Class D is just Dandy!

Northernfox,

      Congrats on your new Bel Canto Ref600M class D mono-blocks!

      From the reviews I've been reading, good amp designs based on the newer Hypex NCore 500 module are very close to the good amp designs based on the NCore 1200 module for about half the price.  I haven't heard them yet but will make a point of auditioning them asap.  
      You're obviously already very pleased likely without complete break-in, which means they're only going to sound similar or even better going forward.

  Enjoy,
    Tim

     Class D's current state is very good and its future is looking even better.  I recently read an article about new faster switching MOSFET transistors.  

      This transistor technology is called Gallium Nitride (GaN) and is poised to uproot the high-end audio world. In fact, GaN-based Class D is much more power-efficient than traditional, MOSFET-based Class D and offers orders of magnitude better performance. Performance that to many listeners, even surpasses the quality of Class A.   At any given product price point, these new Class D solutions can meet, or surpass the quality of today's linear amplifier solutions. As an example, the eGaN FET-based Class D amplifiers can easily achieve a mid-band THD performance of 0.005%, where a comparable linear amplifier Class would achieve around 0.05%. Here's a link:

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

     Just to make sure everyone was aware of this important new class D development, I also posted this link on the "class D=Trash?" thread.

Later,
 Tim

" Yes as I posted here, these eGaN fets are what Technics are using in their new $30k class-d and with it are able to double the frequency of the switching noise."


     Yes georgehifi, you were definitely the 1st to post here and link info on the eGaN FETS that are used in the new Technics amp.  I recently happened upon an article about the eGaN FETS while on Audiophilereview.com and didn't recall your earlier posts about them. 

My mistake and apologies.  I forgot you've been saving up for this $30,000 class D amp.
          Tim    

     I also have high expectations for the use of faster switching GaN  output transistors in class D amps since they have the potential to eliminate dead-time, which even further reduces distortion, which in turn,  typically results in improved sound quality. 
     I've been using good quality class D amps in my combo music and HT system for almost 6 years now.  In my opinion, they're the best option for attaining hi-end amp performance quality at an affordable price.  
     In my experiences with good quality class D amps, I've discovered their most unique quality is that they have no sound qualities of their own.  They just faithfully amplify the inputted signal without adding or subtracting anything.  They're like the audio amp ideal of a "straight wire with gain".
     Due to this extreme neutrality of class D amps, I've come to the conclusion that the most important factor determining the overall sound quality level of a system utilizing a good quality class D amp is the sound qualities of the preamp  chosen to pair with it. This neutrality also means the overall system sound quality contributions made by source components, and even interconnect and power cables,  will be readily apparent and need to be chosen carefully, too.
     I've not yet listened to a class D amp utilizing the much faster switching GaN transistors but am looking forward to doing so, hopefully, at an affordable price.  Based on my experiences with good quality class D amps, however, I suspect the use of GaN transistors will result in these amps being among the most neutral ever produced.  Choose your preamp, source components, interconnect and power cables appropriately.

Tim

Hi Erik,

     I just started reading your last post and clicked on your 1st link.  I took me to this Audiogon forum page instead of the diyclassd page I think you intended.

Thanks,
  Tim

miner42,

     Nice story except for the part about your brother in law dying!
     It just illustrates another less discussed benefit of good class D amps; reliability.  
     Most understand that heat is generally the enemy of electronics and excess heat can cause premature circuit or part failure.  Class D amps generally run so cool they don't even use heat sinks unless an analog power supply is substituted for the cool running  switch-mode power supplies (smps) typically utilized with, and even now built into, the
 class D power modules. 
     This lack of heat buildup, I believe, can only benefit class D amps and increase their reliability and extend their lifespans as a result.
     I also believe the opposite is true of class A and A/B amps specifically because they run much hotter..
     Great sounding, very quiet, very neutral, relatively inexpensive,very detailed and powerful amps with low distortion, wide dynamics  and very detailed from top to bottom.  What else would you want to consider an amp type ideal?  Oh yeah, have it consume electricity like a virgin consumes birth control pills, keep its cool like Clint Eastwood and, while you're at it, make it as reliable as Old Faithfull.  

     'Mr, Old Faithfull', Georgehifi, predictably would add that increasing the switching frequency to 3-5 mHz would make class D perfect  My opinion is that this may be making perfect the enemy of the extremely good.

      What the Heck, though, if it'll nudge class D firmly into the 'Ideal Amp Technology' consensus, the brains behind class D are likely pondering this as we speak.

      If Bostrom at Anaview/Abletec, Putzeys at Hypex or Hansen at Pascal determine that a higher switching frequency would actually benefit the performance of their class D modules, I would not wager against them incorporating this improvement into their products.

      Unfortunately, I'm not technically knowledgeable enough to determine whether a large increase in the switching frequency would actually improve class D amp performance.  As I've mentioned before, I detect no sonic detriments to the current switching frequency operating in the mid 500kHz range.  Obviously, though, I've also never been able to compare a class D amp with a switching frequency in the 500kHz range to an amp with a switching frequency in the 3-5 mHz range.

     I'm also a bit perplexed on whether and how this switching frequency issue affects the Bostrom/Anaview-Abletech and Hansen/Pascal class D modules' performance since they both now operate utilizing Phase Modulation rather than the Pulse Width Modulation still being utilized in the Putzeys/Hypex, along with being utilized in most previous, class D modules.

     Sorry to get so Geeky about this, but I've read and paid attention long enough about class D technology to be dangerous without completely grasping the subject.  I think it would help me if someone had the time, expertise and ability to explain this further in layman terms.

Thanks,
  Tim   

I wanted to describe an additional benefit of good class D amps that I quickly discovered after switching from my former class A/B Aragon 4004 MKII amp to my first class D amp, a ClassD Audio SDS-440-CS stereo unit and is a quality of all 3 class D amps I’ve owned thus far: the latest 2 are an Emerald Physics EP-100.2 and a pair of D-Sonic M3-600-M mono-blocks.
It’s a benefit I never read about in my prior research on class D, still don’t read much about and that I believe is common to all good class D amps and not unique just to my 3 amps but I’m not currently certain.

