Which Class D Amplifier? PS Audio, Ghent, Nord, Merrill or other???


I’m looking for a new amp & want Class D.

I’ve seen various brands mentioned, such as PS Audio, Ghent, Nord, Merrel to name a few, but I’ve not heard any of them.

Which company is producing the best sounding Class D?
Which models should I be looking to demo?


Thanks



singintheblues

Showing 50 responses by noble100

singintheblues,

     The use of GaN semiconductors in class D amps, despite georgehifi's repeated claims to the contrary, currently have not been established as providing definitively superior sound quality to the technology and semiconductors employed in the better class D amps available on the market today (typically Field Effect Transistors referred to as FETs).

      As you learn more about how class D amplification actually works, you'll understand why reduced dead-time and higher switching frequencies have the theoretical potential to improve performance. 

      From my understanding, however, it seems that the GaN semiconductors reducing the dead-time has a greater potential of improving sound quality than higher switching frequencies do.  I believe this because faster semiconductors would reduce dead-time which would result in reduced distortion and likely better sound quality.

       The need for higher switching frequencies in class D amps is usually based on the theory that current frequencies are too low and cause sound anomalies in the human audible range of 20- 20,000 Hz.  Current class D switching frequencies are typically in the 400-600 KHz range with theory proponents claiming switching frequencies above about 1.5 MHz are required to ensure there are no sonic anomalies in the audible range.

     However, this theory has never been scientifically proven and there's virtually no evidence to support it.  Several class D amp designers. including the highly respected inventor of Hypex NCore Bruno Putzeys, have publicly stated there's no need for increasing the switching frequencies  above current levels. 

                  
     For some unknown reason, georgehifi has continued to disregard the lack of evidence and has remained one of the very few people still stubbornly clinging to this unsupported theory.  Perhaps, in the spirit of keeping an open mind, it will be discovered that only a select few individuals are capable of hearing these supposed sonic anomalies but that's a bit of a stretch.

     I'm a big fan of class D amps and have replaced all of my previous class AB amps with them.  The class D amps in my combo music and HT system (ClassD Audio and Emerald Physics stereo amps and D-Sonic mono blocks) are smaller, lighter, run cooler, use much less electricity and sound much better than my old amps in all important criteria I care about.  Highly recommended.

     I definitely don't think there's a need to wait for GaN semiconductor technology to 'trickle down'.  As I believe you've already discovered, good class D performs exceptionally well.  If you're not afflicted with hearing sonic anomalies either, why wait?  Perfection can be the enemy of the extremely good.
   
      As far as good class D suggestions for you, I'm willing to offer a few brands/models to consider but would prefer knowing more about your system, needs and budget first.  

Enjoy,
 Tim
     
      
        
 
georgehifi,

     I stated the GaN technology will reduce dead-time and likely result in even better class D sound quality.  I believe this could be a significant step forward even though I have yet to hear an amp using them.  My main point being current good class D amps sound so great, why wait for perfection? 
     Class D amps utilizing current technology will not suddenly become worthless just because possibly even better class D amps are available.  How low current amps would drop in value relative to new GaN amps is likely to be a function of the actual sound quality and price variances between them.
     I do agree with you on the importance of the quality of the filters used in class D amps that removes the carrier switching frequency from the audio signal prior to amplification.  I believe improvements in these filters  probably has more potential to improve the quality of class D than raising the switching frequencies would have.  I was going to edit in some comments into my last post about the filters but realized my omission a bit too late.
       I don't perceive any sonic anomalies at all in any class D amp I own or have ever listened to.  Perhaps I'm just lucky or maybe it's just that no sonic anomalies in the audible range exist.
     I think not buying a current class D amp because the semiconductors are not yet perfected is akin to not buying a 427 Corvette in the 1960s because the fuel injection wasn't yet perfected.  In either case, you're just denying yourself the enjoyment of the extremely good due to a lack of perfection. 
    But experiencing the enjoyment of good class D is currently more important to me.  If I enjoy the sound of new class D amps utilizing GaN semiconductors or a higher switching frequencies more in the future, I'll probably buy a few if the price is reasonable.  I'll offer my current class D amps to both my sons at good prices.
     I'm also eager to see and hear Ralph's upcoming class D amp

Later,
 Tim

     
     To date, I've used 3 different class D amps on my fairly inefficient and older Magnepan 2.7QR speakers (87db @1 watt):

ClassD Audio SDS-CS440 stereo amp. 44O W/CH at 4 ohms.

Emerald Physics EP-100.2SE stereo amp.  150 W/CH at 4 ohms.

D-Sonic M600 M3-600M mono block amps.  1,200 W/CH at 4 ohms.

     All drove my speakers well, have a decidedly neutral and accurate sound quality with noticebly better bass response and dynamics than my prior and decent quality class AB amps (McCormack and Aragon). 
     I'm currently using the D-Sonic on them because they sound the best to me due to the superior 3-D sound staging, life-like dynamic impact, tonal balance and the overall sense that you are at the venue or the musicians are in my room.  
      D-Sonic has replaced the M3-600M monos with their M3a-600M model which the owner, Dennis Deacon, stated now utilizes newer  Pascal class D modules instead of the original's Abletec/Anaview modules for what he described as a subtle improvement. 
     I've listened to the Bel Canto Design Ref600M amps in a friend's system and they are also very good with an overall sound quality that's very similar to the original D-Sonic.
     Please list your system, needs and budget for more specific suggestions.
Thanx,
  Tim  
redrocket,

    wolf's thread contribution is requesting you should afflict yourself with Monkey Plaque prior to discussing so that your comments are well informed and relevant.

Please afflict yourself and report back to us.

Thank you in advance for your cooperation,
    Tim
Hello tweak1,

    You stated:
" noble/Tim

FYI: I had 2 EP 100.2SEs (with upgraded fuses) for well over a year. I got the bug and bought a Audio Alchemy DPA-1 stereo amp. It is much richer in the midrange and bass, deeper and more holographic sound stage= much closer to real music."

     Good to know, I'm always interested in learning about other good class D amps.  Thanks.
     I currently use my EP 100.2SE in bridged mode to power my Magnepan CC3 center channel speaker and my ClassD Audio unit in stereo mode to power my rear surrounds for HT usage.  I have no current complaints but I'm always open to upgrades in performance. Lots of very good class D options now available that I'd like to audition.

