jaybe stated:
" Yes. I sold them because they just can’t compete with high quality class A/AB amps when used for their full frequency range. Maybe using them to power your subs would be OK."
This is a misinformed and ignorant statement that was typical of comments made about class D amps from about 5 or more years ago. It is completely irrelevant to the current capabilities of the many good class D amps now available at very affordable prices.
Just like every other product people buy, there are variations in quality and performance of class D amps that run the gamut from poor to exceptional. Obviously, the class D amp that jaybe chose to buy and later sell was from the lower end of this quality/performance continuum.
For the past several years, there are numerous good quality class D amps available that outperform most good quality class A/B amps in every category most of us care about: lower distortion, better bass performance, more accurate/detailed from bass through treble, lower noise floor, greater dynamic range and more neutral overall sound characteristic that is closer to the traditional audio ideal of ’a straight wire with gain’.
I base my comments above on my personal experiences as a lifelong good quality class A/B amp user who first discovered the superiority of good class D over good class A/B about 3 years ago. I have since replaced the 3 stereo class A/B amps with 2 stereo and a pair of mono-block class D amps in my combo ht and 2-ch music system.
I still have one 1,000 watt class A/B amp in my system that powers my 4 subs but I’ll be replacing that with a class D amp soon.
To answer your original question, All of the Hypex-NCore based class D amps are very good. But there are other very good class D amps now available that are based on other class D power modules such as the latest Ice UcD, Abletec/Anaview and Pascal power modules.
If you’re looking to try a class D amp, I can recommend specific brands of amps if you give me a budget range, your room size and speakers. I’m not a retailer, just a big class D fan
Tim |
Hi bache,
I wanted to elaborate a bit on hgeifman's post above just in case you might google his amps and get scared off by the msrp price of $16,500.
The 6 Moons review on these class D mono-blocks that I read concluded that these may be the best amps you can buy regardless of type or price that they have ever reviewed. This clearly positions them at the high end of the quality/performance continuum I discussed in my last post.
Mola Mola is actually a company founded by the inventor of both UcD (universal class D) and Hypex-NCore technology, Bruno Putzeys, and Hypex founder Jan-Peter von Amerongen. Hypex supplies their top of the line NC-1200 power modules and SMPS (Switch Mode Power Supplies) NC-1200 power supplies to OEM amp manufacturers such as Acoustic Imagery, Merrill Audio, Jeff Rowland, Bel Canto Design and Theta Digital for use in their high quality class D amps.
The Kaluga monos utilizes custom class D power modules designed by Bruno Putzeys that are not available to OEM competitors.
Class D technology has also progressed to the point that Hypex modules now have serious competitors that some believe even outperform them such as the latest Ice UcD modules used in certain Red Dragon amps, Abletec/Anaview modules used in certain D-Sonic amps and the Pascal modules used in certain Jeff Rowland and D-Sonic amps. In addition, class D technology is continuing to be developed and other class D modules/amps may be available in the near future. There are also Hypex NC-400 power module amps available from custom assemblers such as James Romeyn that approximate but don't match the performance of NC-1200 module amps.
The good news being that there are significantly less expensive very good class D amps currently available that are positioned somewhat lower on the quality/performance continuum than the Mola Mola Kalugas and Merrill Audio Veritas amps but still provide very good performance.
Tim
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@noble100 How inappropriate. In fact I’m not ignorant, I speak from fact and after ownership of several higher-level N-Core Class D amps within the past year. None came close to giving the musical pleasure and satisfaction of my current Class A/AB amps. You can grandstand and type away until your fingers are red but it won’t change my opinion." Hi jaybe, I had no intention of offending you with my prior post. I think it just strikes a nerve with me when I read comments that repeat that old refrain about class D amps being only good enough for subwoofers and not for reproducing the entire audio spectrum with high fidelity. I consider that criticism valid for some earlier brands/models of class D amps but not valid at all for the class D amps I own as well as many other current brands/models. I agree that good sound is subjective and system matching is important for achieving the system sound you prefer in your system and room. I also believe there may be poorly understood and unidentified sound artifacts with class D amplification that some are able to hear that others, like myself, are unable to detect. At this point, it's hard to prove but still a possibility. I think it's important to tell you I was not calling you ignorant, I was careful to call your statement ignorant. The difference? I believe you're experienced in audio matters and capable of knowing whether you like the performance of a component or not but conveying that good quality class D amps are only useful as sub amps is not accurate anymore, at least not for all individuals. I also may not have been clear enough in my post that I was making comparisons between good quality class A/B amps like the Aragon and Adcom amps I replaced with good quality class D amps such as the Class D Audio, Emerald Physics and the D-Sonic amps I replaced them with. I don't know which class D amps you auditioned in your system and whether they'd be generally considered good quality class D amps. However, I noticed you finally settled on a Pass class A/B amp for your system. I would consider almost any Pass class A/B amp to be beyond 'good' and suggest you were comparing a possibly good class D amp or amps to 'one of the best' class A/B amps available. I'm not surprised you preferred the Pass in this comparison but would point out that this is a somewhat apples to oranges comparison. I think a more worthwhile comparison for you would be between your Pass amp and Mola Mola Kartuga or Merrill Audio Veritas mono-blocks that are in a more similar quality and price range. You seem to be very pleased with your Pass amp's performance in your system and I have no interest in trying to persuade you to do anything but enjoy it. Tim |
" All Class-D’s today have the same problem. The switching frequency is too low to be filtered out effectively completely with the Class-D’s output filter, without effecting the upper mids and highs.
