Class D Technology

I have a 40w/ch $85 Fosi Class D integrated amp with Bluetooth in use that sounds really good driving a vintage pair of Boston A40s. Audiophile worthy even, as long as you don’t ask too much of it. Cleaner/Better sounding than most comparable powered vintage receivers for sure. A better power supply would make it even better but add some cost. The TI chip used supports delivering even more power if wired up properly for that. It’s about the size of a pack of cigarettes to boot. So not a lot of bling, but otherwise....

That will be interesting. 

Hadn’t thought of DSonic in a while but looks like they are still offering a lot of bang for the buck.

Nice website.....lots of useful specs and measurements.

What Class D modules do they use these days?

erik can’t say for sure based on one or two example demos. These were about 3 years ago with newer larger SS Mc amps.

Personally I often would like to be able to hear an edge that’s not muted if in teh recording. Not in everything played categorically though. The Mcs would probably have been fine for this if set up the way I liked rather than how the dealer decided to do it.


Guaranteed the edge would be less on my OHM speakers versus with Totem or Dynaudio or many others that are not inherently more laid back in presentation. Only some modern pop .mp3 files I play from time to time have any edge at all with the OHMs. Much more so with Dynaudios in my smaller room with speakers not far from listening poisition and off same Class D amp. Most .mp3s which are inherently known for artifacts that can contribute to harshness/brightness are still quite listenable.


I’m a purest but not a pure purist.

I think were already seeing digital/Class D integrated amps make significant headway. The technology is so good already (low noise floor and distortion compared to separates) that I see no need for a separate pre-amp these days anymore quite frankly. When time comes to replace my current pre-amp I will likely just go with a Class D integrated of some sort based on my experience to-date with digital Class D integrated in my second system.

Well nothing’s perfect but in all honesty gotta say that Class D done well comes about as close in all ways that matter  as anything I’ve experienced in home/high end audio. Even without breaking the bank in some cases. If I were competing with it these days rather than benefiting I would definitely consider it a threat to my existence and take actions accordingly.

I've observed part of the maturing  of Class D technology in recent years is that noise as Atmasphere mentions is a valid concern that may have been a more common issue earlier on in some cases when not handled properly but should not be and is not in practice an issue normally anymore with newer well designed and properly functioning Class D amps.

My advice for anyone on the fence is do your homework, listen and decide for yourself.   Only then will you know.

Ah I see now glofi .    Let us know when you get it right.  

I've heard the Benchmark amp and was very impressed. 

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. 

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

erik last McIntosh demo I had was with Totem Mani 2 and other newer Totems. It was somewhat bright and glaring compared to other Totem demos I had heard. Other than that the Mani 2s left an impression and remain on my list of speakers I would like to own, especially with the right amp to make them shine.

I’ve also heard Goldenear Aeon monitors with folded ribbon tweets off NAD amps and there was no edge or glare at all there. In fact fatigue factor was extremely low, towards the polite side. I liked the Aeons a lot as well.

Its usually all in how well matched things are to work together in a manner that performs well and also suits the listener’s preferences (two different but related things).

BTW I have used Triangle Titus monitors now for many years with a lot of gear and these are currently running of Bel Canto C5i Class D integrated and the sound with these tiny very resolving monitors is the best ever. Absolutely no signs of brightness or edge which I have found to be possible with many amps.  The sound is just lovely overall. Same true with Dynaudio Contour 1.3mkII monitors I’ve used with the C5i. Both Dynaudio and Triangle sound absolutely marvelous with c5i (as do OHM Walsh speakers) but I lean towards the Triangles over the Dynaudios with the c5i mainly because they are more efficient than the Dynaudios and the 60 w/ch output of the c5i is plenty for the Triangles whereas the less efficient Dynaudios are not fully engaged with only 60w/ch.

Geekboy I run arc sp16 tube preamp and mhdt Constantine DAC into my Bel Canto ref1000m amps. Also a Bel Canto c5i integrated in my second smaller system. . I spend many hours just listening and enjoying more so than ever. Class D amps and my Ohm Walsh style speakers together are the most likely to not be replaced anytime soon at this point.

I used to covet the Micro Seiki tables but they were out of my price range back then. I settled for a very nice affordable and snazzy Philips 312.