Thanx,
  Tim 
Slimpikins5 stated:
"Fast forward: I was further piqued now about Class D and wanted to get into something much more advanced, so I picked up a pair of Anthem Statement M1 Class D mono blocks which run around $7K for the pair. These babies put out 2000 watts per channel at 4 ohms (my speakers) and all I can say is; holy moly I was blown away at how much better they play than the Class A/AB amp I have been using!   Far more dynamic range, better soundstage and imaging, no high frequency harshness at all, just super clean floor shaking output."


     I find your description of the improvements you hear from your Anthem Statement M1 class D amps,  "far more dynamic range, better soundstage and imaging, no high frequency harshness at all, just super clean floor shaking output",  to be very similar to the improvements I've experienced upgrading to the D-Sonic M3-600-M class D monoblocks.   
     I just wanted to add a few additional comments about my experiences for the benefit of readers who haven't yet listened to a good class D amp in their systems.  I suspect my comments will ring true to all owners of good class D amps, also.
      I was initially struck by how quiet these amps are.  Music just seems to emerge from a dead silent background with absolutely no background noise that is verified by their excellent Signal to Noise Ratio measurements.  I believe this, along with extremely low distortion measurement levels, combines to result in an exceptionally detailed and transparent overall presentation that also allows for a sound stage illusion that is remarkably 3 dimensional and stable ('in the room' sensation on well recorded tracks). 
     Another quality that is quite obvious upon first listen is the overall neutral presentation.  I was actually a bit concerned about this quality since I thought I preferred a more flavored sound tilted to the warm side of the spectrum.  I had used a VTL 2.5 tube preamp (with NOS Mullard tubes swapped in) expressly for this purpose in my system for years.  After careful comparison with and without the tubes in my newly class D amplified system, however, I discovered my music sounded just as sweet and without any hint of harshness without the tubes. 
     I thought my tubed VTL would always be in my system and I had even  just bought an expensive quartet of replacement NOS Mullard tubes for it.  But I felt I had to trust my ears, so I sold my beloved VTL to a buddy and have no regrets.
     I think the above descriptions by slimpikins5 and myself are a good summary of what to expect from a good quality class D amp.  Just remember that there arevariances in the performance quality of class D amps just like all other amp types so try to audition any candidates in your system prior to deciding. 
     But I'd still prefer to know your needs, system and budget before offering specific amp suggestions. 

Tim
     
byington711,

     If you're still following this thread I have a question:
    From your 1/4/19 post on this thread, I'm not sure if you own the stereo PS Audio BHK 250 or the mono block 300 amps in your system.   
     Regardless, it's my understanding that the PS Audio BHK 250 stereo and 300 monos are class AB amps, not class D amps. 
      Therefore, neither have the usual class D benefits of compact size, low weight, low operating temperature and low electricity consumption,  Both of these amps are quite large (at least 17.1"W x 8.7"H x 14"D), quite heavy (83-100lbs), have high operating temperatures  and consume considerable electricity (at least 175w @ idle and 850/1.600w @ full power at 8/4 ohms). 
     By listing and suggesting these amps on a thread titled :Which class D amp?....", my concern is that some might mistakenly believe that the PS Audio BHK amps actually are class D.
      Can you please clarify and definitively confirm the PS Audio BHK areps are both class AB?

Thanks,
   Tim
georgehifi stated:
     " Amps are adjusted and calibrated at the factory for peak performance after a short 1/2-1 hr warm when they've reached operating temperature, even tubes, to say they sound better after hours and hours is a furphy."

furphy?

      Please take our official multiple choice quiz on this weird word's meaning:

A. furphy: An Australian English slang word meaning an erroneous or improbable story that is claimed to be true.

B. furphy: An Australian English slang word describing the sound a down-under cat makes when attempting to cough up a fur ball.

C. furphy: An Australian slang word, only permitted to be utilized in emails but forbidden to be ever spoken aloud and exclusively used by members of a certain Australian political fan club, that members claim translates to American English as 'covfefe'.

D. furphy: How an Australian pronounces the word 'thirsty' after downing 2 gallons of Foster's beer.

     Correct entries may or may not be eligible to win an official Aussie Georgehifi Furry Fluffy Furphy Action Figure that performs Frequent Forward Flips, unofficially but commonly also known down-under as an OAGFFFAFFF  just for fun.

Batteries not included,
Tim
     Okay, I just wanted to add a comment to my previous post to agree with other posters (that only appeared to me and I read after I posted) that potential lightning strikes are an extremely legitimate reason to unplug your amps and components.
Thanks,
   Tim

     Concerning whether class D amp performance improves by leaving them constantly on 24/7, I tend to agree with erik_squires that there are sonic benefits.
     I initially turned all of my class D amps(2 stereo and a pair of monos all with linear toroidal power supplies) off each night, with amp off/down times varying between about 6 to 20 hrs/each.  It was fairly obvious to me that my class D amps required some warm-up span of time to reach their optimum performance levels once they had been turned off for 6-20 hrs. 

How long did they take to warm-up? 
I didn't record time trials but I subjectively recall a time range between about 15 minutes and an hour.
       After a few weeks, I then began just leaving them on 24/7 and I could clearly hear my amps remained at a optimally warmed-up performance level.right from the get-go.
     For accuracy sake, it should be noted that my perceptions of when my class D amps are optimally warmed-up is a subjective measurement based on my ears and amps so YMMV.
     I should also state that, even if this warm-up period of my amps was proven to me to be a 'placebo affect', I would continue to leave them on 24/7 simply due to the impressive simplicity and convenience  factors.
     The main point I want to make, however, is concerning the statements from slimpikins and georgehifi of " As far as warm up is concerned, I cannot hear any differences in a cold start up vs. the amp having been on for 4 hours... other than Bourbon has taken over and everything in the room is just better." 
     Besides this statement being mildly humorous, I'm not sure these gentlemen understand that their agreed upon confession logically leads to only one conclusion of leaving class D amps on 24/7.   
     Since turning class D amps off would result in insignificant electricity and monetary savings, and since both of these individuals are admittedly unable to discern the sonic differences between cold and optimally warmed-up class D amps, why would they not just leave these amps on 24/7 and gain/enjoy the dual benefits of simplicity and convenience?  
     Do they have a phobia of a highly unlikely fire?
     Are they overly sensitive to the minute levels of heat produced by idling class D amps?
     Are they adverse to the simplicity and convenience of having their amps perpetually and immediately operating at the first inputted source signals?
     Are they being overly argumentative due to personal biases against the current large crop of good class D amps because they're not yet perfected?
     I really don't understand.

