A great article on Class D/switching amps

Teajay, you got me, Reading back on what you say, I don't know what I was replying to. BTW Henry's amps are just a bit less expensive than the Kharma.

There is one big drawback for all highly resolving amps. A persons attending fair is likely to betray itself as not up to snuff. My Pass preamp was the first to go, then the wires, and after that I revamped my front end. Visitors have brought over their CDPs, and they all were non-listenable. I am now a super believer in non oversampling rigs. I did not spend a lot of money fixing things. Henry took care of the preamp issue. I did not have to look elsewhere.

For a lot of audiophiles, changing out stuff may seem normal. I am a conservative audio enthusiast.

As far as for sale items go,did we forget this a Agon,everything stereo is for sale sooner or later.

Its harder to build something with a limited budget and get good results then unlimited.There is just as many designers who cant build on a 30,000 ,as there is on 3,000 design,money doesnt matter,i dont have any Nuforce never heard it,but look at all the people voting with their money on that one,to say something like they cant hear or this isnt right compared to other products is simple wrong,ice or whatever platform can free up the designer to do his magic,like somebody above said good job B and O,Ucd,good job and well done to each and every platform.

Branimir, you are quite correct. I have never auditioned the present Krell Evolution generation of amps. I was refering to past experiences with prior generations of Krell gear, that was not my cup of sonic tea.

Muralman1, it sure would be fun to have Nelson come to your house and see what his opinion of the H2O amps would be! I just don't understand your statement, " Who says there must be one design", I did not say that or even imply that there is only one design or type of amp that is surperior sonicly to all others. I also firmly believe that D/switching amps will get better and better as more talented designers get involved with this type of amp design.

Teajay, there have been two pairs of H2O amps for sale recently. One was sold along with speakers for financial reasons. The other sale was speaker driven IMHO. In any event, that seller is a die hard tube lover. There is no telling for preferences.

I would love Nelson to drive down the hill to hear what I have. My bet is he would change his design priorities straight away.

Who says there must be one design? Henry makes ICE ASP amps at a substantially lower price for those who want them. He sells the Signature monos direct, and makes only a decent return. It takes some dough to make these amps in America.

Copy that, Coffeey. Why should a pair of speakers or an amplifier or a turntable cost as much to produce as a luxury car? Or twice as much? The prices of modern high end equipment are downright scandalous. We audiophiles seem to be goose stepping along in mass hypnosis nodding our heads in agreement about what a bargain a $600 power cord represents.
I think the reason behind the endless proliferation of new high end manufacturers relative to the nearly static growth in the number of audio buyers can be explained by the preposterous margins enjoyed when a sale is occassionally made. I never really fed this beast in any big way in the past but I'm going to try to starve it from now on by seeking products which do very well for little money. Class D seems to provide that option.

Also I think part of it might be ,do you really need 40,000 to build a reference,seriously 30,40, 50,000 thousand,pretty ridiculous when it gets right down to actually.

And in doing such a comparison as the Ab. Sound did,most of the amps probably did ok to very good compared to how they set everything up.There is no haze or colorization to what i listen to.

I think the latest issue of TAS has a good summary of prevalent opinions on class D amps and why they differ.

Thus far I have heard some class D amps that I find sound good and some that I don't. I have had no opportunity to compare these with other linear amps. I owned some class D amps in the past and not been very impressed. The ICE modules, however, seem to be a substantial improvement.

Down here where I live, the question of whether or not a Class D design is superior to $40,000 Class A amps is utterly academic. My RWA Signature 30 is the best sounding amplifier I can afford and it outperforms anything I'm aware of at less than 3 times its price.
The mere fact that we are discussing subtle areas of comparison between the newcomer, dirt cheap digital amps and the finest, most expensive conventional designs speaks very well of the future of Class D.
In photography, we might find a parallel. I'm told by some hobbyists that film provides a certain character that digital doesn't quite convey but that digital has a clarity and precision that film was never able to capture.

