Class-D amps - a different re view

Martin Colloms, the editor of HiFi Critic (ad-free mag from the UK) have recently published the review of several different Class-D amps, together with an in depth technical analysys and measurments.

His conclusions were not favourable, to say at least:

"I regret that not a single model merits unqualified recommendation. Price is not the issue; the poor listening tests speak for themselves. (...)
At present we have to take the prudent view that good sound might be possible from switching amps, but we haven't heard it yet."

BelCanto REF1000 (ICEpower) - score 10.5 pooints
"The ICE power module used has a dependable reputation, and the design is well built and finished as a whole. While I would not suggest that you shouldn't try this amp, on sound quality grounds alone I cannot recommend it for audiophile use."

Channel Islands D100 (UcD) - score 13 pooints
"While I have reservations about a number of aspects of sound quality, and advise personal audition, given the solid lab results (...) the overall performance and the moderate price, these CA Audio monos do make it to the 'worth considering' cathegory."

NuForce 8.5V2 (proprietary technology) - score 9 pooints
"Yes, the price is good for the power output. Yes it's pretty, light, small and runs cool. However, the sound quality simply does not justify recommendation." (on top of that the NuForce amp measured very poorly - Elb)

Pro-Ject Amp Box (Flying Mole) - score 5 points
"I'm sorry to say that Project (...) was a real disappointment in the listening tests, and can't be recommended."

Just as a point of reference, recently reviewed Krell 700CX scored 100 points, CJ Premier 350 - 110 points and ARC Ref 110 - 135 points.

At least someone have had the balls to say it. This is why HiFi Critic is THE mag to subscribe.
What kind of balls does he have? I like to play catch with my son, we use a football or a baseball...



Nrchy, I like your humor. ;-)
The Absolute Sound surveyed several Class-D amps in the November 2006 issue. A couple of reviewers liked the sound of a couple of amps, but most did not. A typical comment from memory, "great bass (that's why these amps are used in subwoofers) but the midrange treble are not so good."

I don't have the issue any longer and don't recall if every reviewer listened to every amp. The general consensus seemed to be, "interesting technology, not ready for prime time, no recommendation, but go have a listen for yourself." The overall tone was fairly negative.
I've had a lot of different gear. I like to try different things and make up my own mind based on my experiences with that gear.
I currently own a pair of modified Bel Canto Reference 1000 amps. These amps are the best sounding amps I've ever had including my Odyssey Stratos Extreme mono's.
Associated equipment is a big part of the sound I'm getting but that's how it is in every system regardless of the gear or the money spent.
While I put some value in the reviews, I realize it comes down to what works for me. Bottom line is, if you don't like it or it doesn't work for you...then don't use it. Variety is the spice of life and that's what keeps our hobby interesting and fun.
What floats one guy's boat might just sink anothers.
Want to talk about balls??? I've worked hard to put together a system that delivers in a satisfying way and believe system has great big balls headed up by the Bel Canto Reference 1000's.
My rig consists of:
Modified Bel Canto Reference 1000's
Bel Canto CD-2
Bel Canto DAC-3
PS Audio P1000 ac regenerator
Stealth Varidig Sextet balanced digital interconnect
Jena Labs Pathfinder XLR interconnects
Michael Wolff Bohica II power cords
Kimber PK-10 Palladian power cord
Jena Labs Valkrye Twin 15 speaker cables
Bybee Golden Goddess speaker bullets
Custom T6 MKIII speakers from Chapman Audio Systems

Class-D amps rock. That's my view!
Interesting. Elberoth2, Can you share anything about the Nuforce measurements?
I am now driving my Magnepan 20Rs with a Spectron Musician III and previously a pair of Bel Canto ref 1000 monoblocs and both bested the big boy SS Class A and A/B amps that I have had in my system before.
The Absolute Sound roundtable on class-D quite some time ago came to the same conclusion.
I also enjoy the magazine. Expensive but worth it.
I'm going to assume that you took a snippet of his conclusions. I'd be interested if there were any supporting impressions. However, I don't see any above. Did Mr. Colloms say why he came to these conclusions?