My system I bought while there (dorm room sized) was Hitachi 802 Class G receiver, Phillps 312 table, Grado cart, Aiwa AD6550 cassette deck ( I loved that sexy beast), and OHM L speakers. Still have the OHM Ls that I’ve maintained and upgraded myself since. They can still compete and sound better than ever with my Class D amps.

I upgraded to a Tandberg tr2080 receiver I also coveted while at tech a couple years later bought at Leonard Radio on Route 17 in paramus NJ, a wonderful local shop  at the time.

Hifi sound is best when low distortion, effortless and dynamic. I experienced this as hoped in my larger room with larger speakers in particular when moved to 500w/ch Class D amps, but power and current hungry smaller monitors (more limited output in comparison) benefited similarly as well.

When I sold hifi back in 1978 (Tech Hifi), we had amps from 15 to 120w/ch available for comparison from many of the top lines of the day in a decent sized showroom.

Guess what? With any kind of decent speaker, the 120 w/ch model in a line always sounded best. Assuming realistic levels and dynamics matter. If not, or room is small, then not such a big deal.

Check this out:

http://www.enjoythemusic.com/magazine/equipment/0216/D_Sonic_M3_3000S_Dual_Mono_Amplifier_Review.htm

Them’s a lot of notes in the sound ratings at the bottom of the article!

Why would anyone with a need for monster power to drive their speakers best not consider something like this? The potential upside is huge for many.

Disclaimer: I am not that familiar with Dsonic, just citing this article as reference. Do not know return policy, customer service quality, etc., all things that matter.

The useful purpose of a custom input stage on most Icepower amps is to raise the input impedance  (10K to start with on older versions at least) to enable good performance with higher output impedance tube pre-amplifiers. Its a performance/integration enhancement not just there for "coloration". If pre-amp is lower output impedance SS there is no benefit at least on paper.

Benefits of improved power supply in any amplifier should be obvious.

I think Grannyring is right. Even the fairly modest Bel Canto c5i digital integrated amp is evidence of the excellence that can be achieved with newer digital technologies integrated and done well and that it need not cost a fortune. It is a true revelation of the magnitude say of HDTV compared to what was prior. Totally disruptive of what came before and not just another minor tweak or minor improvement on older technologies.

Here is another argument for Class D. It can be argued that once you get the bass right the rest is not so hard to sort out. I have found a lot of truth to that in recent years. Efficient Class D amps are both on paper and in practice hands down best at handling bass. That seems to be common knowledge based on application and sure enough I have found it to be true in practice. In a nutshell that’s mainly because of Class D high efficiency and the fact that doing extended bass well is exponentially more work for an amp than doing higher frequencies and efficient amps do it best. Just like efficient speakers make it easier for an amp to do bass well. The end result when done right (ie sufficient efficiency or efficiencies in play to facilitate doing the needed work) tends to sound similarly good in the end I find.

Erik I’m just trying to frame up the comparison between the various amp technologies in purely technical terms as an extension of georgelofis argument against Class D based purely on switching frequency.

I am of the mindset that understanding the technology helps to make decisions where needed but alone does not dictate what sounds best in the end. Technology alone cannot predict what sounds best in specific cases. A system together makes the sound not just one component. Its a team sport as they say. Plus individual preferences vary for many reasons though some technical people have a greater tendency to associate these with specific aspects of technology that matter to them whereas others (I’d like to think myself included) are not so fast to jump to conclusions.

So I think we are on the same page in practice.

Guess what? My Class D amps were preceded by two different Class A amps that were fine on their own terms but far from perfect in my application. The Class A amps were preceeded by many a Class A/B amp and even a 70’s vintage Class G that was nice overall in its day especially if space is limited but sound quality could not hold a bone compared to any good quality newer amp I compared it to.

I heard the Benchmark amp at Capital Audiofest last summer (along with every other kind of amp imaginable) and thought it to be a top performer easily in the same league with the best I heard there.  I would own it in a heartbeat.   I am strongly considering giving Benchmark preamp/DAC units I heard there a try which if if successful (as I expect it would be)  would finally happily eliminate the last tubed  gear in my house.  I'm all about the sound.   The technology used is just a means to the end.