As many of you already are aware, humans generally perceive bass and treble frequencies to be attenuated relative to mid-range frequencies when listening at lower volume levels. This means as volume is reduced, the less we perceive the bass and treble frequency extremes and the more the mid-range frequencies predominate; which flattens out the perceived sound since the mid-range frequencies are accurately perceived but the bass and treble frequencies are perceived as under emphasized. Some of you are old enough to remember ’loudness buttons’ on receivers from the 1970-1980s. These controls were used to boost the bass and treble frequencies when listening at lower volumes to compensate for this known deficiency in human hearing.

Okay, enough preamble. I’ll describe the class D benefit now even though I haven’t yet thought of a better short description of it than ’a consistent and continual loudness contour’. I began carefully listening to my first class D amp at a lower volume and immediately noticed the sound was much different than I was accustomed to with my class A/B amp at lower volume. There was no flattening of the frequency range, I perceived the entire frequency range of the music with seemingly no under emphasis of the bass and treble. This struck me as amazing since it was the best I had ever heard my system sound when listening at a low volume.

After a few days of listening I decided it was safe to experiment with higher volume listening levels closer to the levels I formerly listened to music at with my class A/B Aragon amp (probably in the 70 db and up range). As I began slowly increasing the volume, I was pleasantly surprised to notice the frequency range balance or perspective of the music remained constant while everything within this perspective just gradually increased in volume. The music sounded well balanced and enjoyable from low volume to high and all points in between.

This well balanced frequency perspective was also consistently maintained even at volumes well above my normal listening level.
Some of you with higher quality systems are probably thinking ’what’s the big deal’ about turning the volume up and the music just gets louder without the fidelity or overall frequency perspective within the sound stage changing but this was revelatory amp quality behavior in my experience. My former Aragon didn’t sound near as good at low volume levels and required volume levels in the 70 db plus range to sound its best in my opinion. Music at low volumes seemed to flatten out with attenuation in the frequency extremes.

I’m a bit embarrassed. As I’ve written this post, I’m thinking the quality of my former Aragon class A/B amp may have been lower than I thought or it was gradually aging and sounding worse just prior to the power supply caps leaking and it going belly up. Perhaps I was just hearing the difference between an older amp on its last legs and a brand new class D amp of good quality.

Well, at least I consider the good sound quality at any listening volume a class D benefit and hopefully others who may enjoy listening at lower or very high volumes will find this attribute useful as well.

Thanks,
Tim

"randy-11
higher switching frequency moves it further from the range of human hearing and enables "kinder, gentler" filtering

georgehifi
+1 many times over Randy, seems like your one of the few that get it here!"

randy and george,

     I believe I understand george's often stated theory that the current typical class D switching frequency is too low at about 500kHz and results in sonic anomalies within the audible human hearing range of 20 Hz to 20 Khz. This theory further claims that raising the switching frequency to the 3-5 kHz range will cause these sonic anomalies from affecting any frequencies within the audible range of human hearing capacity. 
 
     My issues surrounding this class D switching frequency theory, that apparently both of you now support, are twofold:

1.  Whether to believe 2 people on an audio forum named randy and george, of uncertain class D technical knowledge and credentials,claiming this switching frequency theory is valid but offering no supporting evidence

 OR
 whether to believe the actual inventor of class D amplifier technology named Bruno Putzeys who seems to assign no validity to this theory and has stated that "500 kHz is a completely reasonable class D switching frequency".
 Written down like this,  it seems like an especially silly and obvious choice to me concerning whose advice I should rely upon in evaluating this theory.  Are you two really suggesting I simply ignore the inventor of Ice and NCore class D power modules and just trust your viewpoint instead?
   If it was empirically proven that these sonic anomalies exist and are audible to a significant number of humans, I admit I would be curious to determine if it improved the sound of my system once the price was much more affordable  As it currently stands, however, I'm not convinced I should care since I've never even heard a hint of any sonic anomalies from any of the class D amps I've used in my system or any I've ever listened to in any system.  
   
     As Aristotle so famously asked Plato so astutely long ago:
"If  your class D amp had a switching frequency proven too low and it caused audible sonic anomalies, but you could not hear these anomalies,  would they even exist to you?"

    That hipster Plato then replied to his teacher in the following lesser known and less famous manner:
 "Mr. Astute, if I cannot hear them pollute then it does not compute and I know the point is thus moot so I properly cease to give a hoot."  True story. 

       I'm with Erik and Plato on this one; I've been living with dreamy sounding amps for a while now, too. I don't need my switching frequency increased to have what I consider the best, either.

Later,
 Tim

"  just tested it. It actually is a PDF download, so check your download files. :) "

Hi Erik,

You're right, I opened the pdf on the Ncore 400 module.

Thanks,
  Tim

georgehifi,

  Your most recent post, posted last night at 10 p.m., consists entirely of a quote from the author of an article on www.audiophilereview.com, Skip Taylor, that is dated 9/21/2016 and is titled Why We'll Soon Be Living In A Class D World.  You and I have both previously linked to this article on this thread; you initially then me subsequently, mistakenly and redundantly.

     I'm not sure why you felt the need to also post that specific portion of the article again, this time in quote form rather than a link, since your post lacks any pre or post quote comments.

    atmasphere and I previously expressed concern with the author's inaccurate terminology and his knowledge of how class D actually functions.  

    Now, I want to freely admit upfront again that I do not claim to be technically knowledgeable of electrical engineering generally  or how class D functions specifically.
   Even a class D fan but technical layman such as myself, however,  is able to find fault with some of Skip Taylor's article and question whether he has a firm grasp on how class D actually functions.  I'll just critique one sentence you quoted from his article to explain my concerns from my layman's perspective:

"The greater switching speed of Efficient Power Conversion's (EPC's) eGaN® FETs allow amplifier designers to increase PWM switching frequencies, reduce dead-time, and drastically reduce feedback; in turn, producing a sound quality previously limited to large, complex, heavy Class A amplifier systems."

