Class D Technology

Listen and decide. My Class D amps are the best I’ve ever had by far. They sound great always with most any speaker and that’s all that matters. Gotta match to right speakers for absolute best results though just like any amp.

Plus they are most efficient. That’s a good thing for amps just as it for speakers. That is really the thing that distinguishes them most especially for use with most any power and current hungry modern speaker that also tend to be smaller and more extended meaning power and current needed for best results. It’s a natural technical match that results in top notch performance in most cases out of a smaller more easily handled package which also means better sound possible for more people.  Of course personal preferences regarding what sounds best really is totally subjective and preferences will vary.

gdhal I think one of the things switching amps excel at is delivering power and current for very short periods of time which makes for excellent detail and transients. Its a very important aspect of music that often distinguishes great sound from just good. Power and current specs alone as published probably do not indicate an amps ability to deliver power and current quickly and efficienctly for very short periods of time when needed.

One way this is refelcted uniquely with the Class D amps I own and use compared to others is detail and articulation of the bass in particular. It is leaps and bounds more articulate and detailed than any other amps I have owned or even heard. When I first heard it, I was shocked thinking my bass was gone when in fact it had leaped to an entirely different level not heard prior.

My impression is tube amps tend to be a bit softer in this regard (which some may actually prefer) and class a/b SS amps often just miss it altogether.

Class A amps, tube or otherwise are historically the ones that probably do this best, but that is changing.....

georgelofi you are correct about switching frequency being teh key to even better Class D amps in the future.

Have you listened to any good quality class D amps or are you judging solely on technical interpretation?

Fact is the good ones sound very good today, as good or better than most. There is plenty of reviews and such published that support that.

I can vouch for it as well FWIW.

Thing is I am over 50 and do not hear to 20khz like I know I could when younger. So I am not the best one to judge what’s happening at the highest frequencies in detail.

In general, its something of a good thing not to be able to hear up to 20khz because there is often more noise and distortion at those frequencies than music.

Check the audio frequency music chart and one can see little music happens at the highest frequencies people can hear. It’s mostly "air". That’s part of music granted but since most audio involves a compromise of some sort, this is a reasonable one.

All I know is I cannot concretely fault anything in the sound I hear from my Class D amps with any speakers up to the task of handling all they can deliver. Most people would be thrilled with them. They are the quietest amps ever, with a totally black noise floor. At least that’s what I hear.

Also keep in mind if one is keeping score, Class D amps have the advantages of small size, efficiency and ability to drive most any modern speaker well, including smaller more extended models that are very popular these days.

Other SS amps can do it but are larger heavier and probably more expensive especially when power consumption per watt delivered is considered.

Class D amps are very "green".  Class A amps are "gas guzzlers".   That part is undeniable.

Tube amps generally require certain speakers that are an easier load and more efficient to shine. Otherwise we can be talking mid-fi results there as well. I’ve heard that on many occasions where speaker choice for tube amp is poor for various reasons.

So the only way its really a fair competition is to discount the sound quality of Class D, which anyone can do.

Then there is the fact that the Class D amps continue to improve as Glofi mentioned.

So Class D is definitely a player but the game is different from tube amps in that the speakers one ends up with for teh best hifi results will be much different.

" Right now the technology is to the point where the amps have become practical for mid fi, but they still have a ways to go before they can challenge a good class A transistor amp or a good tube amp."

Mid-fi?  That's actually a funny statement!

As for challenging others, people need to listen and decide.   All amps have technical issues and challenges.  Citing these and comparing does not tell you anything about which sounds best.

ricred,

That’s certainly a fair assessment. Everyone has their own personal preferences.

Mid-fi is not a fair assessment though IMHO. No amp is perfect. In that sense they are all "mid-fi" maybe. But I tend to think not. Each can only shine best when set up well and properly matched to speakers, etc. They are all the same in that way.

sean I think that is a particularly strong application for them that may be hard to match as cost effectively elsewhere.

I think they are also a fairly safe bet to be able to technically drive most any speaker well up to a certain volume depending on specific amp used. Meaning the ability to get teh most possible out of most any particualr speaker.

That’s not to say I would even think they always will sound best.

