A great article on Class D/switching amps

The latest edition of The Absolute Sound has, in my opinion, the best overall perspective and evaluation of the eight most regarded class D switching amps on the market today.

The article contains an explanation of the technology, an interview with a couple of the most important designers, the individual reviews and finally a round table discussion regarding these amps.

I believe any of you GON members who might be considering auditioning a class D switching amp would want to review this piece regarding their different sonic signatures.

I had the pleasure of listening to the Kharma MP150 which the panel picked as being on top of the "heap" compared to Audio Research 300.2,Channel Island Audio D-200, Nuforce Reference 9 Special Edition, Red Dragon Audio Leviathan Signature, Jeff Roland Design Group 201, Cary Audio Design A 306,and finally the Spectron Musician III.

Each amp had at least two different reviewers with different systems evaluate them and then compare their experiences. This was a well done piece and if you read it I believe you find it both educational and helpful to understand what these amps are all about.
I know this might come as a surprise but there doesn`t seem to be any shortage of technical articles & opinion on switching (digital) amps. Whether they`re ready for prime time is the salient issue for everyone to determine for themselves.
After reading this article and finding most of the reviewers critical of the treble/midrange performance of these amps, I take solace in the 1250 watt Class D plate amp in my Velodyne DD sub.
An even better article in stereophile regarding a $159 digital stereo amp with volume control--integrated in other words and listed now in their recommended components. You can't go wrong

Thanks, I'll cruise over to Borders and check it out !
Anymore cool threads, shoot-outs or reviews up your sleeve ?
Yes, these were very good articles in The Absolute Sound. Although the reviewers have probably forgotten more than I will ever know about audio reproduction I concur with much of what they said, but if not disagree I would offer a slightly different prospective.

I believe all the reviews were of stand alone amplifiers. I currently own a Jeff Rowland Concerto class D integrated amplifier which has essentially the same amp section as the Rowland 201 Reviewed. Two things are for certain with this class D integrated in my system. 1. There is a slight loss of air in the high frequencies (read that as ambiance) and 2. It is very sensitive to associated equipment especially cables. With that said I think one of the reasons I have been so taken with this amplifier is the fact that it is an integrated. Much of the component and cable matching have already been done by the manufacturer. Synergy is high with an integrated and I think that's a bigger deal with associated component sensitive class D amps. I would be interested to see what the TAS panel would have said if the amps were mated with that manufacturer's pre or if integrateds were used or if less demanding speaker loads were used (currently using JM Lab Mini Utopias with the Rowland which is a pretty easy load).

XLR interconnect cables from CD player to integrated have also made a huge difference in the sound. Much bigger difference than I have ever had with both tubed and solid state gear. Bad combination was using Kimber Silver Streak even though it sounded great in previous systems, too bright and brittle with the Rowland. Great match is the Synergistic Research Luminescence which has greatly improved the high frequency air and smoothness. Great too because that ended up being one of the cheaper cables I tried. In my experience much of what I hear with this $4,100 Rowland integrated (used price) is superior to amp/preamp combinations of similar combined value.

I don't think class D will be the dominate amplifier design of the high end in the near future but I do think class D will be one of three choices. It will no long be just tubes vs solid state but tubes vs solid state (A, AB) vs class D switching. Each offers their own strengths and weaknesses.
Ive listened to a couple digital amps and am not hearing half the neg. stuff mentioned in that article.Seemed like a strange article anyway.
I'm a subscriber of The Absolute Sound, but I didn't receive any issue containing the article you've mentioned.

I dropped my subscription to TAS a while back. Can anyone offer what specific issue this article is in? Sean
hey sean you can down load tas, i agree with chris martens view on the subject, mike
Sean, it's the November 2006 Issue 166.

Good, bad, or crooked, I love the audio press. If nothing else I've been turned onto many artist, via their record reviews, that I would of most certainly overlooked. For the most part they due their job of informing us to the best of their abilities and I mean that in the positive sense. The ability to give a product a negative review yet leave you feeling that the product may still hold promise in your system and side stepping the truly bogus products is as it should be.

TAS has awarded one of these class D amplifiers their Amplifier Of 2005. Then in this roundup/shootout they inform us that all but one has issues and that one was not the amp of 2005.

The true beauty of this class D article shows the reader exactly how ludicrous it is for the reader to get a clear picture of a products performance when no two writers are using the same equipment, regardless of their personal tastes? I believe most of these writers are very well experienced to preform this task, but when they rely on their sonic memory or refer to their notes of a past review it becomes obvious that the method is extremely flawed. Blah, blah, blah.

Class D has been around for some time but it's only been in the past few years that these designs have made stunning progress. I find class D to be one of the most exciting technologies in fidelity today. The investment is small, listen for yourself.
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That helped to pin down some of my feelings about the article,it was all over the place,like you said above if there ever was a time to listen for oneself this is it.
It is the cover story on Issue #166, dated November 2006. You can also download it (for a $10 fee) at
The overall tone was more negative toward these amps than I expected, but that
owes mainly to the comments of WG and JV. JV inhabits an audio ivory tower
and I think his perspective on these modestly priced products may be a bit
compromised. As for WG, I don't know, I've never been able to fathom his
perspective. The Kharma is his reference amp, but he dislikes the rest of them
and was outright brutal about the Nuforce. I got the impression Robert Harley
was scrambling to keep things from going too negative given that Class D is a
pretty big movement (understatement) in the market they cover.

That said, I do commend them for the comprehensiveness of the article.

Which Class D technology is the Kharma based on?
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I've alternated between Class D and low powered tube amps for about 3 years now and I intervened with a Pass Aleph 30. The Rowland 201 was very good but the amp I use currently is the best that I have ever heard. It is the Red Wine Audio Signature 30. It puts forth 30 watts per channel of Tripath power and operates off battery power. You get no noise and a very stiff current. Somehow, the designer, Vinnie Rossi manages to make this amplifier mimic the sound and character of a very good single ended triode. And somehow it missed out on the TAS article. I don't read TAS so I wouldn't know if he advertises with them. Does he?
The Red Wine Signature 30 is an intriguing amp for use with high efficiency loudspeakers.
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.
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.
The article was a start at best
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.
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.
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.
What is everyones cup of tea,thats boring.Seriously what do you think the Krell guy is going to say?
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...
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.

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.
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.
The battery powered Class T (I think...), Red Wine Audio Signature 70 monoblocks or Signature 30 stereo amp (recently reviewed on 6Moons) is intriguing to me. I believe they will be at RMAF in the Zu Audio room (Room 589).

I have not yet heard any Class D amps (NuForce, CI Audio, Red Dragon) that have persuaded me to sell my tube amp.
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.
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
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.
"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.
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.
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.
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.
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.
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 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.
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.

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'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.
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.
Duomike, is the Millenium the first Tact amp?
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, 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.
Class A or Class B.
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 D is high fidelity, but what I've heard in my system doesn't sound like real music yet.
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.