My concerns with this quote are:

1.  I think most are aware that MOSFETS are used as electronic switches in class D amps, required to turn on/off very quickly as the PWM (Pulse-Width-Modulation) circuit's introduced ultrasonic switching frequencies dictate, rather than as linear gain devices as in other traditional linear amps. Given this,  I think everyone understands that the new eGaN® FETs, having the ability to turn on/off much faster than MOSFETS, will allow amplifier designers to increase PWM speed thus reducing dead-time, something called 'shoot through' and distortion.

  But how do these new eGaN® FETs allow amplifier designers to increase PWM switching frequencies? He mentions this as if it's a direct result but without any further explanation.
  He fails to mention whether current PWM switching frequencies are too low and whether they cause any proven audible sonic anomalies in current class D amps' outputs.  He also gives no explanations or proven scientific facts as to why higher PWM switching frequencies are desirable or would be beneficial.  

2.  Skip Taylor states that the new eGaN® FETs will allow amp designers to drastically reduce feedback in class D amplification,  something that may be beneficial in traditional linear amp design but I'm not certain he realizes that reducing feedback in class D amps has no relevance since high levels of feedback is a major factor/tool utilized in good class D amp design.  As the inventor of Philips Ice and Hypex NCore class D power modules, Bruno Putzeys, often states: "there is no such thing as too much feedback in  class D amp design".  

     While I agree with Skip Taylor's article title that we'll all soon be living in a class D world since many of us already are, I also got the impression from his article that he doesn't have a complete grasp of class D amplification.
     Please take the above only as the reduced value opinions of a declared layman who isn't as concerned with how class D functions as with how good it already performs.
     I've been listening to some computer audio music files as I write this post;  Two very good albums from Carmen Gomes  that were recorded direct to 96kHz/24bit  high-resolution digital: the highly recommended Thousand Shades of Blue and Torn(SE).  These downloaded  files are one-to-one exact copies of the masters recorded live, unedited, unmixed and without the use of compression in front of a small audience at the legendary Dutch Studio Eleven with just left and right main mics and a few additional mics for the minimal instrumentation.  Most songs  are intimate- jazz-club like tracks with the beautifully soulful, smooth and sexy lead vocals of Carmen Gomes backed up by a small but very skilled group of clearly jazz/blues influenced musicians on guitar, drums/percussion and double bass.  

   I mention this because I believe  the combination of very low distortion, low noise, extremely  detailed, completely uncompressed and accurate  source material that direct to hi-res digital recording provides paired with the very low distortion, very low noise floor, very neutral tonal quality, powerful dynamic ability, highly detailed and accuracy that good class D amplification allows produces the most life-like and natural reproduction of live music that I've ever been able to attain in my system by a wide margin.

    Now georgehifi and randy-11, are you both claiming I'm currently attaining this extreme level of system fidelity despite the presence of sonic anomalies in the audible frequency range caused by my class D switching amps' switching frequencies being too low?
     Have you guys even considered the possibility that your unproven switching frequency theory is unproven for a reason?
     Do I, and all of the thousands (millions?) of other class D users and fans just have tin ears?
     Why do only you two contributing thus far on this thread apparently buy into this unproven class D switching theory?
     Do you both have canine-like hearing and inexplicably obey dog whistle commands?
     I actually hope you two pooches are correct and class D switching frequencies in the 3-5 mHz range really do eliminate the sonic anomalies that it seems most  users cannot currently hear.  
     I'm just wondering how we'll be able to perceive the absence of something as a sonic improvement when we didn't perceive the presence of that something in the first place.
    But heck, let's look on the bright side, at least you two good doggies will appreciate and possibly even salivate at the suspect improvement if your theory is correct. 
     Sorry guys, but I think you two 'woofers' may be barking up the wrong tree. 
Later,
 Tim

"Tim,
Ofcouse I have read all this info before,I appreciate you taking the time to post all of this pertinent info so others can read it too."

Hi kdude66,

     Thank you, but I actually really enjoy reading the Audiogon and other audio and video forum threads on-line and contributing my version of the truth especially when I believe I have useful input based on personal knowledge or experience related to the subject being discussed.  
     Unfortunately, I had emergency open-heart surgery about 8 yrs ago and suffered a stroke immediately following the surgery when I was relatively young at 51. I recovered my cognitive and speech abilities rather quickly but I’m still trying to coax my paralyzed left limbs back into action. I decided to retire early after consulting with my cardiologist and neurologist and am currently on SS Disability Insurance with a reasonable but fixed income until I reach my actual retirement age in about 8 yrs.
I wasn’t prepared for how much I actually missed my job as an operations manager at a very large (1 million sq. ft), high volume, fast paced and highly automated distribution facility and the people I worked with, Oddly, my dreams often revolve around work and my former colleagues. I’ve even awakened many times in the morning thinking I need to still solve fairly complex problems or employee situations I was dealing with a few minutes earlier in my dreams.
     So, while I feel grateful I’m still on ’the right side of the grass’, I’m also grateful for this forum that enables me to keep learning from other members about this hobby I’ve enjoyed for decades and post my thoughts when I think I can contribute constructively on certain subjects.
     As my typically overly long posts indicate, I now have plenty of spare time to read and respond when I may be useful to forum threads, too.