In the future when technology allows the switching can then be much higher to allow the output filter to do it’s job properly and cut out all the switching frequency noise without effecting the audio band."
Hi George,
As we’ve discussed on several other threads here on Audiogon previously, I’m still not convinced of your theory because of 2 reasons:
1. I have never heard any sonic anomalies in the mids or highs in any class D amp I own or ever listened to and I’ve never heard anyone claim they exist except you.
When I first read of your theory on another thread, I spent significant time listening to my system for anything remotely amiss in the upper mids and treble but never heard a hint of any issues. Since I can’t hear what you vaguely describe as ’affecting the mids and highs’, then these purported sonic anomalies don’t exist for me and likely many others so there is nothing to be remedied with higher switching frequencies.
I’ve previously requested you describe what these sonic anomalies specifically sound like so I can more easily identify some semblance of one. You have failed to respond every single time; which could mean your theory is false and you can’t describe the anomalies because they don’t exist, your theory is true and there actually are anomalies but they are inaudible to humans or you just fabricated your theory and are just messing with us.
In an effort to keep an open mind on the subject, however, I stated the following in my prior post:
" I also believe there may be poorly understood and unidentified sound artifacts with class D amplification that some are able to hear that others, like myself, are unable to detect. At this point, it’s hard to prove but still a possibility."
2. There is absolutely no scientific evidence or even any mention to support your class D theory that the switching frequencies are currently too low and cause negative affects in the audible frequency range.
Need proof? Google "class D switching frequencies are too low" and you just get references to your audio forum comments, no scientific or really any evidence whatsoever to support your theory.
I included my statement in my last post in an effort to be fair and remain open minded but you’ve made me regret it. Your continued adherence to a theory you are continually unable to prove at some point becomes pointless and is just a theory best abandoned.
Are you still unable to describe what these upper mids and treble anomalies specifically sound like? Have you ever actually heard any yourself? Please do not respond until you’re able to present, or at least attempt to credibly falsify, some evidence to support your theory.
Tim |
Hi mitch2,
You have an excellent system.. I've never listened to either the class D Acoustic Imaging Atsah or the class A Clayton M300 monos but I've read many very positive reviews on both.
Just the thought of comparing the diminutive Atsah class D monos at 1/4 the weight and size of the pure class A Clayton monos seems like a big mismatch to me reminiscent of David vs Goliath. I suspect you were not very surprised that, in this modern rematch, the favored Goliath clearly beat the underdog David,
I appreciated your articulate description of your impressions of the sound portrayed by the Atsah:
"In my case, I described what I heard as a soundstaging type of issue where the music sounded as if it were being played by individual players recorded separately in a sound booth, instead of a band playing on a stage together. The ambient cues were not present in relation to the musicians to the extent I was familiar with from my other amplifiers."
Besides giving me a clear understanding of why you were disappointed by the Atsah's presentation, the thought struck me that this poor performance may be a result of a very revealing amp combined with poorly engineered and/or poorly recorded source material.
In an effort to be totally honest about this, I need to assure you I'm making my comments less as a definitive explanation and more a joint exploration of the forces at work in your system.
I don't have the experience with NC1200 based class D amps that you have but I've used 3 mid-level class D amps in my system for the last 3 years. I'm familiar with how very neutral and revealing these amps can be of upstream components, system cabling and especially the quality of your source material; a well engineered recording will sound exceptionally good but a poorly engineered recording will reveal its flaws just as faithfully. I've occasionally experienced a similar affect as you describe on obviously poor recordings played through my D-Sonic M-600 monos that utilize the newer Anaview/Abletec AMS-1000-2600 power modules.
My suggestion is actually more of a question to you than a statement:
Could it be that the reason the musical material that you played through your class A Cayton M300 amps sounded so good, while the same recording played through your very accurate and revealing class D Atsah sounded so poor, was due to the musical material not being as well engineered as you originally thought? In other words, Do you think your class A Clayton M300 amps are less revealing and more forgiving of bad recordings than your Atsah?