Teajay,
Usually I agree with you, but not this time...
You apparently did not audition any new Krell amp(Evolution One, Evolution 402, 600 or 900) because they simply do not have anything similar to Halcro's(DM88,DM78 or DM38). If fact if Halcro is flavor #1 then new Krell's are definitely #2! New Krell amps use zero global feedback with just 8db of local nested feedback. Of course I am biased since I own one of them, but your description is section 1) is IMHO not accurate. Even A.H.Cordesman liked them in his review(BTW, he is known Pass fan!)...

Now back to original subject, class D are still not at the best level IMHO. I audition only two of them in my home(Jeff Rowland Model 501 and Audio Research 150.2) and both were nearly not as good as current SOTA tube or solid state amps IMO. Jeff Rowland Model 501/Concerto Pre combo were better then ARC 150.2 is every way, but they could not stand against my reference amps in any way. As I said before bass was very good and tight in Model 501. Midrange is pretty good, but somehow artificial to my ears and highs... High Frequency needs little bit more in-depth description, low highs are very open and almost bright sounding, but upper highs are closed-in or non existant! Exactely as J.Valin described in his review, they are cut off. Soundstage size is just decent and depth is a big problem in both Model 501 and specially in 150.2, depth impression is pretty limited with both of them to my ears.
To be absolutely fair I must say that Model 501 needs to be compared to tube or solid state amps up to $10k IMO. So, my comparison is not very valid to most people...
Also, when you buy Pass, Krell, Boulder, ARC, CJ, CAT, Lamm etc. you get the design and long time work of N.Pass, Dan D'Agostino, Jeff Nelson, Ken Stevens, Bill Conrad/Lew Johnson, Vladimir Lamm etc. In class D amps you get B&0, Tripath etc. modules implemented by some "desingers" in different metal(or not) boxes. These days great name like Jeff Rowland is simply putting somebody else designes in his excellent metal boxes. Also 99% of class D amps use switch power suplly. Good or not? Only time will tell...
Limited bandwith(mostly 5hz-60khz)... Since class D natur is limited bandwith, is it also a limiting factor soundwise in class D amps? Big damping factor(usually above 500)... It also impact pretty much on class D amps sound IMO.
Do all class D amps sound the same? Based on my limited experience(only two models) I think not, but they all share some things(strange timbar IMHO and soundstage depth shortage).
"I believe that many of the class D amps are very good bargains for their price range, but do not yet compete with the reference class a/b amps quite yet in their development. I'm quite aware that at this level of gear we are really talking about personnal taste and system synergy, so there is no "right" or "wrong" answer to what are the best amps or designs in the world."
Here Teajay I full agree with you!

Chris, you asked a great question, so let me answer it in three ways:

1) As a reference point I'm not a fan of amps like Krell or Halcro or speakers like Wilson because I find them to have certain qualities (details, dynamics, transparency) but for me I found them "sterile/cold" sounding which I do believe has much to do with their way of presenting timbres and harmonics in their overall sonic presentation.

2) Another example would be the Pass Labs X series, that I found quite dynamic, detailed, with great extension, but not very "musical" to my ears. However, when Nelson Pass came out with the XA and X.5 series, it kept the dynamics but also returned the timbres/harmonics of his Aleph design.

3) So, when I have listened to a few of the switching/D amps they offer great clarity, dynamics, and a silky presentation, but not the realistic timbres I hear in the best of class A linear amps.

I believe that many of the class D amps are very good bargains for their price range, but do not yet compete with the reference class a/b amps quite yet in their development. I'm quite aware that at this level of gear we are really talking about personnal taste and system synergy, so there is no "right" or "wrong" answer to what are the best amps or designs in the world.

Right on, Dazzdax

Teajay, Henry has class A amps that will give your XA-100 amps tough competition. He isn't producing them because class A is a far cry from what his class D amps sound like. His first ICE amps were very much like the best of Class A amps. Now he has moved on towards making them sound just real.

Like many threads, this one has evolved, one idea building on another. There is no doubt simple class D amps are not the equivalent to first rate class A amps in some respects. What was brought out was a linear power supply steps up both the sound and the cost of a class D amp.