     Like this thread for example. I initially learned of class D amps from positive comments on various audio threads. I purposely began researching all I could on the subject here and on other sites and I credit my own quasi-scientific readings on the over 60 yr history of class D amp development along with the forum posts of class D guru Guido Corona and a few other members with exceptional knowledge and experience.
After my older class A/B amp went belly up due to leaking caps a few yrs ago, it was the perfect time to take the plunge and start gaining some personal experience with class D and I bought my first amp, a Class D Audio SDS-440-CS stereo unit that was superior in virtually every aspect that audiophiles care about in an amp. I was so impressed that I replaced the other 2 class A/B amps I used in my combo 2-ch music and 5.1 HT surround system with relatively inexpensive class D amps; a Emerald Physics EP-100.2 stereo unit and most recently a pair of D-Sonic M3-600-M mono-blocks.
     When I read posts from members like georgehifi and randy-11 about a theoretical issue with class D amps switching frequencies needing to be dramatically raised to avoid affecting frequencies in the human audible hearing range without presenting any semblance of even anecdotal evidence that it’s true, makes me seriously suspicious of their true motives for spreading and trying to validate something that I highly doubt 99%plus of humans could even begin to detect, although I believe at least georgehifi has heard a good class D amp and acknowledged how good they currently are but is going to wait for his view of perfection. I’m not even sure if either one of these guys has personally heard any sonic anomalies from a class D amp.
As far as I’m concerned, they’re in my doghouse until they can cite a SPECK (as in Peewee Herman’s dog) OF EVIDENCE.

Tim

     georgehifi happens.

      If you know what I mean.

Tim

+1 atmosphere
     Another prime example of the universal principle that
 georgehifi happens. 

      Due to the vast amounts of prior fecal matter georgehifi has dropped on this Audiogon Forum over the years, an elite group of the world's best scientists currently believe after completing their thorough analysis of this over abundance of raw data, that this principle can be relied upon to such an exceptionally high degree without a single exception that this Principle merits upgrading to a Law, pending peer review.

Tim

randy-11:
"Can anybody list very affordable great sounding Class D amps - say below $2,000 for a stereo pair, and better or comparable SQ to a Sunfire amp?"

I'm not sure if you're looking for a stereo amp or a pair of mono-blocks.

But for stereo amps, I'd suggest:
ClassDAudio  SDS-470C for $700.  I own the model just under this, the SDS-440-CS for $630, and it's a very good performer so I would think the 470-C sounds similarly good with a bit more power than the 440-CS.  Not exactly audio jewelry but bargains sound wise.
D-Sonic M3A-1200S, 2 x 600w  for $1,875. Stereo version of the M3-600 mono-blocks that are very good.
D-Sonic M3A-800S,  2 x 400w  for $1,475. 
Red Dragon S500 2 x 250w currently on sale for $1,899 (reg price $1,9999 black in stock but silver temporarily sold out). Very well reviewed and uses dual Pascal class D power modules usually used in very hi-end amps.

For mono-blocks:

D-Sonic M3-600-M 1 x600w for $2,150/pair.  I've owned these for about 2yrs and use them to drive my Magnepans with 1,200w @ 4 ohms. By far the best amps I've ever used on them.
D-Sonic M3-1500-M 1 x1,500w for $2,750/pair.  I haven't heard these in my system but, based on the rave 6Moons review I read on these, they may give you the best performance short of spending $10k+ on the excellent Merrill Audio Veritas monos. Use the highly regarded Pascal power modules.
Red Dragon M500 1 x250w currently on sale for $750 each (reg price $800 each black in stock but silver temporarily sold out.)  Very well reviewed and uses  Pascal class D power module usually used in very hi-end amps.

     There are others I haven't heard such as the Nord monos from the U.K. and the James Romeyn Hypex NC-400 mono kit amp builds in Utah

Hope this helped,
    Tim
  

     Very nice to see almarg and atmasphere team-up, step up and use their knowledge/experience to solve islandmandan's noise problem. Nice job guys!

     What I've consistently noticed from listening to good class D amps in my system, from my initial Class D Audio SDS-440-CS stereo amp to my Emerald Physics 100.2 to my most recently purchased D-Sonic M-600 mono-block amps, is their exceptional quietness;  music seems to emerge with more impact due to the dead quiet background.
     I believe this silent quality is also a primary contributor to the other obvious characteristic of good class D amps: a very detailed presentation..

      I'm almost certain these class D attributes will now be very evident to  islandman  now that his amps are operating in their typically silent manner.

Enjoy,
 Tim

Hi autre,

     Congrats on choosing the Red Dragon S500 stereo amp.  A very fine example of a class D amp done right.  It utilizes the newer Pascal S-Pro-2 power module that is also utilized in the Jeff Rowland 525 bridgeable stereo amp and the Rowland Continuum 2 integrated and the Gato Audio integrated.  

     These modules have an enhanced and patented class D technology named UMAC, which  integrates the Switching Mode Power Supply (SMPS) with the  Switching Output Stage on one board and not on separate boards like the high-end Hypex NCore amp implementations in which the Hypex NCore 1200 SMPS  and NCore 1200 Output Stage are on separate boards.   This integration enables the Pascal S-Pro-2 to be the most compact 1,000 watt class D professional amp module on the market.

     More importantly, however, is how does this Red Dragon S500 implementation of the Pascal S-Pro-2 power module combined with Red Dragon's custom input buffer stage actually sound?  From the many reviews I've read  on this amp at 6Moons, Dagogo and Audioholics, along with your very positive reports, it's abundantly clear this is a high performance amp.  

     Unfortunately, I've not yet been able to audition this amp in my system although I was very close to buying a pair of Red Dragon M500 MKII  mono-blocks based on their excellent reviews and the very cool Red Dragon logo that lights up on the front of each amp when active (in red of course).  The black units were out of stock at the time and I decided to buy a pair of D-Sonic M600 mono-blocks instead.

      I've been very pleased with the D-Sonics but would still love to try the M500s or S500 in my system just to determine if I made the right choice.
 
     My current opinion is that these are all very good class D amps that I'd be pleased with in my system.

     I'm continuing to enjoy learning about and understanding each individual amp/tree in the exciting and constantly improving class D forest.

      I've also continued to fail to detect even a whiff of a sniff of an inkling of any sonic anomalies in any of my 4 class d amps caused by their mid 500 Khz switching frequencies.

     Is the 'Wonder From Down Under' still propagating his unsubstantiated and debunked theory that class D switching frequencies need to be over 3 Ghz to avoid sonic anomalies in the audible range that no known human has ever claimed to have actually heard?

Enjoy autre,

  Tim

+1naimfan

     Children are not born with biases or prejudices toward any human or amp type, these are both learned behaviors.

