My NAD 3020 D proves your Class D tropes are wrong

Just a few cents here.  Class D seems to be one of the many technologies that some folks just won’t allow to grow.  No matter how much development goes into it, there’s gonna be those that will never accept it as producing quality sound.  NAD being a company that has cut its teeth on producing very good sounding equipment over many years gets reduced to junk just because they use a historically unpopular technology among audiophiles in a new age product.  Something’s clearly amiss here.  

I've been listening to a vtv purifi eval-1 for just over a week on my ascend acoustics towers being fed with a topping d90 dac using the topping a90 as preamp.  I'm mostly very impressed.  It sounds super clear and punchy showing off on great recordings. 

On the other hand bad recordings sound exactly how they sound but clearer.  Purifi gives you the truth and nothing but the truth for better or worse as far as I can tell.  I think the only way around this is for somebody to invent a DAC with powerful AI that can remaster bad recordings on the fly in the most euphonic way.

It is quite possible there is a flaw in the ICEPower design where optimum operation requires a higher operating temperature. Many SS parts have significant performance change w.r.t. temperature.  I would say run them hard for 20-30 minutes after cold and see what you think, preferably with you out of the room so you are not getting desensitized.

Technics is the curious case of feed-forward design. :) Kind of sort of.

It depends on which part of their website you're paying attention to :)

Are you working on any Class D amps?

Yes. Its one of our own design- we're not using anyone's modules.

Hey atmasphere,

Are you working on any Class D amps? 

Kindest Regards,

Technics is the curious case of feed-forward design. :) Kind of sort of.

Class D feedback works so differently than linear amps that I have trouble believing the amount of feedback behaves the same way, but what do I know?

As far as I know, feedback is fundamental to Class D. It simply can't operate without it.

@erik_squires You are working with a misconception! You can (and some do) operate class D amps without any feedback at all. Up until a year or so ago, that was how all our prototypes worked. Feedback isn't used to construct the output of a class D amp, and you can have output with no feedback. IIRC the Merill class D is a zero feedback design; Technics claims that their amp is zero feedback too.

How so?

As far as I know, feedback is fundamental to Class D.  It simply can't operate without it.  Take a look at online documentation for how a triangle wave and the incoming signal are compared, and feedback is used to construct the ouptut.  The only real choices are where you take your feedback from.

Without feedback there is no output.

Class D feedback works so differently than linear amps that I have trouble believing the amount of feedback behaves the same way, but what do I know?

How so?

I've had many Class D amps over the years, Hafler, NAD, Mcintosh, B&K. They all sounded good. I actually miss the B&K. I also had some Pioneer, Marantz, Denon and Sony amps/receivers which all sounded horrible. I even had a Hitachi Class G which actually sounded quite good.
But I finally did try a Class A (590AXII Luxman) and I can never go back to Class D. I'm not bashing D, just saying that A has been a big improvement over every D I've ever had.

The class of operation isn't important. How much feedback the amp uses *is*. This can have an enormous effect on how much and what kind of distortion is present.

Class D feedback works so differently than linear amps that I have trouble believing the amount of feedback behaves the same way, but what do I know?

And that is the difference between a technician and a scientist. With the exception of Floyd Toole who hangs out there and I have the deepest admiration for, they are technicians pretending they know a thing about science when they don't.

Nelson Pass, Revel, Bose, JBL, Meyer Sound. That's where t he actual scientists are. I don't necessarily like the result of all of them, but their science and business practices are rock solid as a result.

Na, you just have to know who exactly you are dealing with. There are a ton of tire kickers there, but also some people really strong, especially on amplifiers and electronics, and digital.  Acoustics is pretty weak, but that is pretty true for most forums.


I don't see Nelson at all as a scientist. Tinkerer and artist perhaps, but not scientist. Bruno Putzey is far more of scientist, as is Dr. Bose, and not just because of the Doctor, but the company overall. Certainly some scientists at Harmon (Samsung) and I would put Meyer far ahead of Pass too.

All musical instruments can be defined by their unique spectrum of harmonic overtones.  Harmonics are what enable you to distinguish between a viola and a clarinet playing the same note, e.g. A at 440hz.