TJ, what is in your opinion the biggest flaws regarding the sound of class-D amps? Lack of harmonic structure? Do they sound too "artificial"? And why? In my opinion the sound of class-D amps (and in my case, the ICEpower based Acoustic Reality Figaro's) is very clean and smooth, very "neutral" and accurate with awesome bass. I hear none of the typical signatures of solid state (some kind of "haze" and coloration).
PS: I'm only trying to find out what distracts people in case of class-D amplification.

Chris

Vince, without being disrespectful or mean spirited towards you or Mr. Ho, if he can make his D amps sound exactly like my Pass Labs XA-100's or a dartZel I will order a pair right now.

This sounds like a claim made almost twenty years ago by Bob Carver, that he could build an inexpensive amp to sound like any amp in the world, regardless of price. Notice, no one considers his amps "classics" in any way today.

When I started this thread I did mention that I had listened to the Kharma D amp and thought it was quite good, but the pair does cost around $6000.00. So many of these D amps offer alot of performance for the money, but the reality is sometimes you do get what you pay for, which means that these amps sonicly are not at a reference level yet compared with linear a/b reference amps.

Hi Vince (Muralman) and other fellow Audiogoners, there is still this dichotomy between the class-D followers and class-D opponents. Personally, I don't get it. Some people say class-D is in it's infancy (that's true), class-D is bad because..., bla, bla. But when one listens, class-D is not bad at all. It is quite good. I think it is even very good (sonically)! We are audiophiles. Most of us know a lot of gear. We regard live sound as absolute reference. But why do our hearings differ so much with regard to class-D amplification? Do you have an explanation Vince?

Class A or Class B.

Arthur, I applaud you for getting your PhD. I am puzzled by your proclamation. Just what genre of amp do you prefer over class D? I have listened to all tube gear, and delved into it myself. I have heard a great deal of solid state amps, and have owned some of the finest. There is no doubt in my mind, nor my listener's minds that class D has got to be the cat's meow. The designer of my amps, Henry Ho, has told me he can make the ICE module sound anyway he wants. He is a senior electronics engineer, with a passion for audio.

I am doing my PhD on Class D amplifiers but I won't own one for my stereo. There is still a ways to go in the design of switching output circuits. Crown is one of our sponsors and they are really pushing research in this area so it will come eventually. Having said that, switching power supplies feeding linear output circuits is a great idea more manufacturers should look into IMO.

Arthur

Duomike, is the Millenium the first Tact amp?

Muralman1, you are right as rain, excellent point. I myself have determined that an oversized power supply has provided more depth on some gear I have owned.

I'm using a Tact Millenium class d amp since '99 replacing at that time pass aleph 2 mono blocks. The tact is different to the newer designs. I directly converts PCM to PWM so no DAC needed. Volume is adjusted by adjusting the voltage which is been switched.
in 2001 I had high a friend with a very high end system: 12K transport (TL0) going into AN DAC 5 limited edition, preamp was Conrad Johnsson Art and amps with AN single ended Keigon mono blocks driving Wilson MAXX speaker. Once took my Millenium over to my friends place replaced all that very expensive tube gear (pre/power and DAC). To my and myfriends very surprise that tact sounded extremely similar to the tube stuff!
Got the amp modded recently and extremely happy with dring my Omega DUOs.
Michael

The lack of depth is a power supply problem. The digital power supplies can be steely accurate, but it takes a big analog power supply to bring out the best from the ICE amps. I enjoy tremendous staging side to side and fore to aft.

I have consistent findings regarding the sound of my eAR Figaro's at home (modified ICEpower ASP1000 modules). These findings comprise: more lifelike sound than previous conventional amps I owned in the past (Mark Levinson 333, Jeff Rowland Model I, Accuphase A-50V), better and deeper bass, more pristine treble. Better midrange dynamics. The only thing that is probably less than the best conventional amps is front to back depth (ICEpower sounds somewhat flatter). At first listen there can be some impression of too little midrange fullness or density, but this is probably due to less distortion and coloration. Some have to get used to it. Briefly I can say that listening to the eAR Figaro's it's as if some "live" mic feed is being passed through the speakers. With conventional amps (solid state or tube) the music is emanating from the speaker itself.

