Hypex N core module


Did you have experience with amplifier based on Hypex - NCore Technologies  
591a00e8 7d91 4804 acd5 68a0a631b9e1bache
You can run a search here. There have been many using those for some years, although the brands escape me now. You can search NC500 and NC1200 which are the OEM modules.

FWIW, for my active system I assembled a pair of Hypex UcD400HRx (I think they were HRx...) for my midbasses and very happy with them. Tubes for mids/treble though. I've had them for about 4 years, trouble free, and wouldn't hesitate in buying again from Hypex, nor assembling their DIY modules.
After some discussion, my friend loaned me his James Romeyn Class D mono block Hypex NC400 power amplifiers and I liked them very much. They sounded much better than my Luxman 590ax Class A integrated amplifier. The music was more open, detailed with much improved bass. I was very surprised and could not believe it.

I consulted with James Romeyn and decided to buy his Hypex NCore NC400 dual mono block power amplifiers with 2 NC400 amps per side with the NC1200 power supply. He recommended his Class D dual mono version for improved sound quality.

The amplifiers finally arrived and they were a step above his mono block power amplifiers. The sound quality from my Hypex NCore NC400 Class D duel mono block power amplifiers is amazing.

My sound system sounds much improved over my Luxman 590ax Class A integrated amplifier. I am hearing details, imaging and bass that I have not heard before. My system now offers breath taking detail, transparency, lack of noise, and excellent dynamics that I did not hear with the Luxman 590axClass A integrated amplifier.

I purchased the Hypex NCore Class D amps from James Romeyn Music andAudio, LLC (James). He was very helpful answering my many questions and I suggest you contact him for more information on his assembled Hypex amplifiers (he offers 3 models at different price levels). The dual mono version is $2,980. See:

http://jamesromeyn.com/product/hypex-professional-build-service/#tab-description

Eventually, I replaced my Hypex NCore NC400 dual mono block power amplifiers with the Mola Mola Kaluga power amplifiers. These amplifiers use the Hypex NC1200 and NC1200 power supply custom built by Bruno Putzeys at Mola Mola. The Mola Mola power amp is excellent and highly recommended.

https://www.mola-mola.nl/kaluga.php
After trying few Hypex N-Core and other class D module amps, I end up preferring ATI 52NC or 54NC series amps. They offers best in class performance with robust power supply like no other in this price range. The build quality is exemplary.

In comparison, you will find most Class D amps being sold are made from off the shelf kit packaged in a ‘cheap’ metal box.

http://www.ati-amp.com/AT52XNC.php

Good luck with your search!

@bache, try to get an audition of the Mola Mola, outstanding amplifiers.
Take a look at the new Icepower 1200AS. There's a new kid on the block.
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.
What model you kept and sold? Merill, Mola, Mola? Nord?
1200 As is no High End , you take a look  N-core Hypex OEM
NC-1200 or NC-500 , 
Sold Acoustic Imagery NC1200 to go back to the more natural sound of conventional Class A.
What you get for class A , Tube or Solid State?
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
@noble100
I agree with noble100 above. My Mola Mola Kaluga class D power amplifiers Sound much better than my Luxman 590ax Class A integrated amplifier. The music was more open, detailed with much improved bass. I was surprised and could not believe it.

Of course, everyone has a different opinion, and system, and I encourage you to audition one of the high quality class D amplifiers mentioned above.
@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.

@hgeifman I might agree with you about Luxman. I’ve yet to hear a unit of that brand that wasn’t deficient in some manner, although their product range is huge and I haven’t heard them all. Most common is a “grainy” character that even a Class D amp could beat in this aspect.

But let’s face it system matching has to be considered. And, there’s just no accounting for taste. In the end all opinions are just that.