Tim


     teo_audio stated:

" The human ear is capable of decoding intermixed harmonics and timing cues into the 200khz plus ---with zero jitter. Micro and macro signals intermixed. With two ears doing this as a combined spaced pair, with the micro and macro intermixed temporal cues."

Hello teo,
     
     Are you certain this is true?  I've never heard or read this claim before and I'm very interested in reading about any research you know of on this subject. 
     Contrary to your apparent opinion, I am very interested in the subject of human hearing and how the brain processes the signals from our ears and determines how we perceive these inputted signals. 
      I believe the understanding of the ear-brain relationship, along with the understanding of room acoustics, are critically important in explaining how a solid, stable and 3-dimensional sound-stage illusion is able to be created in a room utilizing just 2 properly position speakers.
     My understanding is that humans cannot detect frequencies above approximately 20,000 Hz, which I believe is mainly based on early 20th century empirical research. In fact,  audio recording and playback equipment since this time has been designed and built based on this upper frequency limit.
     Before I go any further, however, I'll wait for your reply just in case I'm misunderstanding  something in your statement: " The human ear is capable of decoding intermixed harmonics and timing cues into the 200khz plus ---with zero jitter."

Thanx,
  Tim


I know I am, and believe most class D amp proponents on this thread are, very open minded toward further potential advancements such as the newer GaN FETs, improvements in the filters used to remove the carrier frequency prior to amplification and even the as of yet unproven benefit of MHz-plus signal carrier frequencies.

     With the extremely high quality performance levels of such a large number of class D amps using just currently available technology, significant future improvements in class D amp performance levels is difficult for me to imagine. I honestly cannot identify any aspect of my good quality D-Sonic M3-600-M class D amps’ performance that I would characterize as deficient.

     As an experienced user and proponent of good class D amplification, I have no choice but to consider claims of class D harshness and sonic anomalies in the midrange and treble as illegitimate, view those claiming such with great skepticism and suspect them of having ulterior motives.

     I state this based on my own experiences using multiple class D amps in my system for about 4 yrs, the complete lack of evidence that current signal carrier frequencies in the 400-600 KHz range affect frequencies in the audible range, anecdotal claims of class D upper frequency harshness being based on early class D amps and very rarely on the newer good quality amps and my complete inability to detect any sonic anomalies or upper frequency harshness. If you can’t perceive any sonic issues then you have no sonic issues, right?

     To be fair and empathetic to those who honestly hear sonic anomalies in good quality class D amps that I and many others have never detected, perhaps future research will discover that these anomalies do actually exist but only some individuals are able to detect them.

     If this is the case, that is an affliction that I wouldn’t wish on georgehifi, because listening to music through good class D amps is really quite spectacular when you’re not afflicted with this horrific condition.

     Just really bad dumb luck. I hope the GaN FETs and/or higher switching frequencies will eliminate or at least ease the suffering of all those afflicted with this horrendous and inhumane potential explanatory condition.

Best wishes,
Tim



singtheblues,
     If you want specific recommendations, you still need to let us know your budget, the rest of your system any other requirements.    Even a dollar range will do. 
     You need to throw us a bone, here for good suggestions.  There are a wide variety of good class D amps at a wide range of price points.  I consider under $1K as low priced, $1 to about $8K as mid priced and over about $8K as high priced (all prices $USD)
      My opinion is that you're best option is to choose amps that allow in-home trial periods of a few weeks so you can return them, no questions asked, for a full refund if you don't like them.

Later,
  Tim     
     
Hello georgehifi,

     The AGD mono amps you linked a review to look very interesting. 

   https://positive-feedback.com/reviews/hardware-reviews/agd-production-vivace-gantube-monoblock-ampli...

      So, it sounds to me like you were right on the money about how these new GaN transistors ability to positively affect the sound quality of class D amps. The reviewer stated these amps "sound like a SET tube amp but with better dynamics and breadth". 
      If true, that is an amp sound signature that could be revolutionary since.I believe it's the first of its kind.  I've never heard of an amp described as combining SET tube sound with better dynamics and breadth.  
     Of course, there's more than transistors that determines the sound qualities of an amp, right?    Or could we be stuck thinking conventionally about a new technology that could prove to be game changing? Most of us are accustom to discussing the sound differences between amps that use FETs and Bi-Polar transistors, with a total lack of knowledge about the affects of using the new GaN transistors.  
     All I know about these new GaN transistors is that they are significantly faster switching from on to off, and vice versa, which thus significantly reduces dead-time (the down time when a transistor is neither on nor off but in an in between idle state) that ultimately results in lower distortion. Lower distortion is always a good thing but could there be other forces at work that could result in improved performance?
    Currently, I have no answers to my own questions. I'm just thinking out loud and hoping you guys n gals will pitch in and help.
    I find this new GaN transistor technology very exciting but want to keep it in perspective.  I hope their use continues to trickle down to even more affordable amps as George predicted (good call).  It seems they rather quickly went from only being used in the $50K Technics to these new AGD monos at $15K/pair. Still too steep for me but I can wait..

Thanks,
  Tim     
    

It’s my understanding that there are currently 2 leading producers of high-speed GaN power transistors, EPC and GaN Systems.
Does anyone know if there are differences between the two of them and whether GaN Systems has a proprietary patent on their GaN FET transistor, too?

Are there other producers of currently available GaN transistors with unique patents?

Are there other producers of currently available high-speed GaN FET drivers besides Peregrine and their PE29102 driver?

I’m just trying to better understand the companies and products involved in these emerging markets.

Thanks,
Tim






    " that I completely fail to detect any of the sonic shortcomings that georgehifi claims exist on my amps due to traditional FET transistors, the switching frequency being too low and the filter used to remove this switching frequency being of poor quality."  