Chris

Phd and Tbg, B&O recently spent a great deal of man hours improving their least popular module, the 500A. This module requires an add on power supply. The designer of the H2O, Henry Ho, cut his teeth making class A amps for his own use, and later for sale. His class D amps benefit from Henry's deep knowledge of conventional amps. B&O knows their best sound is sourced from outside designers. It is a matter of prestige they provide a great quality module to them. I have their new module inserted into my analog power supply H2O amps, and I want to say thank you B&O.

Tbg, keep in mind my above statement is strictly a matter of opinion but you probably already know that there are currently some digital amps that employ an analog power supply and some prefer it. It is unbelievable how much marketing hype there is behind some digital amps. At first, after reading some of it, this left me feeling that my analog amp was outdated technology. As some audiophiles unload their analog amps there will be many waiting in the wings to grab them up.

Phd, with the B&O ICE module readily available, I don't think you will see an analog power supply. In fact at the rate they seem to be selling, I expect little further developement for the next year.

Most of the music hangs out in the midrange and is a critical area where digital amplification doesn't seem to address as well as analog. Besides that they (Class D) fail to provide the texture & harmonics that makes music an enjoyable experience. Yes they get alot right and may be our future but they are currently work in progress as some have agreed. If I were to settle on a Class D amp it would have to have an analog power supply.

The Red Wine will not drive a difficult load. It goes head to head with SET amps, and fairs exceedingly well. Krell's real threat are the powerful Class D amps like my H2O. It thunders as Krell amps only try to, while being airy at the same time, Krell only wishes for.

Krell Dan has good reason to dis Class D. In fact, now that you bring it up, I can see that the entire TAS family is threatened by a superior product at a realistic price.
The Red Wine Audio Signature 30 is far more musical than any Krell amplifier at any price regardless of what Dan has to say on the subject.
Any comment issued by Krell against a competing product or technology should be considered tainted by self-interest. Clearly he has a great deal at stake when his megabuck monoliths stand to be obsoleted by something easily affordable and more musically adroit.

"Class D will seem cold and sterile because it lacks the distortion components that they interpret as warmth."
In the designer's forum, Dan D'Agostino from Krell objected to class D because the waveform produced was furry and spiked. Class D has a lot of distortion that needs to be filtered out. And as with any filter some bad stuff may get through and other stuff not pass through. The best application is a subwoofer amp.

I had a JBL IceCube class D amp in 1976. It had a switching power supply as I recall. It ran the hell out of my Infinity Quantum Line Sources. I think the present rage would not have happened except that B&O developed their little cubes which everybody or nearly everybody buys for $150 each and which B&O does not want to sell as a completed amplifier.

Didnt "class D Start out in proffessional audio amps designed to save space. I wondered how long it would take to trickel down to home audio. ( Not Fo me ). Bass is the strong point

Tvad - I'm speculating here but I always assumed that Class D indicated "Digital", and Class T was just a made up designation for Tri-Path which Vinnie uses in his Red Wine amps.
Tbg - You raise an interesting and valid point. Categorical dismissal of all Class D products is a bit shortsighted. Certainly they will vary in sound just as we vary in taste.
There is something for everyone and all any of us needs to do is find our own favorite. There is no Absolute Sound. That's Absolute Foolishness.

This topic raises blood pressure. Isn't it curious? I find the entire idea that there are two classes of amps with all within a class sounding alike unbelievable. Even among class D amps I hear great differences, and among class A/B amps, I have had probably 20 different one and heard great differences.

But what is most interesting is that we argue in print about what we hear. Who cares what others think? I know that I am anxious to hear the Red Dragons and have no interest in the Rolands or Nuforce amps.

Dazz I think you're being too simplistic about this. I like some class D amps, don't own one, but wouldn't place myself in either one of your divisions.