@jaybe

You get no argument from me.  Everyone has a different opinion of what sounds good in their system and home environment.   Some people like Class A, class A/B or Class D.   The important thing is that everyone needs to find what they like so they can sit back and enjoy the music.    
 I  dont hear any difference between Hypex- N-core NC-500 and \
High End Class A/B- in middle and Highs , but in bass N-Core
overperform  is more tight and accurate , But some guys like more
heavy  
I will try and explain my experience. I was happy with my Theta Prometheus monoblocks. They are very good at bass frequencies along with a very wide soundstage. The upper end was smooth and non fatiguing. I had them when I was setup with a multichannel system. I must add that I am much happier with my D’Agostino Progression monoblocks and going back to stereo only. They are obviously much better in the midrange, and are more dynamic from top to bottom. They are smoother and more powerful than the Prometheus and have an high end with a more natural sounding reproduction overall in comparison in instrumental tone and vocals. Now when I listen to music, my senses are awakened and it seems my "foot tapping" on the floor is natural and instinctive. The amazing difference I have discovered is that when both amps were pushed with the same exact disc (Red Violin track 20), the Theta was slightly strained when pushed on this one track, and it's dynamic orchestral peaks. Of course with the D'Agostino Progressions that doesn’t happen. Each instrument can be clearly heard and effortlessly. I am waiting for someone to chime in on the price differences. You do get what you pay for in this instance. It just depends on how deep one's pockets are!
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     
      
" @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
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 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.


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.

Cheers George  
" 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 noble100, to your statement;
I’ve previously requested you describe what these sonic anomalies specifically sound like so I can more easily identify some semblance of one.
I can add that for over a year I owned and used in my main system a pair of the Acoustic Imagery Atsah monoblocks made from Bruno Putzeys' highly rated Ncore NC1200 amplifier and power modules - the very same modules used in Merrill''s Veritas amplifiers and in the Mola Mola Kaluga amplifiers.  In fairness, the Mola Mola amps have some other tweaks inside that the Merrill and Acoustic Imagery amps do not have, but those who have heard all three of these amplifiers made with the NC1200 modules mostly say there is very little if any difference between them.

I sold them after a prolonged, direct comparison with three other Class A and AB amplifiers.  I liked everything about the Ncore amplifiers, except ultimately the sound.  I really thought these were going to be my last amplifiers and I was very disappointed when it didn't work out that way.  From those of us who do not believe these Class D amplifiers are ready to compete with other very good Class A and AB amps, I have heard varying explanations.  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.  Another, similar explanation that also describes what I heard can be found in the Mono & Stereo review of the  Mola Mola Kaluga amplifiers linked below (read the concluding comments);
http://www.monoandstereo.com/2015/08/mola-mola-makua-and-kaluga-review.html

I have no idea whether my impressions are related to the switching frequency George describes, but they could be.  There must be some reason why amplifiers that measure so well do not get me across the goal line with respect to sound quality.
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.
The 6moons review of the Mola Mola Kaluga amps was written by Marja & Henk who were early Hypex adopters,starting with a prototype of the Ncore amplifiers. However, all of us have our biases and no review should be taken as gospel.  As another example, read the rave Stereophile review of the NC1200 based Theta Prometheus amplifiers that Statman replaced with D’Agostino Progression monoblocks, which he likes better.  One thing for sure, the Ncore amplifiers measure very well as pointed out by JA in the measurements section of the review.  

In summary, I do believe the NC1200 amplifiers do many things well and provide a sound quality that many enjoy and  live with.  IMO, they just cannot compete with the better amplifiers I have owned.   
Twenty one people have responded to the OP’s question, Hypex N core module?  

There were many opinions given with some people recommending Brand X and others “very strongly” disagreeing and suggesting Brand Y or Brand Z.  Several posters recommended class A or class A/B amplifiers over class D amps.  Based on my understanding, I did not see any one specific brand, model or technology being recommended by a majority of posters.

I hope these many answers give the OP useful background information and encourage him to demo some models and make his own decision. There is no right answer and what you buy today, you might decide to change next year. A very strange and crazy hobby.

I like my Mola Mola Kaluga class D power amplifiers very much and believe they sound excellent in my situation.  I know that others disagree and that is okay.  
FYI:  Additional interesting back ground material on Class D amplifiers:

http://audiophilereview.com/cd-dac-digital/why-well-soon-be-living-in-a-class-d-world.html

https://forum.audiogon.com/discussions/class-d-is-just-dandy
Yes, I have a lot of experience with the NCore line and build and sell the OEM models.  I also have a lot of experience with the Pascal units and will be getting the new ICE 1200AS in the next week or 2.  Unlike a lot of the companies who build up the NCore line, we do not use the factory wiring which is subpar - the mains are a very small gauge and the input and output wiring leaves a lot to be desired.  All the amps are built custom per order to fit your budget so depending on what you want to pay will dictate the aesthetics of the amp with a focus on fidelity first and foremost.  It has been my experience that most people when given the option do not want to pay the extra few hundred for a "fancy case."  