Tim

Hi migueca,

     I agree with Erik that the main benefits of mono-blocks, regardless of the amplifier type, are increased headroom and channel separation but with the former being more obvious than the latter.

     Increased headroom in an amp is mainly evident in its ability to more accurately reproduce the large dynamic range of live music.  My experience is that a system's ability to quickly and powerfully reproduce musical passages that progress from soft or moderate volumes to suddenly higher volumes significantly adds to the illusion that you're listening to live music in your listening room; amplifiers without large amounts of headroom and the ability to deliver it quickly typically will not be able to convincingly create this illusion.
     However, there are class D stereo units available that contain 2 power modules, with a devoted power supply for each, combined in a single chassis.  Some of these dual-mono stereo amps even utilize separate power chords for each channel/module.  I've never compared the performance of a dual-mono  stereo amp to a pair of mono-block amps but I believe most people, including myself,  would be hard pressed to  distinguish between the two.

     Technically, with mono-blocks having each channel contained in its own chassis and physically isolated from each other, it would be expected that their scientifically measured channel separation stats are superior to dual-mono stereo designs.  Whether you'd actually hear this superiority is questionable.

     I've used 2 different stereo class D  amps in my system (a classD Audio SDS-440CS and an Emerald Physics EP-100.2 ) and currently use a pair of D-Sonic M-600-M mono-blocks.  I would characterize them all as having very good channel separation with a solid and stable 3D sound-stage illusion.  I haven't noticed an obvious improvement in channel separation with the mono-blocks but have definitely noticed an increase in headroom and a greater dynamic range with the mono-blocks in my system.

     I know from your posts that you're thinking of trying out a good class D amp in your system and you're considering trying a Ghent or a ClassD Audio model.  I highly recommend my first class D amp, the classD Audio SDS-440-CS.  It's a true high quality bargain at only $630.  It's powerful (220 watts @   8 ohms/ 440 watts @ 4 ohms), has extremely low distortion levels, very good bass response, is very detailed and neutral in sound character with music emerging from a dead silent background.  The mid-range and treble response is very smooth and never bright or harsh like a tube amp without the treble sounding rolled off at all.  Here's a very accurate review from a professional reviewer: 
  
www.highfidelityreview.com/class-d-audio-sds-440c-amplifier.html

     They also give you a 30 day in-home trial period with a 'no questions asked free return policy' if you don't like it for any reason.  Very low financial risk involved but I seriously doubt  you'll want to return it.

Enjoy,
 Tim    

migueca,

     I just read a review on the Temple mono-blocks that was very positive:
   www.enjoythemusic.com/magazine/equipment/0514/temple_audio_monoblock_amplifiers.htmat

     I've never heard any of the Temple Audio amps so I'm unable to provide you with any useful feedback.  I noticed the monos are rather low powered at 40 watts/ch (the review doesn't mention whether that's into 8 or 4 ohms).  I believe you know how important it is to match an amplifier's power rating and sound characteristics to your speakers and therefore assume your speakers are very efficient. Please let us know your room dimensions and what speakers you'll be using so we  can offer further guidance.  

Thanks,
  Tim

Hi migueca,

     Okay, 70W on the Zu Omen Defs is plenty of power; almost overkill.  I don't think it's too much since it's such clean, low distortion power  You're virtually guaranteed the amp will never clip and you'll have plenty of reserve power for transients.   I think you're really going to like class D with your Zus and I'm certain there'll be much less heat in your room.
     Sorry for the belated response, I just saw your post.  Have you got the amp yet? I'd like to hear your thoughts on the combo.

Enjoy,
Tim

Hello naimfan


     There are a lot of good amps of all types.  Whatever floats your boat or tickles your fancy.
     We all need to pick our own huckleberry.
Tim

" It is the notion that Class D switching speeds are the cause, and that someday they'll be fixed that irritates me. It's a type of prejudice not born in evidence. It's the equivalent of "all feedback is bad" sales pitch for some amplifier designs."

Hi Erik,
     'A type of prejudice not born in evidence' is a very accurate and succinct way of describing how some class D detractors have a knee-jerk response, whenever class D is mentioned,  of proclaiming a completely unproven theory that current class D switching frequencies are too low and negatively affect frequencies in the audible range.  
     Nevermind that the current leading expert on class D, UcD and Hypex NCore inventor Bruno Putzeys, has stated the current switching frequencies are not too low.  Nevermind that there is absolutely no scientific evidence supporting the claim that current switching frequencies are too low and cause audible sonic anomalies.  Regardless, there seems to be a small group of class D detractors that still claim that current switching frequencies are too low and negatively affect sonics that they're able to detect.
      I've spent more time contemplating this subject than it likely deserves as well as why there are so many class D amp listeners and owners, just like you and I, who perceive no sonic anomalies at all while an apparently smaller group claims to hear some and dismiss class D technology as a result.
    My current thinking, based on multiple threads discussing the amps and technology over the past 5 years,  is that class D detractors and naysayers are best not considered as a single group but as a collection of smaller groups such as these:

1. Those that have never actually listened to a good D amp in their system but simply parrot other critical comments they've read previously.  This group can typically be identified by their comments being more biased toward whatever amp type they own and use than biased against class D. 
2. Those that acknowledge the strong points of class D but consistently mention the same perceived flaw of switching frequencies being too low  This group can usually be identified by a lack of scientific support and a lack of even an anecdotal description of the claimed flaw's sonic affects.
3.  Those that actually do try out class D amps in their system but claim that 'something is missing from the sound' and decide to just continue using their existing amps.  This group can usually be identified by statements containing sentiments about how they really wanted to like class D but liked the sound of their existing amps better. 
      Their existing amps are often high quality and expensive tube and class A amps that are very large, electrically very inefficient, emit copious amounts of heat into their rooms and color or flavor the inputted signals in some preferred manner.  This group is typically and understandably seeking a more electrically efficient amp that doesn't raise the temperature of their rooms but still performs at a high level.
      The 'something missing in the sound' they have difficulty pinpointing is predictably the coloring and flavoring of the inputted signals that is avoided by design by most good class D amps in favor of a much more neutral approach that emphasises faithfully amplifying inputted signals more attuned to the audio ideal of an amp as 'a straight wire with gain'. I have no issue with this group preferring their more colored amps.
     Of my 3 general groups above, I agree that group#3 is definitely the most frustrating since they offer no scientific evidence of support because none exists, are very vague about the sonic manifestations they theorize exist in the audible band due to the switching frequencies being too low and I'm not aware of a single experienced class D user/owner, including myself, who has ever heard any sonic anomalies that they claim exist.
     I think it's safe to state that any logical person would consider their theory as being thoroughly and completely debunked.
     Just for fun, however, let's assume they're correct and all the thousands (millions?) of very satisfied class D amp owners/users are wrong.  Let's assume these sonic anomalies actually do exist in the audible range due to switching frequencies being too low. 
     If this was actually the case and the truth,  I would expect medical experts, neurologists and hearing care specialists to inevitably classify the ability to hear sonic anomalies in class D amps as an auditory/cerebral affliction, malady or syndrome. Just the fact that the majority of humans are incapable of perceiving these sonic anomalies but a small minority of the population can indicates an allergic reaction to class D by this minority. 
      I agree that individuals in group#3 can be extremely frustrating and annoying. But perhaps we should be more sympathetic to these poor afflicted souls.  Just as being lactose intolerant prevents those afflicted from enjoying a delicious glass of cold milk, being class D intolerant prevents those afflicted from enjoying the delicious sound of a good class D amp.

Love,
 Tim 

" IMHO I find class D amps to be less musical then Class A amps. I tried several class D amps and to my ears they lack the midrange, rhythmic
space, texture, air and less involving compared to good Class A amps.Something just seems to be missing musically to my ears. But to each his own. I'm not a audiophile snob I just know what makes my finger snap, head nod and foot tap."

Hi bluesy1,
     I understand.  I think it's a good and healthy thing that there's such a wide variety of amps currently available that individuals can tailor their system sound by choosing an amp that matches their sound preference.  
    Sound preferences are as unique like fingerprints and snowflakes.
    Your snowflake, bluesy1, seems to fall into group#3 from my last post.
     I'm glad you found a system sound you prefer with your class A amp.
Enjoy,
  Tim

" It's interesting how some defenders of Class D amps go to such lengths to classify the critics of these amplifiers as a minority, yet then go on to claim that the critics are prejudiced. Hmmm ...  "

Hi cleeds,
     Sorry, I'm not understanding your point.
     I really didn't go to great lengths to classify the class D detractors I've  read responses from since I became interested in this technology about 5 years ago.  Just a few minutes recollecting, a few classifying those I recall from Audiogon and other forums and a few minutes detailing my thoughts.
     In retrospectively considering and gauging the totality of posts I've read about class D in the past 5 years, I have little doubt that supporters of class D are in the majority and detractors in the minority. 
     I have no doubt that various forms of bias were evident in many of the class D detractors' posts.  Here are some of the major forms of bias I recall:
1.  Bias in the form of claiming class D was only good enough for subs even though they'd never auditioned a good recent class D amp in their system. 
2. Bias in the form of claiming their current amp would outperform a class D amp even though they'd never actually auditioned one in their system.
3. Bias in the form of claiming the majority of class D amp's switching frequencies  were too low and negatively affected sonics in the audible range even though they provided no scientific or even anecdotal evidence to support their claims.
4. Bias in the form of claiming class D amps were inferior because the Damps they auditioned in their systems failed in their opinion to outperform their much more expensive tube or class A existing amp.

    There are more forms of bias I recall but I'm short on time right now.  
    Yes, I do consider class D detractors overall a minority and do consider many of their posts I've read over the past 5 years to be biased in some form.
   Your stating this and adding a "Hmmm..." does not amount to a coherent statement.  Please clarify.

Thanx,
  Tim   

 "If bias was a disqualifier, these forums would be dead quiet."

Hi mapman,

     Good point. I agree that most of us, including myself, have developed biases along our audio journeys.
      I view my bias in favor of class D as based on research and personal experience using these amps. But I also realize that, in the end, all of our personal and particular biases are just our opinions.
   Rereading the previous 6-8 threads, I think the thread topic took a turn for the worse toward a discussion of bias and prejudice when I posted stating I liked the way erik_squires had characterized those claiming the switching frequencies used in most class D amps as being too low. This is erik's comment:

" It is the notion that Class D switching speeds are the cause, and that someday they'll be fixed that irritates me. It's a type of prejudice not born in evidence. It's the equivalent of "all feedback is bad" sales pitch for some amplifier designs."

I then posted my response below:

""Hi Erik,
     'A type of prejudice not born in evidence' is a very accurate and succinct way of describing how some class D detractors have a knee-jerk response, whenever class D is mentioned, of proclaiming a completely unproven theory that current class D switching frequencies are too low and negatively affect frequencies in the audible range."

     I thought that would be the end of discussions about bias and prejudice. However, cleeds than posted the following post responding to my post:

" It's interesting how some defenders of Class D amps go to such lengths to classify the critics of these amplifiers as a minority, yet then go on to claim that the critics are prejudiced. Hmmm ... "

     I found the point of cleeds statement above to be undecipherable and responded with a post asking him to clarify. In retrospect, I think I made a mistake posting my response since you responded to my post before cleeds responded to clarify.
   , I think your response of: " If bias was a disqualifier, these forums would be dead quiet. " was completely appropriate and accurate since my response standing alone, without a response from cleeds clarifying his point, just seems like me ranting about class D detractors' biases.
     I regret having to write this difficult post but I think it was important to clarify the sequence of responses to explain to readers of this thread that it was not my intent to turn the discussion toward the subject of biases and prejudice. My original intent was to complement erik_squires on his post, that succinctly and accurately described the efforts of a few class D detractors to claim switching frequencies are too low, when he stated " It is the notion that Class D switching speeds are the cause, and that someday they’ll be fixed that irritates me. It’s a type of prejudice not born in evidence." Subsequently, it was my intent to have cleeds clarify the point of his post, which I hope he will still do soon.