For example, I anticipate my Triangle Titus monitors, which are small but known to be very tube amp friendly, would sound better (within their limits) with a good SET OTL or push pull tube amp. I plan to try taht someday soon and see.

My Bel Canto amps do a great job of driving the Titus on paper technically, and still sound quite good together, but the sound is somewhat lean in comparison to the others. I have found that corner placement with teh bass reinforcement that offers does help a lot.

Also I would say that in general the best Class D amp demos I have heard over the years also tend to be with bigger and better more full range speakers that have no problem delivering flat bass to the lowest octaves when driven well.   That's one of the hardest things for any amp/speaker combo to do.  Just like Class D amps excel for use in Subwoofers, they also excel for use with speakers that require no separate powered sub to sound great when driven well.  

" What makes today’s class D amps sound cold and dry?"


I’d attribute it to the high damping factor in combo with the aforementioned transient capabilities.

Mine definitely sound best with speakers that like high damping. Usually larger ones with larger drivers that are inherently harder to control.

They are more towards the cold and dry on my little Triangle Titus monitors.

Not so on my somewhat larger and more extended Dynaudio Contour monitors or any of my other much larger and more extended speakers.

They are the cats meow on my largest the big OHM F5 series 3 floorstanders with much larger Walsh style driver often cited as benefiting from monster amps with high damping. That is very true!

I have two Class D amps. Bel Canto ref1000m monoblocs in my main system (with ARC tube pre-amplifier) and true digital Bel Canto c5i integrated in my other smaller setup.

They each sound way different. Both are "musical" but not in the same way. You should hear the c5i with headphones. It is quite spectacular. Plus it does all the rest extremely well to boot!

Mid--fi? I think not. I’ve heard a lot of mid and hi fi over the years. Both play in the bigger league for sure.  Kinda like the Cubs and Indians.  Maybe even the Yankees and Cardinals!

Ok George we get it.  You aren't sold on class d yet.  Others are. Mine sound great and no faults I could point to when listening.  They just make sweet music as said. 

George not much buzz on the new technics gear yet. Maybe to come. I was in their room at Capital Audifest but they kept talking about the gear and did not play it while I was there. I wanted to hear and was disappointed. Nobody had it in their best of show list that I’ve seen.

No doubt higher switching frequencies done well is better. How much better practically in regards to what can be heard is TBD. I will say that each newer generation of Class D gear does seem to only improve so not at the end of the road yet.

I try to hear these high frequency artifacts in my Class D amps that I’m supposed to hear and have not heard it yet. So if it exists it is not blatant. At least to these 57 year old ears.

Again there is often more noise at the highest frequencies human ears can hear than music. So perhaps its an error of omission mostly to the extent present at frequencies that really do not matter much for listening to music.

Take a look at the audio frequency chart and you’ll see what I’m talking about in regards to at what frequencies music mostly all occurs.

http://www.independentrecording.net/irn/resources/freqchart/main_display.htm

I recall when I was in college I could hear well to 20khz. I know because I ran tests.

I also found it much harder to get sound that was not fatiguing. This is back in analog days even.

These days I know I cannot hear to that extent which is normal for ears my age. I find listening not fatiguing at all and can listen enthralled for hours and not want to stop. With most any kind of music or recording. Well except the occasional really bad modern loud pop mp3. That’s what its all about. Maybe there is some advantage to getting older after all.

Any young cubs out there still with golden ears out to 20khz? I’d like to be able to associate what people like to listen to with their age and measured hearing  which becomes less extended for all as one gets older. I suspect a big correlation there.

Guido, thanks for the very practical and level headed advice. I suspect you have more experience with more Class D amps among others than most anyone, plus as far as I know you do not have any particular financial interest in any particular product line or type, so together that all means a lot.

I agree amp type alone means little. Its all in the execution as usual. Not just of the amp but matching system as a whole. There are many options of all types, some better than others and all surely somewhat different. Its best to understand something about them all and then decide. No one type will likely ever own 100% of the pie.  But I suspect Class D will continue to own an increasing larger slice over teh next few years anyway.   Who knows what might come next after that?

Yes Ralph sorry to hear that and best wishes for a fast recovery.

Right now I am listening to Neil Young Live at Massey Hall1971.   I am there!   Midfi has come a long way!   😌

Wow glad we're 11 years later now.