Your other impression on the Atsah, that "the ambient cues were not present in relation to the musicians to the extent I was familiar with from my other amplifiers." I find this perplexing since, typically, good class D amps are very accurate, neutral and detailed, not known to add or omit anything to the audio signal.
I find it very interesting and informative that you own and have compared 2 such diametrically opposite amps: The high powered, large and heavy Clayton M300 monos which are pure class A, highly praised for their excellent sound performance that are the least efficient of amp types and the high powered, small and light Acoustic Imagery Atsah monos which are class D, praised by many for their very good sound performance that are the most efficient of amp types.
I recently read a quote from Bruno Putzeys, the inventor of th Hypex NCore class D technology, that may be of interest to you and other readers of this thread:
" I can emulate the sound of pretty much any amp out there if I wanted. But so far I'm resisting. If ever I give in, it'll be obvious from the measurements and I hope someone calls me out on it. Anyhow that's why I decided I actually wanted the NC400 to have this unvarnished dead-pan delivery."
Putzeys interestingly stated the main benefit of using class D is efficiency.
He also stated he tweaked the Hypex NCore 1200 module in his Mola Mola Kartuga monos to differentiate his amps from the numerous OEM class D monos on the market that utilize his standard NCore module.
Perhaps someday soon he'll tweak some modules to emulate the sound of the Clayton M300 pure class A monos in either his own or one of his OEM customers' amp.
Sorry this post was so long,
Tim
I |
My opinion is that, for a thread that just asked if anyone had experience with Hypex class D amps, the numerous responses have instead provided a wealth of useful information from individuals that have experience with class D amps in general which has expanded the discussion well beyond just Hypex based amps and arguably was more informative to anyone considering a good class D amp.
I've enjoyed the discussion thus far and hope the OP, bache, feels the same even though the responses have expanded beyond his specific question.
The responses have been wide ranging, from class D is only good enough for subs, to class D is good but I think my class A or expensive class A/B or tube amp is better to class D is very good and I sold my old amps. I think these are all valid responses that are accurate and truthful with the exception of the first one.
This thread has reinforced my opinion that exceptionally good system performance can be achieved with the use of the better class A, class A/B, tubed and class D amps. I think the biggest benefit of class D is its efficiency and many might prefer an alternative sound for their systems.
I believe the better class D amps are so accurate and neutral that they may not be the proper amp for those who prefer a touch of flavor to their system sound that some of the better traditional amps possess.
I understand the appeal of high quality traditional amps and would likely own one if my budget was higher. I like that everybody's system can be as unique as a snowflake and tailored to their preferences.
Tim |
Hi merrillaudio,
Good information from an experienced and respected class D company (makers of the Veritas and Thor monos). I agree that class D is still a maturing technology that requires a complex design but has great promise.
I'm curious if you have any insight or thoughts on even further improvements in class D amp performance I've either heard discussed on audio forums or read about on more scientific sites:
1. Would higher switching frequencies benefit class D amp performance?
This is a topic which has mainly been propagated by one individual repeatedly not only here on Audiogon but on numerous other audio forums as well. This theory states the current class D switching frequency (typically in the 500-600 Khz range) is too low and negatively affects frequencies in the audible range. I've had difficulty accepting this theory because I've never heard any evidence of this in any of my 3 class D amps, am unable to find any supporting scientific support for it and the only expert comment on switching frequencies I've been able to find thus far, from Hypex NCore and UcD inventor Bruno Putzeys, is that a 'reasonable switching frequency for a class D amplifier is just under 500 Khz or so,
If you go much above that, you run into efficiency and headroom problems".
I'm trying to keep an open mind but was hoping you had some clarifying input on this matter.
2. Will the use of eGan FETs be utilized in any upcoming class D power modules that you're aware of?
These are the new Gallium Nitride FETs that switch on/off much faster than the current MOSFET transistors used in class D power modules. If these switching output devices sound equally good or better than MOSFETS, it seems to me that could only benefit performance. Just wondering if you know of any near future amps utilizing the new eGan FETs.
Thanks,
Tim
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Hi bache,
Sorry, I haven’t heard any of the Nord amps but I’d really like to.
I believe such a class D amp is possible because the inventor of UcD and Hypex NCore technology, Bruno Putzeys, has stated he can design his class D amps to sound like any type of amp.
I think the use of class A circuitry before class D power modules has a lot of promise. A well designed one could result in an amp that closely resembles the very good sound characteristics of a good class A amp without the many downsides typical of class A amps: big, heavy, inefficient, expensive and hot running.
In my limited experience with class D amps, I would describe the overriding sound characteristic of the 3 versions I own as extremely neutral. My examples do not add or subtract anything from the inputted signal that I’m able to detect. There are other obvious common characteristics I notice such as a very low noise floor, wide dynamics and a high level of detail, but I still consider a neutral presentation as their main quality; very similar to the Absolute Sound’s description of an ideal amp: "a straight wire with gain".