Amplifiers running in any class, e.g. AB, will not have the same amounts and combination of second, third, fourth, etc. harmonic distortion.

I do not believe you can hear any difference in normal home listening from equivelant models with A/B power.  

The class of operation isn't important. How much feedback the amp uses *is*. This can have an enormous effect on how much and what kind of distortion is present. Distortion is a good deal of the reason we hear differences between amplifiers- that old trope about 'distortion is negligible and therefore inaudible' so often seen in reviews of the last 50 years is false.

For a serious 'home' listener on a budget this discussion becomes a little prissy.  The ranges of difference make very little in a normal home's rooms and rooms under 16' x 16'.  The higher ranges of my amplifiers have never even gotten close to max, whatever the 'Class'.  They would blow ear drums and windows out first!  
One of my daily amps today is the Peachtree Grand X-1 hybrid integrated with valves in the pre-amp stage and 440 watts into 8 ohms.  The big watts are from a Class D amplifier.  The parameters I look for in an amp are more than ample with superb all-around performance.  Especially the onboard ESS Sabre DAC and the tubed pre-amp's handling of all forms of digital source material.  I run only a coax from my CD unit and even that sounds really good being processed in an integrated amp.  Sorry, no mono-blocks or ICE power.  
I have seen the reviews and gone off ready to 'move up' with a Mac MA252 valve pre-amp and solid state Mac A/B power too. and then the Prima Luna all tube designs which are awesome indeed.  And then I sit down in my listening place and listen to a lot of vinyl, CDs and FM radio with great Public Radio stations (shout out to WCMU on line and the 8 PM EST Sunday evening with the Duke of Juke blues show and the later turn to  blues).  Oh, oh.  I think some of this group may have passed out when I said 'FM radio'.  I hope they enjoy their monster systems as much as I enjoy this Class D that is made very well, even if not driving noise at a fraternity party.  But this 440 per channel would blow the place up without distortion and lots of play.  
I believe the entire Peachtree amplifier NOVA series that run up to 500 watts per are loved by their owners and all Class D.  And as many others have rightly noted:  I do not believe you can hear any difference in normal home listening from equivelant models with A/B power.  

I’ve been buying, listening to and selling/swapping class A and A/B audio gear since 1974. Last year I downsized and so needed to simplify the space and reduce the number of ’boxes’. So I sold off my large monoblocks, preamps, DACs, subs and large floorstanders. Bought a pair of Goldenear Triton Ones (class D powered bass units in each). This was my first introduction to class D - very happy with the sound. Last month my NAD M33 arrived (Class D again - this time by Bruno P.) and to say I am happy is an understatement. In my room they are a wonderful, clean, emotional and tonally rich combination with a great synergy between amp and speakers - definitely no nails scratching on a blackboard. These are all keepers.
I have never heard older class D models in stand alone power amps so cannot comment on them, and even if I was able to, my views would be entirely dependent on the combination of components used and room they were playing in.This particular class D design and configuration is a game changer fro me.

Blaming on Class D in general is just a nonsense. It is not a matter of a taste, rather it is an objective reality that there are quite affordable class D amps that  sound better than many more expensive class ab amps  in terms of all objective sound characteristics. Point. Just as an example, according to my experience, I consider it  is not easy to find a class ab amp that sounds as good as my Cherry Megaschino Class D amp.
Wake up guys!

@yyz hoping that is a Rush reference...

Best band ever!

Please do us a favor and listen to some Purifi amps.  Seems like UPS is delivering to you every day.   Hope to be like you in the near term.......

I'm going on 15 years of DIY Class D,  all Hypex stuff way back to their UcD.  

I spent way too much money on Class A, A/B, Tubes with the all the usual suspects....Levinson, Pass, Rowland, Mac, etc....

Finally figured out that a great source (streaming - Roon - Qobuz) gives me the most enjoyable (maybe not the best) listening experience to date.

I'm leveraging a Ravenna interface thru Roon and the fiber connectivity is absolutely tremendous.

M

Interesting comments on burn which for the most part was needed in all my amps, except the Benchmark AHB2.