My opinion on the Hypex amps - totally changed my mind what class D is capable of.  We also build amps that have been compared to the D'Agostino's in A and AB and was heavily biased against class D feeling the only practical use for audiophile purposes was perhaps for a dedicated subwoofer.  I was certainly wrong and the Hypex when built correctly excels in the high and mid register.  In an active system I would use the Hypex NCore for the highs and mid and the Pascal for the low end.  The Pascal is certainly more authoritative and capable of more slam however it doesn't have the same "whimsical" upper register as the Hypex NCore line.  

In regards to the 1200AS line - I will not have my modules until next week and the chipset and topology of the amp is supposedly completely different then the 125AS line...which had some anomalies with it that prevent me from putting into the same class as the NCore based amps.  I will be offering the new ICE modules as kits but have not decided to make an OEM model yet until I get to play with them extensively.  Anything you hear about them now is from marketing teams and folks looking to presell units so I would certainly take anything you hear about them with a grain of salt until the first few weeks into Feb when they are actually in owners hands and broken in and tested.     
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
It is very possible to voice the NCores to emulate other amps.  Just rolling the opamps will change the sound of them as well as various caps and resistors, upgrading to ones like Sparkos makes a huge difference as well.  We have a new buffer/front end coming out that will change a lot of people's opinion on class D products and should have it available in the next 2-3 months.  It will be available as an upgrade to people who purchased the NC500 or NC1200 amps previously.  
Hi
We are Nord Acoustics based in the UK and have sold many Hypex NC500 amps into the states mainly to high end users.

We add our own Nord input board rather than using the standard Hypex one using discrete voltage regulators and Op Amps running in full Class A. The Op Amps are swappable and allow the user to change the sound. A little like tube rolling. This adds texture and depth and delivers a huge soundstage. 

We have one of the longest threads over 1000 pages on US Audioshark forum with many owners comparing our amps to many high end products and have amassed many euphoric feedback comments on our website.
We have even sold some here on Audiogon.

Hope you may find us of interest http://www.nordacoustics.co.uk/
Regards Colin



FIY I understand that the new Marantz PM-10 integrated is based on a nCore500 + SMPS600 monos plus their discrete preamp with linear PSU. Reviews have been great so far.
@noble100
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
Hello noble100, I will try and respond to your question.  First, during my direct comparison of the Acoustic Imagery and Clayton amplifiers over a prolonged period in my system, I did not attribute any performance characteristic or selection bias to the size of the two amplifiers.  In fact, the Acoustic Imagery amplifiers are well-made with very solid CNC'd aluminum casework and excellent Furutech binding posts.  They look cool and between the looks, small size, ability to remain turned-on 24/7, and quiet operation, I truly hoped they would be my last amplifiers.
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?
That is an interesting question.  The Class D Atsahs are revealing, but so are the Claytons.  I did not have the sense that one amplifier displayed more information than the other.  The recorded information was typically Redbook CD burned to a Mac mini and played through Channel D's Pure Music player and then later Redbook CD burned directly to the Antipodes DX.  The DAC is a Metrum Pavane.  Therefore, the material is not high sample rate DSD, or even upsampled to any great degree.  My preference is for a natural sounding presentation so even through the mini I preferred the 24-bit, 88.2 sample rate.  I do not believe the Antipodes upsamples.

I understand your implication that the Atsahs displayed the "warts and all" of poorly recorded material and thus did not sound as good as the Claytons.  I guess I never really thought about that and simply made my choice based on how the two amplifiers sounded in my system with the source I was using.  My issues with the Ncore Atsahs were related to spatial cues and not detail.  I did like listening to music through the Atsahs and particularly liked their rich tone, that not too many SS amplifiers get right IMO.   
noble100 -

You wrote,  "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."

I agree, in my experience the better your system, the more revealing it is of bad recordings. And many, if not most recordings are pretty bad.

My speakers are 4-way hybrids - two 15" dipole bass cabs + mid-horns + bullet horns per side, DSP'd by DEQX processors and powered by eight modified NuForce Class-D amps. My system is accurate and very revealing of poor recordings.