When relating impressions of various class d amps it would help to also mention what speakers were involved.

As I mentioned earlier Clas D will distinguish itself with certain kinds of speakers whereas with others it a harder call and some they will just not shine. Nobody is saying they will always sound best rather they up the game in terms of what is possible out of a package more people might like but only if given the chance to do what they do best.

As I sit here totally enthralled with what I hear coming out of my big Ohm Walsh speakers (12" Walsh style driver) as I am on most Saturday afternoons when I get a chance to have extended listening sessions I am totally baffled how some have such disdain for the technology. Something ain’t right.

Kijanki I think it’s easy to obsess on one or two aspects of a product, good or bad, and forget there are many factors that go into it many of which are hard to quantify and further there is no mathematical formula for determining how something actually sounds.

The more I read about it ClassD technology sounded like a good idea to me. My favorite local dealer sold only class d and tube amps. He had never steered me wrong over many years. These days he admits to me that the class d hybrid integrated amps he sells sounds the best with the choice speaker lines he sells and I would agree.

There are more than a couple highly regarded participants here that have accepted the technology as well.

Whatever. Everyone’s entitled to their opinion.

One correction is my dealer said he thought the class d integrated sounded best. Not that they were better necessarily. I chose the wrong words.

He sells mostly rogue and arc amplifiers and sonus Faber and Magnepan speakers these days.

It’s close minded to infer a product or technology is inferior or deficient just because one prefers something else. That’s all.  

I think a special niche for Class D, where it offers undeniable unique benefits that support better sound quality, is as a more practical  alternative to traditional big heavy expensive monster amps when lots of power and current is beneficial to drive certain speakers to their max.

That is what led to my foray into Class D. I got the 500 w/ch Bel canto ref1000m amps as my all out assault to drive my big OHm F5s to the max and that has worked out in spades.

There are other practical options in most other cases.

For example, the Bel Canto C5i 60 w/ch integrated I use on my smaller system does it all and the sound is the cats meow (very hard to fault) in that app as well, but there are many amps of many designs in the same power class that can work out just fine there as well. So not as clear a choice there. The C5i does have the other advantages of value (especially used), compact size and manageability, and versatility (includes dac and phone in a package smaller than a shoe box which also has the form factor to fit easily into the rack where it must live).

I would not expect someone who finds set sound to be most appealing to be allured by a Class D amp. It might approach the sound of a set if done a certain way but there is no value in replacing a good SET system with Class D if the SET checks all ones boxes. If volume/macrodynamics is of concern given SET amps low power output the solution is more efficient speakers, not a more efficient amp. A change in amp will likely trigger or necessitate a change in speakers and other things as well, a major ripple effect.

I would see merit perhaps in maintaining two unqiue systems with unique strengths and technical approaches, one SET and one CLass D or similar. That’s an experiment I have on my bucket list still. But frankly the C5i has worked out great and pushed that off for now a bit until such time I have ability or desire to pursue perhaps a third system just to see.

It’s just dead quiet ie very low noise floor seemingly. Not sure why or how. Its a characteristic of both my BEl Canto Class D amps, but is especially noticeable with the all digital C5i integrated (no tubes upstream).

A better analogy,at least in teh case of newer BEl Canto amps, is souping up the engine.

With ref1000m amps, they add custom input board for better integration with tube pre-amps and a beefed up powersupply board.

Original ref1000 was just vanilla Icepower in a nice box. I would not even consider using that with a higher output impedance tube pre-amp.

Just goes to show not all Class D is equal, even newer ones so gotta be careful about generalizing there.   

I do not hear that at all.

Be careful about taking a small sample and drawing conclusions from that on the whole. I’d have to hear the same setup others have heard this with, Only then could I comment on the sound resulting from that particular setup and compare to others.

I've heard the Pharoah Maggie pairing and thought it to be quite a good one.  I could live with Rogue Pharoah very happily.   Great product and good value.   

Composed is a great adjective that describes what I hear quite well.  

Class A particularly when no NFB used tends to have a somewhat warmer sound.

I have not heard Class D that I would call an inherent warm  sound, in fact not warm at all, however if a touch of warmth  is what one seeks a tube pre-amp upstream can help accomplish the goal.   The ARC sp16 I use with BC ref1000m amps does this to perfection through my very neutral sounding OHM Walsh speakers.   Tweaking of ICs and such can even make a useful difference here.