I recently bought the Class D D-Sonic M3a 800s stereo amp for my Thiel CS3.7’s and the owner of the company told me that his amps do not need burn-in. I tend to believe him on this. These amps use Pascal modules. I like them, especially for the price ($1500). I am currently running them DAC direct to amp (Gustard X26 Pro) and will add a CODA 07x preamp, that is if the UPS driver decides to make their deliveries today.

In the future I will likely get the CODA #8 amp but this D-Sonic is very good.

Class D?   I have heard PS Audio's Class D amp.   Sounded very good with better detail I have heard with tubes or class AB.  This one sounds even better!

https://www.hifi-advice.com/blog/review/analog-reviews/amplifier-reviews/nuprime-st-10-power-amp/

NuPrime ST 10

I can't imagine that system is that good.  However, I do not make rash judgements about anything without personal experience.  The fact that you say because you like it it must be exceptional means nothing to us if we cannot hear it.  I am glad you enjoy it.  That is all that matters.

@dave_b

What exactly is your problem? I mean it both existentially and with your inability to use full sentences.

You don't like the thread? You don't like the posters?  You can't contribute so you have nothing to say worth typing?

Still desktop stories...😳  Op Amps 😬  oh my 😱

I formerly agreed with Teo, but after getting a VTV amp with the Purifi module and the Sparkos op amp, I am truly impressed with the sound in my system.  It sounds neither warm nor cold, but reveals an amazing amount of information in such an utterly clean fashion.  Same with my impressions of my friend's NAD M33 integrated amp, which has the Purifi module as well.  Both operate as cool as a cucumber.  I am being made a believer, in spite of my dislike of early Bel Canto, Red Dragon, and Nuprime Class D amps... which sucked the life out of the music.  
This is a quote from a well known speaker manufacturer who will remain nameless, but I trust his ears, because I am hearing the same thing he is:  

"Yes, I have read and heard many good things about the Purifi amp modules. Maybe I'll try them. I have been using the Cherry amps which are very good class D also. This technology will eventually push AB amps out of the market."  

Class D technology has arrived and is ready for prime time and with the Cherry, Apollon, and VTV amps, it is very affordable.   If you have the enough coin of the realm, I suspect the new Merrill Class D amps would be incredible.  The GaN technology is on the cusp of a new era in amplification as well. 

I kind of backed into class D amp’ing when I set up my 1st real desktop audio system w/discreet DAC in this home office ~2008 (after years of 2.1 "computer systems" running of a soundcard). There’s no room on this crowded desktop for class A/B or tube amps.

I really lucked out: the class D amp I bought was Wyre4Sound’s ST-500, which I use on its side to save space (got the blessing of Wyred4Sound before doing that). I paired it with a very revealing passive monitor (ATC SCM12 Pro) and the sound was excellent. Have had 2 other high-end 2-way passives here since then (Aerial Acoustics 5B; and vintage KEF 103.2). All sound very good w/the ST-500.

I will eventually upgrade to more current class D technology. I lean toward Nord Acoustics hypex-based stereo amp that allows use of Sparkos op-amps (I’ve used them elsewhere & know how good they sound). But if I trip over a gently used Cherry stereo, maybe that...

I'm using one of these:

https://www.ebay.com/itm/50ASX2-2-Channel-Power-Amplifier-Module-2x50W-HiFi-Power-Amplifier-For-ICEP...

Sounds perfectly good to me.  

I didn’t even know what a class D amp was and as it turns out I had already owned 2, for years. I owned 2 ICE amps that powered my power sound audio subs designed and built and sold by Tom Vodhanel of PSA.

Funny thing, he sells a ton these ICE powered subs and the owners of his subs are amazed by the voicing or tuning of his subs and quite a few have expressed that they sound better than the SVS line of subs with MOSFET
amps.

What I’ve found out is that it’s the design skills of the designer that matter the most in designing gear no matter what he or she decides to use. Many designers go about in many different ways to get the best sound they can get. The quality of sound coming from a component is not based on the fact alone that it is a class A or A/B amp. It’s the designer. There are good amps made in every configuration and bad amps made by bad designers.

The NAIM Atom is one heck off a LiL Mulekicker, sounds better warm...