     I hope this post clarifies things for all.
     In conclusion, I just want to state that, although I currently use class D amps and have admittedly developed a favorable bias toward or opinion of them, I don't think they're right for everyone and I know that others have developed a favorable bias toward or opinion of other amplifier types. I think that's just the way it should be.

Sorry about the confusion,
     Tim  

Mapman,
     Your last post was an excellent summary of the current state and future possibilities of class D amps.  I agree with all of it.

" I don't know why people have to defend or overly praise Class D compared to other amplifier topologies when the end result is if you like it then keep listening."

Hi sfseay,
     While I generally agree with you, I think many readers of these class D threads are considering trying one of these amps for the first time and base their decisions largely on the impressions of people like us who already have experience using them in our systems.

     I know I was reading class D threads for this purpose when I first began considering trying a class D amp about 5 years ago.  
     But that was an earlier time in class D's evolution and, as I recall, there was a more even balance between praisers and detractors at that time.  If I'm not mistake, I believe mapman was one of the early adopters praising class D but there were also many claiming class D would never be a good choice for anything other than a sub amp.
    I finally just decided to try one and decide for myself how the current good examples of this technology performed in my stem.  I thought it'd be more useful to start developing my own experience with class D amps than to rely on others' impressions.  I was thinking just as you stated: If I liked it then I'd keep listening.  
     Perhaps what you consider irritating and excessive praising of class D is just considered useful positive feedback to some still considering whether to try one of these amps in their systems.

Tim

Hi scott_w,

Congrats on your soon to arrive DAC amp. You're fortunate you were able to audition 2 different class D amps in your system before you purchased. Typically, you’re required to purchase the amp and then audition it during an in-home trial period. But I suspect companies have a very low % of amps returned through these programs.
You named 2 of the 3 main common sonic qualities I’ve experienced with good class d amps: a very neutral flavoring and effortless dynamics. The other main sonic quality that is typically clearly evident in good examples of class D amps is how quiet they are. Music seems to emerge from a dead silent background that seems to enhance the musical impact and details perceived.
Welcome to the Great Sounding Green Amps Club.
Please post back with your impressions once you’re able to audition for awhile.
Tim

" This is all great discussion but doesn’t it come down to your ears, budget  and preference for the love of music."

     Yes, bluesy41, it does all come down to what equipment enables one to most enjoy reproduced music in their rooms based on their ears and budget. 
     I think it's generally known and accepted that great sounding systems can be assembled using tube, class A and the best class AB amps.  But these amps are not only very expensive they are also very large, heavy, electrically inefficient and emit a lot of wasted energy in the form of heat.  However, nobody can accurately claim that they don't sound very good.
     An underlying theme of this thread has been the revolutionary and egalitarian nature of good class D amps.  More Individuals are now able to attain 'hi-end' sound quality at an affordable price.  The fact that these amps are relatively small, lightweight, electrically very efficient and emit little heat are all just additional benefits to the very good sound quality
    In the not very distant past when good class D amps didn't yet exist, those not able to afford the steep price of the best amps were limited to finding an affordable class AB amp they liked.   It still comes down to your ears and budget, class D has just expanded everyone's options. 

Tim 

Hi riskymichael,

     I've never had the pleasure of listening to the Rogue Sphinx integrated amp but find it very interesting because of its combination of a tube preamp section with a class D amplifier section.that uses a traditional toroidal power supply rather than a smps (switch mode power supply) like typical class D amps.
     As many class D amp users, including myself, have already stated earlier on this thread, the combination of tube preamps with class D amps has resulted in exceptionally good system performance with a broad range of both tube preamps and D amps.  I can attest to very good results pairing a VTL 2.5L (the standard Chinese tubes being rolled to a set of NOS Mullard tubes) with my first class D amp, a Class D Audio SDS-440-CS that was my main amp for a few years and also has a toroidal power supply. 
     Obviously, Rogue is well aware of this synergy of tube preamps with class D amps and it's likely a major reason why your Sphinx sounds so good.
  
     The subject of whether there's a performance benefit to using the more traditional toroidal power supplies rather than the newer switching ones in class  D amps is less clear.  I now use 3 class D amps in my combo 2-ch and ht system, 2 stereo amps with toroidal power supplies and a pair of mono-blocks with the newer switch mode power supplies.  I notice all have the usual class D attributes of very low background noise, low distortion, high detail levels from top to bottom, very good dynamics and being very accurate and neutral overall. 
      The mono-blocks are more expensive,use different class D power modules and are much more powerful than both stereo amps.  I do notice the monos are even more detailed, even smoother and more life-like in the mid-range/treble and portray a more solid and stable soundstage illusion which I attribute mainly to the different class D power modules.  I also notice the monos have more powerful dynamics, especially on better 24/96Khz files recorded direct to digital, which I mainly attribute to the significant increase in power and perhaps the power modules and smps, too. 
      However, I'm unwilling and unable to claim whether the difference in power modules or power supplies are responsible for the clear improvement in dynamic range of my mono-blocks. 
     Without comparing otherwise identical versions of our amps, one version with a toroidal and the other with a switch mode power supply,  I don't think we can determine which performs best. But even this comparison would not address the relative degree that the power modules and power supplies affect amp performance.  
     The only things I can state with certainty is that my smps monos are more efficient and run cooler than my toroidal stereo amps. 
 
 Tim

Hello listening99,

     I’m not quite sure who you’re directing your question to.  If it’s me, I don’t think I’m the best individual to answer your question.       My experience with class D amps has mainly been searching for ones that best drive my former Magnepan 2,7QR and current Magnepan 3.7i main speakers, which are both only about 86db@ 1 watt and much less efficient than your 98db@ 1 watt Tekton Moabs.     The best amp I’ve ever used on my speakers are a pair of D-Sonic M3-600-M class D mono-block amps.  But these amps output 1,200 watts into my 4 ohm speakers, which seems excessive to me for your 4 ohm speakers.     Unfortunately, I have no experience utilizing high efficiency speakers since I was 18, 44 years ago. Therefore, I have very little useful knowledge to share with you except I believe you don’t need to exclude any amps or amp types from your search. Hopefully, you’ll receive some other lower power suggestions from other readers of this thread,  
Tim
     

jwincville22,

You’re likely getting no responses to your request for sound quality reports on the 2 newer 52X and 54X ATI class D amps because you’re only reaching members who own one of these specific amps AND happen to still be following this long running thread. You may get more responses by starting a new separate thread.