Hifi is like making soup.   You gotta toss all the right ingredients in the pot together to make it tasty for you.    Class D is a very good base to make your soup with IMHO.    Where it goes from there YMMV.

So if its not obvious by now the question has been answered repeatedly in some cases.

Some like it already and some not so much.

I’m on the like it side with Kijanki.

So its pretty much on par with everything else audio these days. Some like it and some not so much.

its nice to have choices.

The difference is Class D will only continue to get even better.

Someday soon everyone may agree.

Or not.....

Cheers!

There is absolutely no fatigue with the C5i driving any of my speakers including some that are documented to potentially lean that way with the wrong amp. 

George you conveniently forgot to mention some think the sound including the high frequencies are quite good and not flawed.  

Lets not selectively filter feedback just to help make a case.   

Im listening to my Bel Canto C5i Class D integrated with Triangle Titus speakers currently.  Other than the clean articulate bass I could easily think the amp was a very resolving and clean and dead quiet tube amp.  The treble is as good or better than most anything I have heard.  The sound draws you right in. 

So so let's stop trying to convince people the technology is flawed or does not sound good.   It's as good as anything these days done well.   Done well is the key like with any technology old or new.  

Murgesh what clas d setups have you heard? Why assume that what you heard is indicative of all cases? That’s called jumping to conclusions. My experience is the exact opposite of yours.


The c5i is in fact a digital Class D integrated amp ( not just class d). and the sound is nothing like you describe.

George im guessing you should be looking at specs and data of the Rowland amp not the ice module it uses alone. I’m pretty sure Rowland like others do things like beefed up power supply to achieve performance. Again I think you are selectively choosing your facts and data to support your case. Are you a lawyer? Many of these amps get rave reviews and are happily owned by many. Your technical case for why these must sound bad does not add up. Plus I can assure you the newer good ones done right are right up there. It’s ok if not your cup of tea for whatever reason. But that’s about it. If I had listened to the skeptics a few years back rather than drawing my own conclusions to take he chance I’d have maybe missed out on years of enjoyable music by now.   

57

The best reason to buy is that the good ones sound great even with harder to drive speaker loads due to lots of power and current delivery possible out of a smaller package due to efficiency.  

shibui,

Sounds to me like you pretty much nailed it in all regards based on actual experience seeking the best sound possible with some of the most challenging speakers to drive well ever.

That a Class D design can even compete in that arena says all that needs to be said really. There is no reason to categorically reject the approach. From there it comes down to personal preferences and case by case details that vary widely most likely. Plus things can only continue to get better as/if needed as bandwidth continues to increase over time. Better performance always tends to come for additional cost. class D is no different there except it lowers the price barrier for what most would consider good performance especially when more power is needed to get the most out of less efficient speakers. Ability to get the most out of more challenging speakers is the primary value added use case for Class D these days I would say though I find the newer ones to be top notch as well with easier load speakers I own. Class D has kept me from pulling the trigger on a tube amp now (and associated speaker changes that would be needed) for several years.

Power supply is no less important with class D than with other amps.   A lot of vendors focus on optimizing it and it is a common theme among better reviewed and received designs. 

Atmasphere why does 200khz bandwidth matter if there are no sources practically (record or CD res digital) that can even come close to delivering it today?

Seems like a purely theoretical argument.

I agree and have stated on many occasions that higher bandwidth alone is better theoretically all other things aside and Class D can still get much better there.   It certainly cannot hurt  assuming it is done well/right like most things.

But practically I am less sure. I expected my Class D amps to not sound nearly as good as they do given the theory. I’m glad I did not let that stop me from trying because it seems to be a non issue already practically, at least for me.

Thanks.

Assuming nothing is there to start with isn't a phase shift of 0 = 0?

I did not know vinyl has frequency bandwidth so high.    Most home hifi always talked of 20-20K frequency response.     Is this in practice or theoretical?   I'd agree theoretically vinyl could do more but practically its news to me.   The best digital (higher res) sounds as good as most vinyl to me these days.    RTR is better but look where that got us practically.