I agree, some topology and combinations of components just need warm up... The Ayre VX-r a great case in point,, Ontrak semiconductor version took days...leave it on ! The twenty w Diamond circuit was golden after a few minutes....twenty.

D shows promise,IF people have an open mind....ears, perhaps both

I find myself less willing to type with the same precision and care that I used to.

I get accused of being overly specific more than I used to...

hi @atmasphere

You are totally right in calling me out here:

@erik_squires I missed this earlier. This is not true of all class D amps.

I meant to say, I’ve heard it from several ICEPower amp owners as well as my own experience that these amps get cold for days after being turned off. THey are fine being switched on/off daily for HT use but for 2 channel use and stereo the can be glaring until warmed.

I find myself less willing to type with the same precision and care that I used to.

@kren I didn't know about this product. My experience with CA is that their amps are a little too forward for my liking. I found them powerful but fatiguing. Interesting they are going to class D. I can't imagine they will do as good a job as NAD and can't see this unseating the naim although it is competitively priced. It remains to be seen but based on what I know about those 3 companies CA may have to lower the price point. 

Yeah some take just 15-30 minutes.

Cambridge Audio just released the super integrated (includes built-in streamer/dac - ESS 9016km2 or 9018km2, StreamMagic platform) EVO super integrated amps for $2250 and $3000 depending on configuration. Use Hypex nCore class D amp modules.

Will compete against the NAD M10 nCore superint that goes for $2750 and class AB Naim Uniti Atom for $3300.

I wonder if these Cambridge are competitively priced? Maybe a bit high? TBD I guess

Going along with that, there is something about some Class D that requires DAYS to warm up.

@erik_squires I missed this earlier. This is not true of all class D amps. I'm not contesting that this is your experience with your amp, but its nothing to do with class D- its something to do with your amp.

Enjoying mightily my week old D 3020 V2. Sounds delish. I also own Tommy's Cherry amp. And a rebuilt Dynaco. Ergo, both ends of the amp spectrum. Anyhoots @erik_squires I'm with you 100%. To own one is to kick back & smile. 

I have four power amps: NAD M22v2 (Class D), PS Audio BHK 250 (Hybrid Class A), McIntosh MC 2600 (Class A), and Pioneer SPEC-4 (Class A).  My vintage Mac and Pioneer amps work well in my rec room, but not so much in my listening room.  In my listening room, I use the BHK with the NAD as my backup.  

The BHK 250 sounds the best in my main system; it is more musical than the NAD.  There is no harshness, and it is more detailed, has better imaging and sound stage, etc.  At twice the price, I would hope so.  

Having said all of that, the NAD sounds very good in my main system and in my rec room systems.  I could live with it if I had too.  Like the BHK 250, the M22v2 can be run in standby mode so it's quick to warm up.  I give both 30 minutes before doing any serious listening.  The M22v2 is OK by me.

Guess you can get used to anything after it’s been on long enough 🙃

I can always hear class d amplification because it is so tonally off that it is like fingers scratching on a chalkboard to me.

I just listened to a class D yesterday that was more focused and just as relaxed as a good tube amplifier. So I very much doubt this statement- it is trolling IMO.

Class D is used in most powered subs which is not to say it can produce high frequency well.

This probably depends on what is meant by 'very well'. I listened to two amps yesterday, one tube and one class D. They both have less than 1 degree of phase shift at 20KHz. The class D amp has over an order of magnitude less distortion than the tube amp at that frequency. But its primary distortion product is the 2nd harmonic, and enough that just like a tube amp the 2nd is able to mask the presence of the higher orders. So it sounds like a tube amp, although considerably more neutral owing to lower distortion overall and the ability to act like a nearly perfect voltage source.

But not all class D amps are like this. They have as much variance from model to model and brand to brand as you see in tube amps, which cover the gamut of SET, OTL, push pull triode, push pull pentode and so on.


The bottom line is you have to be careful about making blanket statements; in the world of class D as in almost any other topic blanket statement are so general as to be rendered false.

   I don't own class D but I heard the first generation Rogue Sphinx in a pair of Maggie 1.7s a few years back. I couldn't believe I was listening to a 1200 dollar integrated. Detailed, powerful, and warm. Could have listened all day.
   Tube pre and Hypex if I remember correctly. 
     It will be on my audition list when my current Tube preamp/class AB separates need replacing. 
      