Hi mapman,

     This quote from one of georgehifi's previous posts is actually my words from a post that has since been deleted by a moderator for some unknown reason.
      I was referring to georgehifi's frequent comments criticizing good class D amps, which I consider myself to be a user of,  as all having sonic shortcomings due to using traditional slower FET transistors, the switching frequencies being too low and poor quality filters used to remove these signal carrier frequencies.  My point being my total failure to detect any sonic shortcomings in any of my 3 good quality class D amps despite his persistent claims that these shortcomings exist.

   Nevertheless, I believe the questions from your last post, directed at georgehifi, remain very relevant questions:
 
  George what specific amp or amps are you referring to in regards to "sonic shortcomings"? Two or 3 examples will do if you could.

Also what amp or amps specifically are you comparing with to reach that conclusion? What were the shortcomings of those?

Are you comparing apples/apples in terms of cost?  

What are your reference recordings used to make the assessment?

Just to be clear I’m asking what you have specifically heard, not what you deduce from other sources.

Being a technical guy, I’m sure you can appreciate the value of being specific and not making generalized statements based on a limited sample.
     Georgehifi has consistently refused to answer all questions about his claims of sonic shortcomings in recent class D amps in general.  He's failed to respond to requests to elaborate and be more specific on his claims of sonic shortcomings from myself, several others and now from yourself.
     Based on georgehifi's numerous responding posts on many class D threads, it's fairly obvious to me that he has little to no experience actually listening to good quality class D amps.  
    I say this not only because his descriptions of what these claimed sonic shortcomings sound like are very vague but also on his obvious inability, and often just refusals to respond to requests, to be more specific in his descriptions of what these sonic shortcomings actually sound like.
      Because of the above, the complete lack of supporting evidence of his claims from any source  and my and others' complete failure to detect these sonic shortcomings in any of our good quality class D amps, I've reached the baffling conclusion that he's fabricated his claims of sonic shortcomings for some unknown reason.
      Although he frequently states he'll buy class D amps once they are perfected, I now consider this an attempt to disguise his true prejudices against class D and possible ulterior motives for his statements, unsupported theories and comments.

Tim


     
 



 
Hello georgehifi,

     I can not only handle the truth, I respect it and have a habit of speaking it. Can you claim the same?
     It is true that you did post about the newer GaN technology a while ago and their potential beneficial potential for audio amps and I found it very interesting and promising.  Thank you.
     I have no issues with you touting the potential benefits of faster switching GaN transistors that would result in reduced dead-time and reduced distortion.  GaN transistor technology is a few years old and their potential for improved solid-state audio amp performance are well understood and mainly agreed upon.
      My main issue with you concerns your claim/theory that current class D carrier frequencies are too low and result in sonic shortcomings in the audible range. Unlike GaN technology, the potential benefits of higher switching frequencies for improved class D amp performance have not been researched and, therefore, are not well understood or agreed upon.  The truth is that It also has never been proven that current level switching frequencies are too low and result in any sonic shortcomings in the audible range.
     Yet, you seem to believe it's just a matter of opinion as to whether these sonic shortcomings exist in the audible range. I believe this has yet to be decided empirically.
      My take on this issue is a bit involved but not really complex.
      My reasoning is that,if your theory of sonic shortcomings in the audible range are someday proven to be  false, then that nicely explains why I and many other users of good class D amps have failed to hear them since they don't exist.
       If your theory of sonic shortcomings in the audible range are someday proven to be true, however, then that would verify their existence but present a whole new issue of why I and many other users of good class D amps are unable to discern these now proven sonic shortcomings. 
      I.can state with absolute certainty that I cannot discern any sonic shortcomings on any of my 3 good quality class D amps that all have switching frequencies in the 600 KHz range. 
     If your theory is someday proven to be true and sonic shortcomings actually do exist in the audible range due to the switchng frequency being too low, I'd be very concerned about why I wasn't able to discern these now proven sonic shortcomings.
     I'm now 60 and have never considered myself  to be a 'golden ears',  But I believe I still have good hearing, I'm able to discern the differences between various power cords and interconnect cables I've compared on my class D amps and think I'd be able to hear any sonic shortcomings on my system if they existed.
     After I initially read of your theory concerning the switching frequencies on class D amps being too low and being audible, I was a bit alarmed because I could not hear any sonic anomalies on my class D system.  So, I spent most of a Saturday listening to my system trying to detect any sonic shortcomings in the midrange and treble but failed to identify even a hint of any sonic anomalies.
     Ultimately, I had no choice but to conclude that no sonic shortcomings existed on my class D system.  The only other possible conclusion is that I, for some unknown reason, am incapable of perceiving these sonic shortcomings.  But I consider this a bit of stretch with the current lack of research supporting this premise.
       
    So, I'm going with the conclusion that these supposed class D sonic shortcomings don't actually exist until proven otherwise.  

 Tim
slimpikins5,

     I don't think I've degraded to nasty commentary toward georgehifi in my posts.  I think he has the right to say anything he wants.
    After all, this is an audio forum everybody.  One member posts a question or statement and the other members respond.  Truthfulness and good/accurate info are important, politeness not so much.  Ruffling a few feathers is not a big deal, people.  Everyone deserves a tune-up every so often.  
    I'm originally from Chicago, and a punch to the face there is just considered a suggestion that you may want to reconsider your position or, perhaps,  rephrase it.  No big deal and you're always free to punch back as long as you politely say "I beg to differ" immediately beforehand.  No moderators required.

Erik,

     Just like you, I'm completely satisfied with my combo ht and music system utilizing all class D amplification.  Georgehifi's comments about class D amp shortcomings don't really bother me because I don't hear any of his supposed shortcomings in my class D amps, either.  If we don't perceive any of his shortcomings, they don't exist, right? 
Later,
Tim    
Mapman: " Also I do not hear the issues George claims even at this modest cost."

Reports from those who do hear issues, with class D or T, are scarce. Rumor has it that georgehifi’s real father is an Australian sheep dog, perhaps he can hear dog whistles, too.
I’m still waiting to learn from georgehifi exactly what these supposed class D sonic shortcomings actually sound like. His very rare previous descriptions were so vague that they’re meaningless.
Has anyone else claimed to hear these issues besides him? I don’t recall anyone else chiming in to claim they hear issues with class D. I faintly recall a single poster, who didn’t have a user name of georgehifi, claiming they listened to some D amps stating that ’something was missing’ or ’it lacked soul’ but nothing specific that could be relied upon with any confidence nor even be considered a corroborating anecdotal description since I believe this was claimed only by a single poster.