However, the topic seems to rise blood pressure in many audiophiles.

There seems to be two parties, in which the audiophiles could be divided: audiophiles in one party dislike class D amplification because of the artificial, cold and non-organic sound, while the audiophiles in the other party like the class D amps for having a clean, dynamic and true to life sound. Why does this outspoken dichotomy exist? Why do some audiophiles prefer the sound of class D amplification in stead of multi thousand $$ conventional amplification? I read a story about this very rich audiophile who replaced his one million $$ worth of WAVAC amplification with class D amplification and it was not because he needed the money. It is quite puzzling to me.

Chris

Teajay, I had a chance to audition Jeff Rowland Model 501/Concerto pre combo in my systems and did not like it at all. Despite nice, powerfull bottom end everything else in sound presentation was wrong IMHO. As J.Valin correctly ponit out treble info is very limited and you got "cut-off" feeling most of the time. Midrange was detailed, but somehow mechanical in presentation. Two friends of mine visited me during several days(actually 25days!) auditioning period and both of them did not like Rowland sound. One of them owns same amps(Pass XA100) as you do. I also had a chance to audition Bel Canto REF1000s and did not like them as well.
BTW, it is pretty interesting that both J.Valin and R.Harley did not like D-class amp too much, but both of them are using pretty good tube and solid state amps as their reference's.
IMHO D(or T) class amps have a very long way to go before we will have something of truly reference calibar here. That strange high frequency behaviour is still a problem of most D class amps and this problem is not pretty simple to solve(look at the way D class amps work).
Of course, it is only my humble opinion...

What is everyones cup of tea,thats boring.Seriously what do you think the Krell guy is going to say?

Again I cannot imagine that Class D or ICE amps all sound alike. I have not had the opportunity to listen to them side-by-side, but only one, the Red Dragon, caused me to go back repeatedly to listen to it on the Audio Zen speakers.

Bobgates -
Let me respond to each of your comments separately.

I would agree that Class D technology is still evolving. Those things which are not still evolving have been abandoned.
To some reviewers, Class D will seem cold and sterile because it lacks the distortion components that they interpret as warmth.
As for the used market, please note that Class D is not so new. I bought my first pair of Rowland 201 about a year after they became available and that was 3 years ago. The fact that something is for sale on the used market doesn't "goes to show" anything other than the fact that people bought them new and decided to try something else. In fact, it might well mean that they liked Class D so much that they upgraded within the genre.

I read the article in the latest Absolute Sound and it would appear that the Class D technology is still evolving. Interesting that the reviewers either seemed to love them or hate them; one reviewer in particular seemed to characterize the class D amps as cold and sterile and didn't like the majority of the amps reviewed. For a new design there seem to be several of these class D amps on the used market already which goes to show that they are not everyone's cup of tea.

The article was a start at best

I got a chance to read the article and thought it was pretty well written. I wish I could have had the chance to hear all the amps in the article. I own a pair of Nuforce monos and like the price to performance. They do many things very well and for the money it is an easy choice to live with....until I go listen to my good friends VAC tube amp & Messenger preamp. The technology is interesting and hope it keeps evolving to bring exciting sound into more budgets. The gear that the class D amps are compared to in the TAS article is kind of ridiculous in my eyes. Why didn't they make more comparisons to some comparably priced solid state & tube amplifiers? I think what Robert Harley says about auditioning in your own system is spot on. I wish more manufacturers made this possible and somewhat practical without having to lose your shirt by buying new and selling used, or pay a 10 or 15% restocking fee.

I agree with Tvad about the Red Wine Audio Signature 30 amplifier that is battery powered being interesting. I am even more intrigued about Red Wine Audio's new Signature 70 monoblocks that are coming out next month. They are on my very short list.

That's right, Tvad. The Sig 30 provides a very convincing argument for switching to high efficiency speakers. I've seen numerous testimonials now saying it may be the best SS amp available. And at $1400 for a single input integrated, it has to be the best overall value on the amplifier market.
Consider Reference 3a or Zu Druid as good speaker choices.