I can always hear class d amplification because it is so tonally off that it is like fingers scratching on a chalkboard to me

I doubt it.

I can always hear class d amplification because it is so tonally off that it is like fingers scratching on a chalkboard to me.

I’ve never had a warm up issue with my 2Cherry...sounds the same if it’s been off for 2 weeks or on for 2 hours. 

I enjoy how Nelson tries different output transistors within his stash, in different circuits he comes up with in his head. Admittedly, 1 of 10 of those variations actually make it to production. He intentionally looks for rare or extinct opt transistor supplies to make it harder for people to clone his amps. Each variation and release sounding different from the past. Exploration never ends with him. Just gotta love it, rinse and repeat with new Opt's. All in search of a new and different variations of "sound" amplification.

I seriously doubt the majority of the self-proclaimed scientists over at the ASR forum have proper tools and platforms to measure all the various aspects of sound. Clearly many over there don’t use their ears much either, simply looking at graphs, charts, specs, produced by limited tools measuring only a few aspects of sound.

A fun read for those who appreciate the nature and physics of sound, so much more to it than a few metrics and specs used by techs too, have yet to see an audio lab covering much about sound https://physics.info/sound/

And, to your first point, silly me went over to the Audio Science Review (ASR) forum and started asking if "anyone" had tried pairing up a really good tube preamp with the NAD C298 Purify module based amp. Quickly realized all measurement extremists over there, few wanting to engage into "sound" discussion or anything with higher distortion.

And that is the difference between a technician and a scientist.  With the exception of Floyd Toole who hangs out there and I have the deepest admiration for, they are technicians pretending they know a thing about science when they don't.

Nelson Pass, Revel, Bose, JBL, Meyer Sound.  That's where t he actual scientists are.  I don't necessarily like the result of all of them, but their science and business practices are rock solid as a result.

Class D amps have traveled quite a long journey over 25+ years.
Surely, there has been a lot of focus on improving the technology.
I have been a dedicated tube guy for most on the past 50 years into this hobby. About to turn 68, got my first system when I went away to school at 18. BTW- it was a Pacific Stereo $199 special with the original Lenco TT. 25, or so, years ago I was thrilled with the Spectron, think it was, Class D amp. Believe it was the first. And even then I was excellent and had great qualities beyond tubes.
Noticed in the “recommended components” recently was the $50K Solution 501 mono blocks. Believe they are a type of Class D (switching power supply) with AB output. Has anyone heard them?
They must be pretty special...

Class D is used in most powered subs which is not to say it can produce high frequency well. But i do have a harman kardon receiver that is class D in one of my smaller systems and does very well with movies. If you want good clean power spend the money and get a mcintosh.

@jwl244 I am curious in your opinion and others in this forum...Is one possible reason we lean away from class D because of its distortion profile or lack thereof? My understanding with the best class D and purifi products distortion is really low.

Possibly. I find dedicated solid state class-A amp owners may tend to be more forgiving of traditional Class-D sound thinking about "heat" and "weight", and yet Tube amp owners not as much at first (maybe liking some distortion, with 2nd and 3rd order harmonics); however some hard-core tube amp owners may like the idea of rotating in another amp to spare their prized tubes on rotation, or like the idea of less heat over the hotter months of the year. Reasoning and conditions vary by individuals we can suspect. All a guess, I’m simply trying different things when I can.

And, to your first point, silly me went over to the Audio Science Review (ASR) forum and started asking if "anyone" had tried pairing up a really good tube preamp with the NAD C298 Purify module based amp. Quickly realized all measurement extremists over there, few wanting to engage into "sound" discussion or anything with higher distortion. Felt like a single alien against an army of thousands of pure scientists only focusing on measurement. Stupid me, I still want to try a really good 6SN7 tube preamp in front of a NAD c298 class-D amp just to see what happens.

A few great measuring amps and ruler flat speakers I’ve heard in my system were some of the most boring and non-engaging to my ears. Blame my room and/or blame my ears, the difference was notable to my ears. I like a little distortion in the right places.