Tim
Hello Michael,,

     Very nice post with some very interesting information and thoughts from a system tuner's perspective.
     As a layman, I think it's an important reminder that designing and engineering a good sounding audio amp, regardless of type, requires making many good smaller decisions (based on one's knowledge, experience and goals) all contributing to the final amp creation's sound.
     Designing very good class D amps seems to be especially difficult since amp designers must make decisions based not only on their acquired experience and knowledge of traditional amp design but also must gain experience and knowledge of how to incorporate the newer and higher performing component parts into their designs.
Thank you,
   Tim
Hello tweak1,

      It seems you've discovered another benefit of class D amps that I don't think has been mentioned thus far in this thread: good examples of class D amps are basically a 'straight wire with gain ', which is numerous experts' definition of an ideal amp.
     Distortion and the noise floor are measurably so extremely low that it results in nothing being added or subtracted from the inputted signal. This causes the overall presentation to be very detailed and neutral.
      The benefit of these qualities is that it allows users to much more easily discern the affects of different power cords, interconnects and spkr wires on your system's overall sound. With my prior good quality class AB amps (Adcom, McCormack and Aragon) I thought I could discern subtle differences but, in retrospect, there may have been some placebo effect occurring.  With the good quality class D amps, the subtle differences were discerned much more easily.
     On a larger scale, the clarity and honesty of good class D amps will also allow you to much more easily discern weak links in your system such as upstream components and source recordings. 
      I had always thought I preferred a warm overall system sound.  For about 5 years previously, I used a tube preamp (VTL 2.5 with NOS Mullard tubes swapped in) paired with solid-state amps to achieve this warmth.  After comparing the overall sound with and without the tubes, however, I found most of my favorite recorded source music sounded just as sweet to me without the tubes.  So I sold my VTL and a set of 4 just purchased NOS Mullards to a good friend and have not regretted it since.
     This same clarity and honesty also applies to recorded music sources.  There's no masking or coloring of the signal so recordings that sounded good to on previous amps may not sound as good using good class D amps.  The recordings are just faithfully reproduced with warts and all.  Bad recordings will sound like it and good recordings will sound especially good, the differences being obvious,
     .I discovered my CD collection consisted of mainly good recordings with just a few clunkers (for some reason my Cold Play CDs sounded much worse but still good in my car system). 
     Just after swapping out my class AB amps for class D, I also added a computer audio setup; consisting of my laptop running JRiver Media Center, a Synology NAS and using my Oppo 105 as a DAC/Player.  I ripped my entire CD collection to the NAS and began downloading some high resolution 24 Bit/96KHz music files ,too. 
     All the CDs sound very good but the music recorded direct to hi-res 24/96 sounds incredibly good; by a wide margin the best I've ever heard on my system with solid/stable 3D sound stage and the large dynamics I only previously experienced with live music.
     My main cautionary message is that class D amps may not suit everyone's  tastes or system.  For example, those that don't have the funds to upgrade upstream components that may suddenly sound deficient.  Or those who prefer a more colored system sound and don't want a very detailed presentation that will reveal the true quality of all of your recordings.  
     However, users of good class D amps are still able to tailor the sound of their system sound via the choice of preamp used.  The amp will just faithfully amplify the outputted preamp signal so it's critical that the preamp outputs the desired sound qualities.  

Hope this helped a bit,
  Tim
     
     

     The EPC eGaN FETs switch 10x faster than silicon MOSFETs and have zero stored charge.  I'm guessing that probably improves sound quality when used in a class D amp.
.
  Elegant Audio Solutions in Austin, Texas, created a class D amplifier (200 w at 8 ohms and 400 w at 4 ohms) using the EPC eGaN FETs with THD+N as low as 0.0005% and very low feedback. Moreover, this is done without the need for a heat sink and eGaN-based amplifier can plug directly into the standard amplifier implementation of many existing systems. I'm very interested in auditioning this amp in my system. 
Here's a link to the amp photo:

https://www.planetanalog.com/author.asp?section_id=3065&doc_id=564363&image_number=4

     Anyone want to volunteer to make me a pair of mono blocks using a couple of these amps placed in nice aluminum chassis with XLR inputs, IEC jack and rocker ON/OFF switch on the back and a single blue power status LED on the front?

Thanx,
  Tim




Hello georgehifi,

     Thanks for the link to the EAS™ eGaNAMP2016 amp module.
I’m a bit confused, is this an EPC or EAS class D amp module? Or is EAS just using a standard EPC module for their amp?

     I was assuming that EAS built a proprietary module using EPC eGaN FETs using either an EPC or Peregrine driver but I'm not certain.
     I was also assuming EAS intended to sell their modules to OEM amp manufacturers and not to individuals for diy amps since no prices are listed.
..
I noticed the EAS™ eGaNAMP2016 amp module is amazingly small (4 x 2 inches) and efficient (96%). The switching frequency is still sub 500KHz but, as you stated, this can be raised substantially with the use of heat sinks. Class D sound matching or surpassing the sound of class A?

Please buy 4 of these modules from EAS and put them in nice chassis with XLR inputs, heat sinks and at least 1.6 MHz switching frequencies. I’ll buy a pair and you keep the other 2 and we’ll report back here on the performance results.

Thanks,
Tim

Getting back to singintheblues original question:

"Which Class D Amplifier? PS Audio, Ghent, Nord, Merrill or other???
Which company is producing the best sounding Class D?
Which models should I be looking to demo?"

singintheblues,

Since you never listed your budget and stated you’d like to demo the best current class D amp, I’m assuming that means price is of no concern to you.
If this is the case, I would suggest you demo the new Merrill Element 118 mono blocks. They utilize the latest very fast switching GaN FETs, have a PWM switching carrier frequency in the MGHz range and I just read a great review on them on Enjoy the Music. Here’s a link:
http://www.enjoythemusic.com/superioraudio/equipment/1018/Merrill_Audio_Element_118_Monoblock_Amplif...