Some of my favorite records sound  pretty bad on my system, in the same way that low-definition movies look sub-par on a high-definition front-projection video system - low def video looks better on low-def TVs. And low-def recordings sound better on lo-def systems.

With excellent hi-def recordings my system shines. No problems with tone or anything else.

I tried using a Yamamoto se45 amp on the horns, and a Pass Labs Aleph, and MacIntosh and Marantz and Fisher tube amps - all were outperformed by my Class D amps.

By the way, I would buy eight Mola Molas or similar if I could afford them - and if they sounded noticeably better than my hot-rodded NuForce I would be surprised.



I really liked my NAD Masters M22 which was based Ncore and most agreed sounded much better than the standard hypex kits, until I did numerous A/B tests in a highly damped room, with reference electronics and Focal Sopra 2's.  The NAD was rendered dry, sterile, and lifeless compared to the good Class AB amps, which was pretty disappointing considering I owned it.

YMMV but I won't be going back to Class D anytime soon after that experience.

i now have a Perla Audio Signature 50 integrated that blows the NAD away in everything but sheer power.
I had followed these class D discussions for a while and wanted badly to try them in my system! I had one of the best class A power amp(Pass Labs) and really like it but size, weight and heat were factors that pushed me for class D! I got Hypex Ncore 500 and for the first time can hear the differences! Ncore is more accurate to PL (might be because I bought PL as 2nd hand and it was old) Ncore has better control on bass and easy to drive any speaker but it is not as musical as PL to my ears specially on low volume ! Long story short, a good class D is amazing for newbies and ppl that don't consider themselves as an audiophile!     
     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
Gentlemen,
If I may provide a designers perspective. I don't want to wade into a he said, she said. I am just providing my design experience.

Class D is going through a maturation stage and developing fast. The prior lack of experience in higher frequencies, above 20kHz, of Audio designers has led to some bad class D designs, while non-audiophiles have entered the market with good designs but bad Audio sound.

Audio sound, aside from being subjective (tubes vs SS), requires real time application and the human ear is very sensitive to sounds not just in the Audio range but outside it as well. Combined they make up the sound. The staging, "air" etc is also made up for many aspects that are not generally measure by Audio designers and manufacturers.

So with that Preamble.
Class D has suffered from lack of high frequency knowledge - designing traces that interacted with each other, designing power supplies that don't have kickback or noise, designing layouts that don't propagate RF, Capacitance in the MOSFETS that  don't allow fast switching (that is turning off from on, and on from off - this is not the switching frequency but speed on which it can respond),  Inductance of the MOSFETS cases, timing of the deadtime vs switch time and so on. While it is not very complex, Class D requires a lot more knowledge AND design then a Class A or Class B or a tube amp, only because there are a lot more complexities to be considered.

A good Class D will keep the dead time to a minimum, reduce interactions between traces and power supply ( overshoot, ring) and have a clean power supply so you don't hear it.   The amp boards and Power supply boards (Switching power supplies) are very sensitive to placement, wiring, components and so on.

Hence just making a amp board that sounds good is not enough. The whole amplifier has to be engineered. Switching frequency, theoretically is nice to have higher, does not work well with MOSFETS, as the capacitance in MOSFETS don't allow for a fast(er) turn off/on. 

The filters can be as clean or as horrible as the designer makes it to be. Having a sharp filter on paper with lossy components makes for bad sound as lossy components have a lot of parasitic impedance and will change the whole curve and filter.

Finally the Class D amps are of age where they can be superior to any other class available today - it just takes good design. Class D has many benefits that you cannot get from the other types of amps, including better sound. 

BUT as all things, there are no absolutes. It must be better design, better built, better implemented, better engineered to be better. Just saying Class D is better or worse does not make any sense as saying Tubes or SS is better then the other.