Also what is the math relationship between bandwidth and phase shift? Where does 10X bandwith number come from? is there something akin to Nyquist that is used to determine this? Did the engineers making high end Class D amps miss the boat on this somehow? it does not sound like they did in practice based on listening, at least the good ones seem to know what they are doing.

From my perspective there is understanding the theory which is useful and how things sound, for which there is no mathematical equation to properly represent that. Pundits focus on the strengths of a supporting theory and skeptics the weaknesses. No approach is perfect and holds all the cards. That’s clear by the variety of successful amplifier designs out there today.

Ralph sounds like you are actively prototyping your own class D designs? that tells me you think there is in fact something worthwhile there if done right.

Al, thanks for that.

I was aware of the phase shift concerns and recall looking at measurements and reviews prior to buying to get a feel for what is going on.   Knowing no gear measures perfectly in all regards I decided to give it a try and was glad I did. 

I have to say to whatever extent my amps and gear may be imperfect or not, listening enjoyment is not affected.  I can listen for hours and never grow fatigued or tired.   That's not something I could lay claim to with my system prior to Class D. 

So as we know  in the end it always comes down to what one hears and can enjoy or not.    Measurements help scope out the likely candidates in advance, and their technical strengths and weaknesses but never tell the whole story regarding how things actually sound.

So while nobody including me has argued that more bandwidth done right is always a good thing, I do still think its unfair to dismiss Class D technology and products as a whole these days based solely on that.   The benefits will far outweigh the disadvantages for many  but probably not so much for those who are put off for whatever reason.

I had a fellow agoner over to listen to my gear a while back. He is a fan of David Berning ZOTL amps. I heard these at CAF last summer and liked those very much as well. He indicated he really liked my setup running off the C5i which is latest and greatest Icepower and pure digital integrated amp as well with both phono and line level analog inputs. I do not know the bandwidth. Its a non issue in regards to what I hear personally so I haven’t even given it a thought. But I still gotta know so need to look it up. The ZOTL tube amps I heard and the C5i had quite a bit in common in regards to the sound IMHO. More evidence its the overall execution that matters more so than the technical approach of individual quality parts.

BTW has anyone ever noticed a reviewer complain about phase shift when reviewing gear at a show? They can find all kinds of faults but seldom if ever that. Are they not listening right or is it just not there? Gotta wonder.....

It is a little of negative placebo effect - if you really believe that class D cannot sound good it will not.

I suspect some truth there as well. I went in not totally sure but willing to believe anything. I think.

SMPS in mapman's amp can deliver 36 amperes for a full second!

And....loving it!

atmasphere, I’ve pretty much heard it all , including Atmasphere amps.

phase shift is just one factor that might acount for an expansive soundstage. You can’t equate the two or infer a large soundstage necessarily means phase shift being heard. if its truly phase shift that is there and not being mentioned then the reviewers need to go back to school perhaps.

For example, my setup has expansive soundstage only on recordings made a certain way conducive to that. on others it is quite the opposite. So there is no evidence there of artificial effects of phase distortion that would persist constantly. Certainly nothing that I can hear with any of my speakers large or small. You might measure something but I doubt anyone could single it out listening.

Maybe young pups with 20-20khz hearing and speakers with awesome bandwidth, but frankly there is a good chance that other forms of noise and distortion are what’s mostly occurring at the highest frequencies for various reasons, phase shift being one of many nasty things that occur there predominantly. Very little music does. Mostly just "air" at 20khz.. See the reference here:

http://www.independentrecording.net/irn/resources/freqchart/main_display.ht

So based on a combo of facts and experience I still see it as one of theoretical things that exist but do not add up to much if anything in practice for most.

Are you going to be producing an amplifier anytime soon?

Nope. Not my lot. I’m just a critical listener reporting what I hear and trying to understand why.

I already have two generations of Bel canto Class D amps. I have yet to hear any hint of brightness ever with the newer one. Even with Dynaudio Contour monitors known to lean that way with the wrong amp. It is an all in one integrated the C5i so less to get wrong or right when matching . In fact one of the reasons I bought it was to be able to compare and contrast with what I had. And guess what, better bandwidth and improvements in general with a newer and still evolving technology is exactly the thing that leads me to keep testing the waters.