Tim

Hello atmasphere,

     I think I understand; while GaNs do switch much faster than traditional MOSFETs they still require some driver circuit current to operate.  The use of GaN FETs results in significantly lower gate capacitance and stored charge but not to zero. 
     You're stating the most important benefit of using GaN FETs in a class D amp, however, is reducing dead time (possibly to zero at current class D switching frequencies.) since this allows for the further reduction of distortion.  It seems to me that the benefits of GaN technology will improve the performance of all types of ss amps, not just class D.
     Please let me know if I'm misunderstanding anything.
     I'm also curious about how your development of a class D amp is progressing and whether it will utilize GaN  or any other newer technology.  
     I'm very interested and anxious to actually audition and experience the performance improvements gained through well designed amps incorporating the best of existing and recent technology.
Thanks,
  Tim


     I think of ClassDAudio as the bargain center for class D amps.  This is the place to go if you want high quality class D sound for the least amount of money.  
    About 4-5 yrs ago, there was a lot of buzz about how good class D amps were getting and that they were moving beyond just good sub amps and were beginning to be considered very good sounding amps from top to bottom frequencies. They seemed to be the amplifier technology of the future since they not only sounded very good but were powerful, could easily drive low impedance speakers, were smaller, lighter, more electrically efficient and ran cooler than other more traditional ss and tube amp types.
      I was very curious to try one and see what all the fuss was about.  So, I called ClassDAudio and talked to the owner, Tom Roth, who's very nice and knows a lot about class D. 
      He recommended I try one of his completed amps. the SDS-440-CS, to drive my large 4 ohm Magnepan 2.7QRs.  This was my first class D amp and it was an excellent performer.  Mainly out of curiosity, I've moved on to a few other class D amps but the ClassDAudio is still operating flawlessly driving the rear surrounds in my system.
     I expect his new class D amp using the GaN FETs will also be a bargain.
     I find his comment that "were're still finishing case design" to be a little worrisome.  While he makes great sounding class D amps using lesser known modules and traditional toroidal power supplies, the styling of his amp cases are typically, and to be very generous, ugly as sin.  Think anti-Jeff Rowland Design Group style.
     Hopefully, this amp case's styling will match, what I expect to be, the great sound of his new amp.

Tim


     I agree the glass tube containing the GaN module is a bit goofy.

     But I think something like this on a class D amp, a convenient location where some type of plug-in is inserted to change the amp's sound characteristics using a variety of purchased opamps or dsp chips, might be kinda cool.  Like Nord but more convenient/accessable.
     Maybe they could offer 'Classic Tube Sound', 'Flea Watt SET Sound with SS Bass', 'Lamm Tube Amp', "McIntosh', 'Pass Labs SS Amp', etc.
     They could also have a class D preamp with these plug-ins so one could match various preamp qualities imparted to various amp sounds and tailor the sound just to their liking.
     I  think this type of technology could be feasible in the near future.

Tim
      


I found some interesting You Tube videos of the new ADG Vivace GaN mono blocks:

1. A pair of the new ADG Vivace GaN monos driving the mids/treble of a biamped speaker with the bass driven by an older pair of Rowland Model 12 class D monos compared to 2 pairs of Rowland Model 12s driving both.

2. A pair of the new ADG Vivace GaN monos driving the mids/treble of a custom biamped Magnepan speaker without the bass being driven at all compared to 2 pairs of Rowland Model 12s driving both the mids/treble and bass.

Here are the links: https://www.youtube.com/watch?v=KJb3pOY4tGA
https://www.youtube.com/watch?v=KJb3pOY4tGA&t=392s

3. B&O ICE Module 250ASX2 with tube input. (500wpc@8) vs. Jeff Rowland 535 (250wpc@8) vs. AGDProductions Vivace monos.

Here’s the link: https://www.youtube.com/watch?v=b-HFVPvWHTw

It is true that the comparison is limited by the audio quality on a You Tube video, but I found the audio quality sufficient enough to still convey the clear superiority of the GaN amps. Of course, I’d prefer comparing the sound quality in person.
I also thought the ADG Vivace amps, with the gimmicky large tube shell containing the GaN FETs protruding from the top of the amps, actually looks much less goofy in action than I originally thought it would. My current opinion is that it’s a good tip of the hat to the fondness most tube lovers, including myself, have for the warm glow of tubes in a darkened room that is remininscent of good music flavored with a touch of euphonic joy.
These videos struck me as satisfying confirmations of the benefits GaN FET technology can contribute to the sound quality of virtually all solid state amps.

Tim

Correction:  I mistakenly stated the older Rowland Model 12 amp is class D in my last post.  It is actually a class AB amp.

Sorry,
 Tim
kgturner,

     I don't know what the general opinion of those following this thread is but my opinion is that these mono blocks are excellent amps.
     Kharma, mainly a hi-end speaker and cable seller at the time, introduced their first  class D amps  (the MP150 and MP350) in 2007. Kharma owner, Bruce Oosterum, collaborated with class D UcD inventor, Bruno Putzeys,  on these UcD based amps.
     Putzeys had claimed to be able to bend the sound of any class of amp, be it A, AB or D, to his will.  So the design goals for the new Kharma amps was to make them sound like a tube amp in mid and high frequencies and retain class D's traditional excellent bass response. 
     As you stated, according to the reviews of the MP150 from The Absolute Sound, Stereophile and 6 Moons at the time, they were very successful.
     Around 2010, I heard a pair of MP150 mono blocks driving a set of Magnepan 20.1s playing vinyl and it sounded spectacular.  I wanted to buy a pair for my Magnepan 2.7qrs but the price was too steep for me at that time; about $7K/pr. if I remember correctly.
     I'm very satisfied with the much newer and higher powered D-Sonic class D mono blocks I'm now using with my Magnepans but I wouldn't be surprised if a pair of the Kharma MP150 monos, even a 10 yr old used pair, sounded just as good or possibly better.  However, I heard them on the top Magnepan speakers which isn't really apples to apples, either. 
     I'm also not sure whether Kharma has updated the MP150 over the years.  I think Kharma has since offered an MP1000 model amp that is class A/AB.