Sorry, I’ve never auditioned any ATI class D amps but I can verify that the D-Sonic M3-600-M class D mono-blocks I own are excellent amps.
However, I bought mine about 4 years ago when they utilized Anaview/Abletec ALC1000-1300 class D amp modules. Anaview discontinued the ALC100-1300 modules in 2014 and I believe the current D-Sonic M3-600-A monos utilize the newer Anaview AMS-1000-2600 modules. I think D-Sonic only uses Pascal modules in their top of the line M-1500 mono-blocks.
Both Anaview and Pascal are Scandinavian companies and their class D modules differ from most by combining the amp section and the switch mode power supply (SMPS) on the same board. Most other class D module design/manufacturing companies, such as Hypex-Ncore and B&O-Ice, offer the amp sections and SMPS as separate products on separate boards.

I asked D-Sonic’s owner, Dennis Deacon, back in 2014 about the sonic differences he noticed between the Anaview ALC-1000-1300 and AMS-1000-2600 modules and here was his response:

" Tim,

I have been shipping amplifiers with the new AMS1000-2600 modules. The sonic differences with the previous ALC1000-1300 are very subtle with most source material. They do have a more natural resolution of detail and a more natural impact in the upper bass to lower midrange area. This is where most big dynamics are heard such as percussion, cellos, baritone and bass horns."

Here’s the name of that thread that you might find useful and interesting:

D-SONIC SOA Class-D Core Amps. The best Class-D ?

Tim

georgehifi,

There’s a vast number of class D amp owners literally throughout the world that have absolutely no doubt about whether their amps are extraordinary performers in their systems. Yes, the great majority of them have switching frequencies in the vicinity of 500 KHz and may not possess the latest and fastest FET transistors in their output stages. Most of them are probably unaware of this but likely wouldn’t give a hoot if they were aware because they sound so incredibly good in their systems.
The owners of one of the many current or recent crop of extremely good class D amps just hear the obvious; their amps have very low distortion levels, dead-quiet background noise levels due to very high signal-to-noise ratios, excellent frequency response throughout the entire audible range, very good dynamic range, very good channel separation along with the ability to handle very low speaker impedance levels and deliver more than enough power to properly drive any speakers.
Additional class D amp benefits include small size, low weight, high electrical efficiency that results in low electricity consumption and very little excess heat and all at very affordable prices. What’s not to like, right?
Despite all the benefits of good class D amps described above, you continue to suggest avoidance of these amps until they utilize switching frequencies in the mega-Hz range and the latest and fastest generation of super-fast FET output stage transistors .
Will higher switching frequencies and faster FETs enable class D amp performance to get even better? As a user of several exceptionally good class D amps of recent vintage, I find it somewhat difficult to imagine how their performance could significantly be improved but I’ll keep an open mind until I give one a good listen in my system.
Until then, however, I. would advise anyone considering a class D amp that it makes little sense to wait for possible class D amp perfection.
Nobody needs to deprive themselves of high quality sound by making the same mistake that georgehifi consistently and inexplicably insists upon: making perfection the enemy of the extraordinarily good.

Tim

celander:  " I suspect some type of class A-class D hybrid will likely be the future for all class D topologies."

    There are currently class D amps using the topology of both transistor and tube analog class A input stages combined with analog class D switching power amplifier stages. 
      I've never auditioned any of these amps but did read a very good professional review on 6Moons about the French DeVailet solid state hybrid integrated class A-class D hybrid.amp.  The reviewer loved it but it was uber-expensve like most of the best traditional amps are and always have been. during the past century and possibly for another century.
     Perhaps the most significant  aspect of the many good class D amps is their affordability.  From my perspective, the egalitarian nature of class D technology is a beautiful thing, bringing extraordinarily high sound quality to an increasing number of individuals' systems that otherwise would not be able to afford and experience it.
     I'm hoping the future of class D topologies is a bit more interesting than just relatively expensive hybrids.  The inventor/designer of both Ice and Hypex NCore  class D amp module technology, Bruno Putzeys, has stated he's able to design class D amps that sound like any traditional class A, tube or hybrid amp topology desired.
     I wonder if he could design an affordable class D amp that could mimic the sound characteristics of the best current and past examples of traditional amps, along with the best example of independent class D amp sota efforts, that is user selectable. 
     A guy or gal can still day dream, right?

Tim

Hello listening 99,

     There are certainly several excellent class D amp bargains currently available for attaining very good performance at very reasonable prices. It sounds like you just purchased a prime example.
     I’ve owned and have heard a wide variety of class D amps in the past 10 years and I’ve noticed some come common qualities shared by the entire group regardless of price. These general qualities are very solid and taut bass, very low distortion, an extremely low noise floor, very good detail and a very neutral overall sonic presentation, with seemingly nothing added or subtracted from the inputted signals.
     I’ve found the most obvious benefit of the better, and more expensive, class D amps is the quality of their mid-range, treble and holographic imaging abilities.
     Currently, some class D amps rival the performance of the best amps available, regardless of amp type. Unfortunately however, the prices of the best class D amps also rival the prices of the best traditional amps.
     Because of this, when I felt the urge to upgrade, I decided to restrict my budget to an amount I could afford but also decided not to restrict my search options to a particular amp type. I still thought a mid priced class D amp, a pair of D-Sonic M3-600-M mono-blocks with Scandinavian Abletec power modules for about $2,100/pr, performed best driving my speakers. I also knew for certain through in-home auditions, that this was thousands less than comparably performing traditional amps.

Tim