As I said I do not doubt the relevance of bandwidth in theory, only is it an issue of enough magnitude in practice that most people would care these days when things are done well otherwise.

Some people report brightness in some Class D amps. Same true with other SS amps. Probably even with tube amps to a lesser degree. But I am not hearing it at all ever, in fact less than ever, with my latest and greatest Class D amp. So I do not find the fears bandied about with the technology in general to be warranted at all in practice.

Nor am I saying all Class D amps perform equally well either. Only the ones I own and know well for sure. That just proves to me it can be done now and today. I am not alone there I would say. YM always varies.

Its nice to hear a maker of tube amps and another of passive pre-amps gives the competing technology some credit. Its only fair to point out where the achilles heels lie. Every product has one. All good information for the educated consumer to mull over when making a decision.

Whatever Ralph meant the mid-fi comment did make me laugh knowing that the sound I hear from practical Class D amps today (like the ones I own which are neither the least or most expensive) is not mid-fi by any reasonable listening standard.

I suppose mid-fi is in the eye of the observer or the ear of the listener.

Nevertheless respected tube amp makers like Arc and Rogue have been on teh bandwagon for a number of years now knowing Class D is the ticket to get the sound their customers might like with most of the speakers out there today that are not overly  tube amp friendly. My local dealer sells Arc and Rogue (mostly tube amps for many years) and has jumped on teh Class D bandwagon even saying that the Rogue models he sells are the best sounding with the speakers popular with his customers (Magnepan and Sonus Faber).

The newer Class D integrateds I have heard like BC C5i and Rogue Pharoah and Sphinx are game changers for me. Prior to these, I would not have thought to ever replace separates with an integrated amp, but I would strongly consider that with any of these. The only downside is my Class D monoblocks are 500w/ch and all those go to good use in my larger system. In my smaller system, especially with more efficient speakers, the 60w/ch C5i comes very close to doing everything ever needed though a few more watts/ch would still likely only benefit.

60w/ch Class D and truly digital C5i has phono and line level inputs in addition to all the usual digital ins. Plus an outstanding headphone amp as well. Just add speakers and a digital source and you may be set with everything most would ever need sound wise.   In a single easily handled and manageable package smaller than the size of a shoe box.

I decided to try this (latest and greatest Class D and digital technology from Bel CAnto) prior to trying a tube integrated amp in this system and guess what its not going anywhere.

Mid fi has a negative connotation in these parts. That’s all. One can either laugh or be insulted. Best to not use the term unless that is the message intended.

Some amps of any type can be labeled as mid fi compared to others of same type, SS Class D, tube, whatever based on whatever criteria one chooses including the sound quality.

The point is not all of any type are created equal. Some of each type these days compete in the big leagues but play the game differently. Some in the minor leagues.

Also safe to say Class D competes well in all leagues at most any price point these days.

Its generalizing and labeling all products of a particular type equally for better or for worse that causes problems just like labeling all persons of a particular nationality or religion negatively causes similar confusion and problems, just of a lesser importance in the case of hifis.

The BelCanto C5i in particular has shocked me in that my quite tube amp friendly Triangle Titus speakers sound the best ever with it. The 60 w/ch are Ok but not the best with any of my OHM or Dynaudio speakers though I have had visitors from Agon still compliment the sound with those even. Which just goes to show it all depends. Class D amps play the game radically different than OTL tube amps do. But both can deliver big league results (Class D for less perhaps especially when cost of speakers factored in) based on my listening experience perhaps both even with easier load speakers that are required more for the OTL or tube amps but easier load in general tends to benefit all amps to some extent when done right.

Also I would note that modern OHM Walsh speakers (especially the larger models) are a good bit more efficient than Magnepans and not as tube amp unfriendly as one might anticipate. I found Magnepan to need power (though not so much current) to a much greater degree than OHM when I owned both.

Guido have you heard ref1000m amps respond similarly to power cords?  In what way specifically?  Thanks.

So much noise about nothing of real consequence.

I will of course look forward to improvements in switching frequency under the assumption that things will get even better overall down the road at least on paper. How much difference it makes practically is TBD.

George I do think you are too obsessed with this one technical issue. You should do a study to see if class d amp sound quality correlates strongly to switching frequency alone. To hell with all the rest that goes into these things if that is all the story.