I’ve found this neutrality has allowed me to quickly notice the affects of all upstream changes to my system, such as components, cables, power cords and the quality level of recordings played.
I fully expect Nord’s placement of class A circuitry in sections prior to the power modules to affect their amp’s overall sound. Whether this results in a sound that closely resembles that of a high quality class A amp can probably only be answered by auditioning one in your system.
I’m going to search for professional reviews of Nord amps with class A circuits.
Tim |
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We will shortly be introducing our proprietary designs which takes the level of performance up an order of magnitude, and rivals any of the best of classes available. Using our proprietary ZXOL design that has no feedback loop, we are able to achieve this exceptional performance."
Hi merrillaudio,
I'm a bit surprised you're going to cease using Hypex NCore 1200 power modules in your amps and use your own proprietary ZXOL design modules, instead. I'm not questioning this decision but I am curious why you decided to go without a feedback loop.
I'm not an engineer or amp designer but I have a strong interest in class D technology. I recall reading an interview with the inventor of Hypex NCore technology, Bruno Putzeys, in which he explained why he believed there was no such thing as too much feedback in the design of his class D circuits.
Are you currently able to state your reasons for deciding to eliminate a feedback loop in your design?
Thanks,
Tim
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Hi Ralph, Thank you for your informative response. I've been reading for decades that negative feedback in traditional linear amps should be avoided since it (sorry, no pun intended) negatively affects its sonic performance, especially in the upper frequencies. I've taken this as the gospel truth ever since I first learned about the use of feedback in amps. Since I've become interested in class D amps in the last few years and began reading about how it works, however, several articles and white papers I've read have caused me to rethink my view of negative feedback in class D amps. For example, here's a quote on this subject from an interview with Bruno Putzeys, inventor of UcD and Hypex NCore technology: "If you take a simple amplifier which has acceptable distortion (just a second harmonic is what I use as an example) and you start applying feedback, harmonics will appear that were not there originally. Higher-order harmonics, even and odd, turn up out of the blue. So if you apply a little bit of feedback, the second harmonic that you wanted to reduce drops by a little, but out of the blue you get this whole smattering of high harmonics. It is quite understandable that this doesn’t sound good. That observation has been made and published by various people over the years, but the most important conclusion was never drawn: If you keep increasing feedback, if you turn the feedback knob up and up and up, you quickly hit a point where those distortion products all start coming down again and the signal does start getting cleaner. And if you get to very large amounts of feedback, the result is just supersmooth. So that is why I say that it is normal for an experimenter to experience that if you take a good-sounding zero-feedback amplifier and add 6dB of feedback, the result sounds worse. They heard that right. But had they been in a position to add 60dB, well then, suddenly they would have been confronted with a sound that is little short of magical." I've always respected your audio knowledge and found your posts very informative. I have no desire to start an argument with you and I'm fairly sure you've forgotten more about good amp design than I've ever known. I'm just very interested on your thoughts about negative feedback in class D amps. Here's the link to the entire Bruno Putzeys interview I quoted from above: www.soundstageultra.com/index.php/features-menu/general-interest-interviews-menu/455-searching-for-t...Thank you, Tim |
"Bruno is spot on with this. The usual rule of thumb is that very low amounts (under 4 db or so) is not harmful, but more than that is a problem; after about 20 db or so things start to settle down. 60db hasn't been practical until the introduction of class D (since gain is developed in an entirely different way); so I have no argument with this; my prior comments should be limited to traditional amps where making the kind of gain is impractical."
Thanks, Ralph. Your statement has cleared this issue up for me.
darknightdk,
Although I use more mid-level class D amps than your Acoustic Imagery Atsah mono-blocks, your described impressions of your class D amps as "being extremely revealing, neutral and transparent and will take on the character of the source equipment, cables and material being played" closely resemble my impressions of my amps. Like you, I've been amazed how clearly audible the performance level of upstream components, cabling, power cords and recordings can be heard and judged as well as how clearly audible the affects of any changes to any of these can be heard and judged. The best description I can think of is the proverbial 'straight wire with gain'.
This level of clarity and detail is not for everyone and any upstream weak links in your system will definitely be exposed. I prefer this honest quality in my system rather than a masking or inaudibility of weak links; weak links can always be upgraded in quality but only if you're aware they exist.
Enjoy,
Tim
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First you need a bit more clarification on just what "feedback" are you talking about, "global feedback" or Local feedback"? As both are very different.
"local" is a good thing if the output stage is designed right with minimum problems. "Global" is also ok if used sparingly and not use to correct big problems."
georgehifi,
According to Bruno Putzeys,
"Local feedback with a bit of global feedback is, actually, identical to full global feedback -- mathematical fact."
I believe he utilizes this approach in his class D designs. He also believes there is no such thing as 'too much feedback' as it pertains to class D amps.
Tim |