Distortion: Something on that same type wavelength. I evaluated an ultra high-end solid state DAC a few years back, 125db SNR, amazing build quality, amazingly huge sound stage. Clear, smooth, deep in detail, yet it was one of the more fatiguing and un-engaging pieces of equipment in my particular system. Was kinda shocked. "All the notes, none of the music". Then one month later swapped back to my more distorted R-2R ladder DAC with a musically distorting tube and all the "music" and engaging layered three dimensional sound returned. Wallah, back to listening to music instead of listening to components. Recently heard a very nice higher $ class-D ice module based amp at a buddies house. He left it on for 3 days before I got there. I’m not sure if we agreed it was missing some of the harmonics. He later went with a dual tube R2R DAC, and it helped some however it is not able to produce a layered and 3-diminensional sound that I’m more use to. Smooth, somewhat musical, and 2-D at best. I think I’ve listened to class-a and tubes for too long and we all formulate our opinions on what sound good to us or perhaps leaning more towards the familiar sounds we started with or grew up with.

If you follow Paul @ PSAudio, hard core solid state guy for several decades since his time at Krell, recently accepting hybrid tube front-end BHK designs paired into their mosfet amps. Who’d a thunk, it happened. Then he opened up to Class-D. Who’d a thunk, it happened again. Even Paul reports publicly Class-D is going to be something to recon with (even more so), with added designs and development "over the next 5 years". I’m not totally "there" yet willing to continue to experiment as options evolve a bit more. Its exciting to see more rapid progress past 2-3 years with class-D, and eventually I plan to own a good Class-D amp. Looking for a great "keeper".  AGD has done some neat things... Also, kinda waiting for the right sounding hybrid design to surface. I’m betting we’ll see more coming from purist SS & Tube manufactures, realizing they have no choice now but to accept Class-D like PS Audio did, and doing well at it.

I doubt anyone on here has heard the new Legacy Amps. 1000 watts per in Mono blocks, 600 per in 7 channel. I have each powering up my Legacy speakers .. I came from ATI Signature series . It was their premier model. These Legacy V series class D's are better ...and cleaner, and quieter, and a lot cooler ...  

@decooney yes I've heard similar reports. I believe PS Audio burns in certain products before shipping as well. To be honest I'm not a huge proponent of burning in although your example would give credence to it. Not trying to get into a burn in or not thread.. I am curious in your opinion and others in this forum...

Is one possible reason we lean away from class D because of its distortion profile or lack thereof? My understanding with the best class D and purifi products distortion is really low. Maybe I'm wrong. On the end of the spectrum class A and AB products introduction more distortion but in a "good way" and this creates that "tube" sound so many audiophiles gravitate to. I'm not saying there's no class a or ab products without low distortion. I'm saying the distortion introduced by those products might be more pleasing to our ears. This is the departure away from measurements and numbers and just what we like to hear. Maybe there's more of the 2nd order harmonics if you subscribe to that. Class D might be too clean after all making those products sound clinical and unexciting. 

Going along with that, there is something about some Class D that requires DAYS to warm up.  Even after being used and on for months my ICEPower monoblocks sound like garbage after being left off for a weekend.

I have not run a binary search pattern to correlate time off vs. sound quality, but there have been about half a dozen other encounters with other audiophiles who have had this phenomenon. 

@jwl244,
"@decooney I wish I could say I put a ton of time in. I may have listened here and there for less than 20 hours total in a few weeks. I did not switch speakers in or out."

Good to know. Barely scratching the surface of end-game potential, possibly. I won’t name the company, yet the owner of a different Co started wondering why they were getting more returns than ever anticipated on a solid sounding product. After some in-depth internal investigation ,something very telling surfaced for this Co. They instituted a (3x) much longer pre sale/shipping burn-in process to these particular class-D products and components. The customer returns dropped radically after this process was introduced. Then they tell the customer to give it another 100-200hrs for the final 5%. Not all, but some higher-end gear benefits from longer burn in cycles, finally reaching a set point, optimum specs, bias, and maybe the type of sound we all look for. Its definitely worth giving a try in the future, fwiw. Good luck.