Erik it seems reasonable to me to say Class A/B is technically inherently inferior to Class A for the reasons you cited. IS not good Class A always preferred over Class A/B for sound for the technical reasons you cited? Class A/B is used to keep cost power demands and size and weight down for the masses mainly (sound familiar?), not for better sound or performance. Whereas Class D is totally different and can actually challenge Class A especially as the technology continues to improve even further. Of course I prefer my Class D amps over any Class A/B amp I’ve tried already and even a lesser Class A I once owned.

The most unique value of Class D is when much power and current is needed (mainly for bass) as in case of many smaller more extended less efficient speakers that many prefer. As speakers get bigger, loads easier, and efficiency higher, then most any good quality amp can perform well without being too large, heavy and expensive for most, although each will still probably sound different and individual considerations including personal preferences come into play.

So practically, it really pays to decide what one wants or needs the physical profile of their gear to be to meet their needs then choose speakers and amps together accordingly to meet those needs. This practically is the most important thing to consider together I would say way more than any particular technical achiilles heel of any specific amp technology one might obsess on.

No amp including most Class A amps I would say are perfect so choose your poison.

In general., I find Class D amps are the best of all at taking total complete control of speaker which I find tends to yield the best results possible. The result is greater articulation and detail in the bass and a cleaner more dimensional sound overall. Cleaning up/controlling teh bass prevents masking detail at higher frequencies often buried by poor quality or muddy bass when amp is not up to the task of totally controlling the speakers, especially at the low end which is the most demanding and requires an amp to work hardest. Class D amps are MOST efficient and that helps enable achieve this more often than not compared to the competition I would say.

Bass reproduction requires the most work by far and is the biggest challenge for most amps. Class D does this best. For higher frequencies, other amps perform well as do the better Class D amps around these days so not as much to differentiate the technology there although skeptics will attack class D high end as its relative weakness which is a fair statement at least historically. But that "weakness" is one that seems to not matter at all practically as best I can tell these days. Even my modest newer BelCanto C5i integrated that I picked up for a mere $1000 used seems to have gotten everything just about as right as possible and that is a complete integrated amp with phono and DAC 60 watt amp and headphone amp. Its easily as good sounding as anything I have heard within its modest 60w/ch power limitation which will come into play in some cases. OF course no single sound will appease everyone so YM will always vary.

Can someone tell me what can be observed when measuring a class a/b amp that indicates its inferiority to pure class A?

I am off the opinion that Class A is the bomb when possible. However  class A amps to power less efficient speakers are large heavy expensive and power hungry.   So enter Class D as a practical option to inherently inferior (to class a amps) class ab amps. 

I do not have "ice modules" . i have stated repeatedly I have BelCanto Ref1000m amps. These use ice modules but also custom input and power circuitry and the price and sound reflects that accordingly.

Again generalizing and glazing over facts and details to help an argument helps nobody and is a disservice.

I would likely not have been satisfied using that older revision of vanilla Ice modules to drive my speakers which is why I opted for a better design. The original Bel Canto ref1000 was vanilla icepower (and much cheaper) and the differences between the two are well documented.


I don’t know what KEF uses or why. Its their choice so better to ask them. Probably just easier or cheaper or better for them to biamp in general which opens up options to use different amps for different purposes rather than try to get either one to do it all best at their price point. I’ve heard those those KEFs in my home and they are small power and current hungry speakers.   I'd definitely use Class D for teh bass with them but if biamped then many decent options for the less demanding  (power and current-wise) high end.

Don’t listen to the negative propaganda especially from just one or two who repeat the same thing over and over. Just try them for yourselves if interested and see.

Myself, I’ve had way less trouble finding top notch sounding Class D amps than others. Will probably never go back to anything else. If I had unlimited budget and/or went only with very easy load speakers, perhaps it might be easier to find other amps to match overall performance and sound quality I have experienced with Class D. But even so I have no reason to ever go back to anything else. My Class D amps do it all as well or better than anything else I have heard in recent years. If I were to seek a particular unique flavor of sound only available with a tube amp, maybe.

A good Class D amp is like a high performance car engine. it makes the entire experience a lot more effortless and enjoyable. Those who discount or ignore the advantages inherent in newer more efficient and overall higher performance Class D technology are doing others a disservice. I know I’m glad I went with my gut which told me to actually see what this popular and innovative newer technology is actually capable of before resorting to older more familiar solutions that never seemed able to fit the bill for me 100%.

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.