Hope that helps a bit with the understanding of Class D
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  

    
Anybody have experience with Nord Audio N-core power
amplifier ? The use own buffer module https://www.nordacoustics.co.uk/products 
and say the  Using Nord Input Buffer Boards (Full Specifications and Op Amp Sound) with high end discrete Sparkos Labs Voltage Regulators and a choice of Sparkos Labs SS3602 or the Sonic Imagery 994 discrete Op Amps both run in full Class A. And offers a richer, warmer, tonally dense musical sound with greater sound stage while maintaining all the benefits of the standard amp. Superb bass control with sweet high resolution mids and treble.
In what would be considered a "relatively affordable price range"...what is that then differentiates the Nord Acoustics from a PS Audio Stellar 300 from a Merrill Audio Taranas from a Benchmark ABH2 as they all have been given accolades for great sound at less than the price of a small car??
@snapsc 
 
Check all prices on Nord site, the multiply 1.3  plus  $ 100 shipping
and VAT  , it may be custom charge, 
PS Audio Stellar 300 is not Hypex N-Core , the get MOSFET output
stage,   Benchmark ABH2 is Class D , but dont mention which
module they used , i think no N-core.Just only Taranas  from Merill use
N-core, The sound excellent 
@merrillaudio +1

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.
This statement is false. The filter can do its job properly at current frequencies. There is an advantage to going to faster switching frequencies- lower distortion. But by switching faster, you either have to have faster and more expensive output devices and deadtime to allow the outputs to switch. Deadtime increases distortion. So there's a bit of a carrot that is being chased.

@merrillaudio  would you be interested in a circuit that bypasses the need for deadtime?
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
mitch2
I have no idea whether my impressions are related to the switching frequency George describes, but they could be. I owned and used in my main system a pair of the Acoustic Imagery Atsah monoblocks made from Bruno Putzeys' highly rated Ncore NC1200 amplifier and power modules. In summary, I sold them after a prolonged, direct comparison with three other Class A and AB amplifiers.
IMO, they just cannot compete with the better amplifiers I have owned.     


statman
I will try and explain my experience. I was happy with my Theta Prometheus monoblocks. I must add that I am much happier with my D’Agostino Progression monoblocks



It's not the Class-D switching frequency itself so much, but the low order filter that's needed that has to get rid of it.
  
If that filter could be much steeper then it's filtering, then it would work and not have any affects into the audio band, and maybe compete with good linear amps. But it can't be a steep filter, because it has to handle the full power of the amp and would burn out very easily.

So the only thing is to make the switching frequency at least three times higher, then that filter can do it's job properly and not have or leave any effects down into the audio band.

The designer of Soulution amps and many other hi-end amps are of the same opinion.

 Cyrill Hammer (Souloution) 
"if you want to have your product performing at the cutting edge it is not possible with today’s known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz."

Lew Johnson (Conrad Johnson)
"I tend to think that Class D circuit design is an approach best relegated to producing low-cost, physically manageable multichannel amplifiers—where one might accept some compromise in sound quality for the sake of squeezing five, six, or seven 100 watt channels into one moderate-sized package for a budget home-theater installation."

And there are many others if you care to search.
You'll see many "old school" linear amp manufacturers starting to do Class-D just to stay afloat, as they are having an economic effect with those businesses, that can't weather the storm and wait for Class-D to get better with future higher switching frequencies. 

Cheers George

    
The filter can do its job properly at current frequencies. There is an advantage to going to faster switching frequencies- lower distortion.

Sorry this is not correct, that is why when Stereophile do their bench tests they have to use a very special low power external steep filter on the output to get some good looking measurements from them.

Stereophiles: Audio Precision’s auxiliary AUX-0025 passive low-pass low power filter.

Trouble is that filter can’t be used at listening levels, as it would burn up in an instant.

Cheers George
If you look at the specs for a Merrill tarranis which uses an ncore module for class d output they show bandwidth to 50 kHz. If you look at the ps audio stellar 300 which uses an ice module and bandwidth to 50khz. The benchmark ahb2 is shown as a class ab/h not class d but class d efficiency and bandwidth shown to 200 kHz. The first watt f7 class a with bandwidth shown to 100k. All of these Amps are well regarded and carry the designers name and therefore affect his reputation. Is it possible that the difference is the difference in the voicing.... sonic signature that each designer intends based on their hearing and memory of music??
"if you want to have your product performing at the cutting edge it is not possible with today’s known switching technologies. In order to come close to the performance of the best linear design we would need high-current semiconductors that provide switching frequencies of several MHz or even GHz."
Several MHz isn't a problem. We're working with inexpensive devices that can easily do 5MHz and beyond. The problem is deadtime. That has so far proven to be the switching limit; that's why they don't switch much higher than maybe 2-5MHz tops. The deadtime increases distortion, and the faster you switch, the more you need it- so there is a minimum distortion that you can hit, sort of like Whack-A-Mole. I did state this in my previous post.