Tim
Hello atmasphere,

Thanks for the update. Very interesting and surprising, too. I’m not surprised you’re building your class D modules by hand but I thought you’d decide to utilize the faster switching GaN FETs in your amp. I would think not using them would handicap your amp’s performance in relation to the competition. I assumed you’d choose the best parts for each amp function in order to optimize overall performance.
I’m just an enthusiast of good music played through high quality audio equipment but even I can hear the improvement in sound quality of the ADG Vivace mono blocks despite listening to them on a YouTube video on a laptop via headphones. I think the improvement would likely be even more obvious and impressive heard in person.
I may be attributing too much credit to the faster GaN FETS, rather than the typical silicon MOSFETs , for the improvement in sound quality I hear in the new ADG amp. I know there're many other design factors involved in determining an amp’s ultimate sound quality.
But I understand that you’re an amp designer who’s also responsible for running a successful company and there’re very important factors involved in your choices that I’m not aware of. You certainly don’t owe me an explanation, I think I’m just a bit perplexed and disappointed.

Best wishes,
Tim
tweak1:

"Paraphrasing your reply, Class D is ruthless on ancillary kit and cables. They should be upgraded before bashing class D."

Hello tweak1,

Great to hear that you’re benefiting from the detail and clarity of class D technology to significantly upgrade your system’s ancillary power cords and cables. I had similar improvements in my system by installing custom made XLR cables between preamp and class D mono blocks and power cords on my monos (all ordered from James Romeyn Music LLC). I also installed dedicated AC lines for the monos that made obvious improvements.
Similar ancillary kit and cable changes, as well as the quality level of source recordings, were never this clearly noticed through the decent quality class AB amps I previously used.

Enjoy,
Tim

atmasphere:


"^ The reason we aren't using GaNs yet is we are in a prototype stage. We developed a means of eliminating the need for dead time circuitry in class D amps (for which we have a patent pending).

The main reason to use GaNs is to minimize dead time (dead time increases distortion). So you are seeing GaN-based class D amps right now that have no dead time circuits simply because the transistor is so fast that with conventional switching speeds no dead time circuits are needed. 
We're able to switch at the same speeds with conventional devices."

Hello Ralph,

     I would like to retract my complete previous post addressed to you.  I had a hunch you had your reasons for not using the new GaN FETs, but I had no idea those reasons were so completely awesome and with a patent pending, to boot. This is really big news that sounds like a major breakthrough in your class D amp efforts to me.  

Breaking News: Atmasphere Ralph just killed dead time.  Congratulations!  
    Please accept my apologies for ever having doubted your judgement.  The legend of your amp engineering and design prowess just continues to grow. Best wishes on your patent application.  Yahtzee!

Thanks,
 Tim 
tweak1,

It sounds like you have a lot of experience which I think is critical in building a system you really enjoy. Listening to the opinions of experienced individuals on audio forums like this is helpful but I believe most of us learn best from actual personal experience. The process of just trying different things ( amps, sources, speakers, positioning, room treatments, cabling and even tweaks), over time, results in a solid foundation that not only lets you know what sounds good to you but also how to attain those sound qualities in your own system.
My interest in class D amps began by reading numerous positive comments on them here and on other audio forums. Eventually, I just bought one (a ClassD Audio SDS-440-CS stereo unit) more out of curiosity than anything else.
I was amazed at how well this small, light, efficient and inexpensive ($600) amp powered my inefficient Magnepan 2.7QR speakers. It was better in every respect than the class AB Aragon 4004 MKII amp I used previously and it was about a third of the size, weight and cost.
Actually trying it out in my own combo music and ht system convinced me how exceptionally well this class D amp performed and I was now curious about the differences between class D amps. Within a year, I bought a few more class D amps: a stereo Emerald Physics EP100.2SE and a pair of mono block D-Sonic M3-600-M amps. These both sounded very good and similar but with better dynamics and improved midrange/treble qualities I’d describe as warmer and smoother.
My entire 5.1 ht surround and 2-ch music system is now powered by class D amps and I’ve sold all 3 of my previous stereo class AB amps. My system’s never sounded better and there’re no downsides.
I think the class D experience I’ve gained has also allowed me to confidently realize that class D critics are typically either misinformed, have an ulterior motive or simply have no personal experience using good examples of them.

Later,
Tim
Hello Tweak1,

    Thanks for the heads up on the AA amps. I'm currently using the EP in bridged mode on my Magnepan CC3 center ch.  
    I discovered both the AA and EP amps use the older UcD class D power modules that are still very good.  Since you own both amps, I don't doubt your view that the AA implementation is superior but rather question whether the performance improvements would be sufficient, in mono on a center ch speaker,  to justify the $ outlay.
    I'm thinking it'd be more beneficial to compare my current monos driving my L+R mains to monos utilizing the new GaN FETs or the upcoming Atmasphere class D amps that may perform even better.
     I have a combo ht and 2-ch music system but my priority continues to be optimizing the music reproduction aspects.

Thanks,
 Tim
tweak1:

"Well, just because they both use UcD does not mean they sound the same. I found the EP monos thin in the mids, which exaggerated the highs. They were used with my KCIIs as is the AA amp."

     Agreed.  That's what I meant when I stated "I don't doubt your view that the AA implementation is superior" on my last post.
      'Implementation' referring to how AA and EP implemented or incorporated the similar UcD class D power modules in their amp designs, with the understanding they're not identical and that you thought the AA implementation was superior based on its sound quality.

Thanks,
  Tim

     No problem.  
     I think the biggest news of this thread is Atmasphere's upcoming introduction of a class D amp that will likely eliminate dead time with new circuitry that has a patent application pending and doesn't even require the use of the new GaN FETs.

    Things are progressing so rapidly in class D technology gains that the answer to this thread's question, which class D?, may be to just save your money and wait a while..... the answer will likely change, in absolute terms and probably especially if the price/performance ratio is considered.

Tim
tweak1,

Forgot to mention:
     I think it’s very interesting that your getting PS Audio 700Ms and the gaincell dac/pre at a great price.
I’m always interested in learning about others' experiences and views on class D amps and other equipment. 
     I find the 700Ms particularly interesting class D amps because they use what PS calls the 'gaincell'.  This is a fancy name for their proprietary, fully differential, zero feedback,discrete class A MOSFET input stage.  These amps don't utilize the new faster switching GaN FETs but, from the reviews I've read, they're high quality amps that will likely further improve the sq of your system. I'm not as familiar with their gaincell dac/pre but plan to read up on it.
     I know it's always exciting to install new equipment in one's system.  I wish you the best and look forward to your reports on the results.


