan speakers for serious listening and they need power. And I see no sense in running a Class A amp with anything close to 100 watts. For one, the constant draw of electricity is contrary to any semblance of environmentally responsible energy use. And I auditioned plenty of amps, and find these hidebound descriptions of the supposed differences in amp classes comical. Honestly, it’s like your mechanic in the 1970s and 80s advising you to buy an American car with a V-8. Sure, he’s an expert, but in what? Why, fixing trouble-prone American cars, of course. Technology changes. Better ideas come along. Class D is one of those. |
“LSA Voyager GAN 350 wpc class D is a kick ass amplifier. I have had multiple highly regarded class A amps and tube amps. Not yet heard other GAN class D amps.” Respectfully, I owned the LSA Gan 350 and put it in my professionally calibrated audio system. My Parasound Halo A23+ amp wiped the floor with it. The Gan350 did have a smooth grainless top end but it ended there. It did not “project” music like the Parasound did. The Gan amp was boring. Wasn’t engaging I. Comparison. Bass was more muddy in comparison. Mids were more recessed and top end, while smooth and grainless, was just boring and did not engage. Lacked bite. It also has more hiss when I cranked the volume with no source playing. I tried to like it but it wasn’t to be. The Parasound remains in the system. |
@tweak1 - thanks so much for your reply - your comparative experience is really helpful to me - at some point I am going to add a GaN to amp mix & owners of the LSA all seem very happy with the choice - Have a great day! |
Sorry Ralph while I am familiar with your work, I have no first hand experience. But you are one of the few who manufacturers quality from what I can see. I remember also using Caddock resistors back in the day also. spenav - while we have been asked to have our components reviewed many times, we have not had our components reviewed. I understand that your mom is your greatest fan also. While we have our opinions on the comparisons, most of my comments regarding the sound of our components comes from people who bring their equipment over to hear with the speakers in our listening room, Sonus Farber, Horning, Vandersteen, Alon, Dynauido, Klipsch, Verity, Rogers, ProAc, etc. They come to our listening room to hear the differences. We also provide upgrade service and repair service. For example, recently and highly regarded DAC was brought in and after hearing the differences, we were asked to upgrade that DAC. Same goes for many other components. That allows us to also hear things and we actually learn more of what can be accomplished. Again, we are not there to pound our chests but to help others improve their systems. It is very enjoyable to us. Regarding reviewing our products, we barely can keep up with the work we have now. Hand made products take time to manufacturer. It is a labor of love for us. I hope that I have explained ourselves so that everyone understands that we are in this together and not for us to think we are better than anyone in anyway. I realized a long time ago, that what we do is really for us first. We are always learning and improving. We are always open to hearing new things
Anyone who is in the NYC area, contact us, we are more than happy to host a visit.
Happy Listening.
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😉 We've been building point to point wired class A triode amps for 48 years. Custom built chokes and transformers, V-Caps, custom copper wire made to our specs for hookup; we were the first to use Caddock resistors in the audio industry (1978) and garnered many awards and reviews in the high end press over the decades. Totally FWIW department... |
I have owned quite a few class Ds including; several W4S, PS Audio M 700s, Emerald Physics 100.2 SEs, EVS 1200 (based on dual mono IceEdge AS 1200 modules) plus loads of tweaks. I raved about for over a year, UNTIL, I got a LSA Voyager 350 GaN amp, which was about half the power, but easily twice the authority. It is so night and day from the EVS, that IMO, GaN (at least this one) should not be included in the class D designation |
Thanks for the reply. I have one last question: have any of your creations been reviewed by a third party outsider with no horse in the race, like a magazine? I am asking this because if you only listen to and compare your amps in your environment and with your specific associated equipment, that gives you a home court advantage. To my mother, I am the most handsome man on earth. While I accept your testimony, I would be interested in knowing what others think. |