When you are switching that fast though, the speaker itself is part of the filter; there's no problem getting a filter to work and it won't burn up.



Here are the 10khz waves of Class-D both done by Stereophile tests, one with and one without the Stereophiles special AUX-0025 passive low-pass low power filter.  This filter can't be used while listening as it would burn out almost instantly.

With the special bench test filter:
https://www.stereophile.com/images/916BC600fig2.jpg

Without the special bench test filter:
https://www.stereophile.com/images/1212AM1fig02.jpg

Now I ask ANY linear amp manufacturer, would they be happy if their amp gave a 10khz square wave that looked like the second pic to sell to the public.

Cheers George   
Several MHz isn't a problem. We're working with inexpensive devices that can easily do 5MHz and beyond.

Technics have produced a Class-D amp (SE-R1) that has double today's switching frequency speed so the output filter has less of a chore to filter it all out, but it's $30k usd and special order only if your the God or Emperor of Japan?

This amp is half the way there because of the special hi speed semiconductors used to get double the switching frequency of 1.3mhZ

It's getting there, but needs to be double d again.

Here is one reviewers take on the Technics Reference SE-R1 Class-D amp:

" No other audio system that’s graced our listening room here at DT has captivated and mesmerised our staff quite like Technics Reference system. Seriously, some of us are having trouble getting our jobs done because we can’t peel ourselves away. This is the sort of audio system that you must hear to understand. Listening to tracks that we’ve heard 100s of times — and on excellent systems at that — is now a revelation of once hidden nuance and detail. Not only are we hearing things we’d never heard before, we’re hearing it in a way we’ve never heard it before."  

Cheers George   

Here is an example of today’s switching frequency trying to be filtered by Mark Levinson No.53 with the $50k usd Class-D. They tried very hard by as you can see by the 4 massive x filter chokes added together (paralleled or series or both) to give a steeper filtering effect on the switching frequency, it worked as the 10khZ square wave shows, without the use of Stereophiles AUX-0025 passive low-pass low power filter, but adding filters together is well known to create other problems, this amp it seems was not a success for ML.

" However, the more I listened, the more the overall sonic picture seemed flat and uninvolving. An enigma.—John Atkinson"

ML Class-D monoblock x1 showing 4 x filter chokes.
https://i.pinimg.com/originals/f1/c5/3a/f1c53a9e8f03bd1ea3a4ed38f65c0b1e.jpg

ML Class-D 10khz square wave without Stereophiles special testing filter.
As you can see very acceptable for Class-D with no switching frequency ringing getting through those filters.
https://www.stereophile.com/images/1212ML53fig02.jpg

Cheers George






I completely agree that switching frequencies have to be increased!

But, the problem is not switching speed! The problem is how long it takes for the device to turn on and off, which is different. Because that takes some time, the circuit has to wait until the device has changed state before the other device can do its thing. That waiting time is deadtime, which increases distortion.

**That** is why you go with faster and more expensive devices; its all about keeping deadtime to a minimum.

Put another way, with conventional class D circuits, a switching device that can do 10MHz can only be used at a few hundred KHz before deadtime becomes the big impediment.

Now the parts we work with are not that expensive, but we found a way to eliminate deadtime. This allow us to switch at much higher frequencies.
Now the parts we work with are not that expensive, but we found a way to eliminate deadtime. This allow us to switch at much higher frequencies.

Ralph, what is the approx ringing of the square wave I linked to in the 1st pic, it is the switching frequency noise

Yes dead time is another problem.
But you will still have the problem, of eradicating the switching noise completely with the output filter without ANY effect on the audio band from 20hz to 20khz. So say a 10k square wave will look like the ML’s one I linked to above, without any Stereophile external bench filters used.

BTW I wish you luck on your Class-D quest, but Technics has shown the way with limited supply of the transistors they use. In the future there maybe a good supply to everyone with hopefully 3 x the speed of switching frequency. But i suggest not to jump on the gravy train just yet, wait for the technology to catch up, or the end maybe like the ML53.

Cheers George