Enjoy,
 Tim
 
      

     I read the Stereophile review on the PS 700Ms and it was very positive.  The review was from Jan./2018 and the reviewer had just previously reviewed the AA DPA-1Ms.  
     He thought the PS 700Ms were superior and even compared them to being somewhat similar in sound quality to the Theta Prometheus mono block class Ds that go for $12k/pr, saying they were a bargain at about$3k/pr and you said you bought yours for even less.
     He also thought they performed best when separated on isolation stands and not stacked on top of each other.   Here's the link:
https://www.stereophile.com/content/ps-audio-stellar-m700-monoblock-power-amplifier
     If they sound as good as they look, these amps should sound very good.

Enjoy,
 Tim
     
    
jetter,

     The Stereophile reviewer heard significant sound quality improvements with separating the PS 700M monos and having them both on amp isolation stands rather than stacked.  
     I'd suggest just trying the amps both ways in your system and determine if you perceive the same significant improvements he mentions.
     If you do perceive large improvements, buy a couple good amp stands and locate the amps separated by placing one on each side of your rack on the floor or place one beside/behind each of your main speakers.  This would require longer inter-connects and shorter speaker wires but this shouldn't cause any issues with that.
     If you don't perceive large improvements, buy some sorbane pads or the blocks cited in the Stereophile review and stack 'em.
     I use thick maple amp stands (from Mapleshade) with conical brass spiked footers on my class D monos but I have room on the 6' wide top shelf of my rack with one at each end for a symmetrical look.  This works well but I never even thought of stacking them ( they're only about 7"w x5"h x 12"d) so I never compared stacked to separated.  
Tim
Jeff,

     Exactly, your description is what I hear listening to very good class D amps.  "There is generally a more relaxed presentation of the music because of these attributes" is an accurate summary of what to expect. 
    Besides the relaxed and seemingly effortless presentation, I would only add my perception that, due to their very high signal to noise levels and the resultant very low background noise levels, music seems to emerge from a dead-silent and inky black background that enhances the whole experience.
Tim  

Uh-oh, it sounds like clearthink isn't thinking too clearly.  Maybe his user name is satirical?

Tim
Hello Guido,

     I had no idea you have such a musical background, very nice. 
    My typical initial reaction, when I read negative comments about the sound quality of class D like those in clearthink's post , is to wonder exactly which class D amps they listened to that was perceived as sounding so bad.  
    My next reaction, that seems to be similar to yours, is that they certainly did not listen to music amplified via my class D amps in my system since I always completely fail to recognize any of the supposed class D negative qualities they mention.
     Unfortunately, I recall only 1 class D amp critic listing the brand and model of class D amp on his post that he had listened to and based his opinions on.  
      I welcome honest criticism of specific class D amps within the context of specific systems.  However, some generalizations of class D performance  (such as "I personally find that class D amplification sounds just dreadful to those familiar with the sound of real music, instruments, and acoustic spaces", "class D treble is harsh and fatiguing", "the soul of the music is missing" , "there's something missing", etc.) without mentioning any class D amp or system details are so broad and unspecific that they become meaningless.   

Tim    
selecthifi,

     Very good news that a completed class D amp using Hypex's top NC1200 modules and powered by their top Hypex SMPS1200A700 PSUs will be available soon from Nord for 3,995 pounds ($5,214 usd).  
     With class D amps using the new faster GaN FETs availability increasing and entry prices decreasing, I doubt Hypex's decision to now allow Nord the use of their top NC1200 modules is a coincidence.
     This new amp from Nord raises a few interesting questions:

Why has Nord limited the class A output current of their custom buffer feeding the NC1200 module in this new amp to 250mA? 

Is Hypex clearing NC1200 module inventory prior to introduction of a new top module, or even series of modules, utilizing the faster GaN FETs?

What are Hypex designer, Bruno Putzeys, opinions on the new faster GaN FETs and does he plan to incorporate them into his future class D module designs?

Tim

     
     It looks like Bruno Putzeys new company, Purifi, has more interests than just class D amps:

https://www.purifi-audio.com/index.php

Tim

Hi Guido.
Thanks for the info, my friend. Very interesting about Bruno leaving Hypex to found Purifi.
The progress of class D technology continues to be very interesting and promising.

Tim

ricevs,

     Thanks for clarifying.  I knew it was a class A input buffer stage, which is good, but wondered if its 250mA class A operating limit would negatively affect sound quality performance.  I now understand it will not thanks to your very good explanation.

Thanks,
  Tim
tweak1:
"I hear zero nasties unless recorded on the cd, and boy I can really hear how poorly mastered some cds are."

Hello tweak1,

    I'm glad you like the initial sound of your new PSA 700M amps. My class D amps have only improved in sq over time.
     Some of the main and most obvious characteristics of good class D amps are their neutrality, low distortion and low background noise level. These qualities combined together results in a highly transparent and detailed presentation that is very revealing. As you're aware, good recordings sound amazingly good but bad recordings sound obviously bad, too. 
     However, I don't think anyone would describe the accuracy of good class D amps as a downside. I believe a person can be guilty of being too truthful and honest but not an audio amp.
     Some may prefer a less revealing amp that doesn't so clearly demonstrate the poor recording quality of some of their musical content. It is frustrating to discover some of your music was not well mastered and recorded.  But I still prefer the accurate and honest attributes because the good recordings sound so incredibly good.
     Unfortunately, good recordings of good music are not as abundant as I'd like but that's a whole related subject that's justifiably been the topic of  other separate threads in the past.  

Tim
tweak1,

     Understood.  I no longer listen to Coldplay discs on my home system due to poor recording quality but I still enjoy these discs on my OEM car system.
     I've discovered that music files recorded direct to digital are especially good source material that are consistently well recorded and mastered.  I have several hi-res 24bit/96KHz FLAC files downloaded from a Dutch site called Sound Liaison:
https://www.soundliaison.com/
     
     These are all direct to digital master recordings of live music played at their large studio. Downloads are available in various digital formats from FLAC to DSD.  
     The audio quality is excellent top to bottom with uncompressed dynamics that make them easily sound better than my ripped cds. 

Tim