All I can say is I'm running a pair of Bel Canto Evo 200.2's in bridged configuration and I couldn't be happier. They have the power to make my Martin Logan's come to life, and they sound superb -- smooth, musical and well balanced across the frequency spectrum. In my case they beat out other very well regarded older amps from BAT and Classe. If you have more info, please share it.
One thing about him-he speaks his mind and doesn't care what anyone else says. That is the prerogative of someone his age. It reminds me of the old phrase, "not always right, but never in doubt". I really appreciate his views on loudspeakers,cables and A/B testing. He has been around long enough to have seen it all.
Elberoth2 audio reviewers are like any other profession. If you look hard enough you can find someone who will say what you want to hear. I am not here to say that class d is the best or worst. All i am saying is as far as nuforce goes a vast number of reviewers have found the amps to be some of the best they have listened to, so what. The only one who can make a statement of like or dislike is the buyer who compares the products themselves. And anyone who makes a purchase of any product with out trying it first is like a lamb being lead to slaughter. Or is some cases they just got lucky. JMO
If i can ask what were you getting at with this post.
A friend of mine who pops in here once and awhile who I respect for his knowledge, experience and equipment (he has a Walker table wich grants everyone else instant fame and respect in these forums) switched from his near 200lb Krell pure class A room heater to (2) 7.5lb D amps and likes the results, he still has the Krell only because it was a hassle to try to sell, though he tried.
I cant recall the model, I do think he said they gave 500w per channel and were less then $2000 per point is I dont beleive these amps deserve the thrashing the recieve atleast not without an educated length of personal experience and un-biased evaluation.
Oh great... another slam the Class-D amps thread. How original!

My view is that a lot of audiophiles just don't want to believe that class-D amps can compete with and oft-times outperform the best conventional ss and tube amps available.

This is the conclusion I've reached after hearing the NuForce 9SE V2 amps in my system. They sounded very good when I had them set up with all solid-state associated gear; but now that I'm using a custom 6SN7 tube preamp, I have to say that in my view this combination beats everything I've heard to this point...

My hunch is that the NuForce 9SE V2 provides such a transparent window that what I'm hearing is the unadulterated sonic signature of the 6SN7 linestage, which is a stunningly gorgeous musical signature. It provides the most wonderful midrange and highs I've ever heard; and of course the bass kicks butt too.

Believe what you will. Ultra Audio, HiFi+, 6 moons, Positive
Feedback, Audio Critic (reviewing the ICE powered B&O BeoLab 5), Stereophile, Absolute Sound, etc., etc., all seem have found positive things to say about the Switching Amplifier technology. I have a Tripath based amp and I refer you to the Red Wine Audio review in the latest issue of HiFi+. It describes the sound better than I ever could. I remember all the hoo-haa when CD first came out. This all seems familiar.
In the end I have to go with my own ears. I had graduated to Plinius 102 and tried the Nuforce and ditched the Plinius without a second's thought. The Nuforce was more real, and removed the stodginess and electronic hash of the Plinius.
if they keep making them, it means there is a market for these amps. I personally don't like the sound of Class D amps but know people who do. Some people don't like tubes, some don't like solid state. It doesn't make tubes better than SS or SS better than tubes.
It's personal prefference.....whatever works for you in your system.
Ladies and gentlemen of the jury, this is silly. Even a casual read about Class D amps will make it obvious it's all about system synergy. There are so many variables!

Maybe I just happened to get it right.

I'll bet if someone invented truly perfect sound reproduction it wouldn't sound perfect to some people who hear things in their own way.

As for measurements... don't we all know that better testing gear doesn't always sound better?
Class-D has tons of potential. I think the Gilmore Raptor's sound fantastic. I have also heard great things about the Spectron sig. He mentioned price was not an issue, but the more expensive Class-D amps do sound much better.
I recently heard one of the writer's favorite two conventional amps powering some Apogee Divas. I can't wait to get to the same place so I can wake up that tired sound with my class D amps.
I have Trend ta 10 and it is superb amplifier for very little $$$ when driving Klipsch LaScala horns and when it is battery powered...I have also Shindo amplifier, which is also very nice with the same speakers. The sound of each is different, but if you listen to music, each of these amplifiers can get you "involved" and it is for me the best, you can ever dream of from HI-FI!!!
Myrtle said it best. I'm sticking with my Bel Canto. If there's a weakness, I haven't noticed. Too busy listening to music.
Interesting that the reviewer rated only the UcD amp (CI D200) as worth considering. I agree with the ICE/UcD finding, but lack of an assessment of a Tripath amp is too bad. My Tripath CarverPro ZR1600s are right up there with my CI D200s. However, the rating gap between all the digital amps and the conventional amps is so absurd that it calls into question the validity of the entire review.
Addition to my above post:

Take a look at mjfvashon and Platos comments above. The Bel Cantos in mjfvashons rig and the NuForce in Platos both let their superb front ends ie Bel Canto DAC-3 and 6Sn7 based pre respectively shine through. I drive my Spectron Musician III with either a deHavilland Ultraverve octal based pre using 6SN7s with a 5AW4 rectifier or a highly modified 6922 based pre both with superb results. Maybe in our systems it is the synergy or resultant open window on our pre that makes our systems work so well. FYI I am using a BelCanto DAC-2 with various transports for source.
this isn't unlike the backlash that many companies took when tubed gear was displaced by ss designs...the more things change,the more they.....
As I said in my initial post - those are just his conclusions. The original review is 14 pages long - full of technical analysys, measurements and his impressions. The amps were very well run in (500h), he tried varoius power cords, varoius inputs, varoius cables, supports and associated equipment. It really is one of the most complete reviews I have read in a long time.

If anyone is interested how he came to those conclusions, I suggest you get the copy of the mag. Sorry, I cannot reprint more of his writing (I prolly already have broken some copyrights), especially that it comes from the current issue.

The mag is expensive (it has to be since it is ad-free), but it is worth every penny IMO.

BTW - I have nothing against Class-D. I have owned BelCanto eVo 4 mk II (Tripath based) and also evaluated for an extended period of time the ICEpower design in my system.

The original title for this post was "Class-D amps - a different (re)view" but somehow the brackets were removed by AudiogoN software. It changes the meaning a bit.
It seems like one of main points of this review is, that it was done by a reviewer who doesn't except any advertising.

Well is that same vane, I suggest another reviewer "10 Audio", who also doesn't appear to accept any advertising.

They found an ICE based switching amp to have performed quite good, beating out the majority of other designs in price to power ratio. Not to mention size, heat, weight and power consumption.
I wonder what Mr. Colloms will say about the Halcro next. I have a chance to audition the entry level Hacro Mc20/ Rogue 99 pre-amp/ Esoteric CDP with my LFT ET8b at the local hi-end dealer and I cannot believe what I am hearing. Ten years of loving for Martin Logan and Krell has been replaced by what I hear. I ended up with a pair of ET8b. The Halcro is next on the list.
Martin Colloms is absolutely right - he did extensive listening and extensive measurements. Note that with exception of Spectron no other class D manufacturer disclose its full specs - and it should tell a lot!!!!

Entire panel of TAS reviewers come to the same conclusions in Nov 2006 issue 166 of TAS

Its is obvious that all owners of class D amplifiers would reject his/their conclusion because to accept it is to acknowledge that they did "poor" choice.

None less, people who auditioned Kharma monoblocks ($29k/pr) are very happy with their performance.

Spectron Musician III (one of the amps reviewed in TAS issue 166) received, this month, TAS Editor Choice Award without a single caveat.

As far as I know, three rave reviews (one in TAS) are coming to describe its Signature Edition.

There are superb designers in this world who produce...superb products.

NuForce, when does not need to drive difficult load which it can't, doing admirable job too.

I heard that Jeff Rowland $14k class D amp is also excellent.

So, its not all lost... ;--)
Hey, no worries. I wonder what the mag would cost mailed to the US.
I was not a fan of class-D amps untill I heard the H20 Signature monoblocks. They changed my mind.
"NuForce, when does not need to drive difficult load which it can't, doing admirable job too."

My Nuforce's have zero problems driving my Aerial 10T's and they are certainly not what I would consider an "easy" load.
I agree that Class D amps have a lot of potential. We have only scratched the surface of this new technology. It may not be quite there sonically yet but it is getting closer, and according to some as stated above, it is as good or better than conventional amps. There is a lot to be gained in terms of size, efficiency, cost, etc. And don't forget that some amps with conventional output stages have been designed with switch-mode power supplies.
Woodburger and Bbro have said it. Synergy is where it is. I have found naked speaker cables make night and day differences. Same goes for non-oversampling. The preamp choice is paramount as well.

As class D amps continue their spread, we will see cable and preamp builders bringing out more great class D friendly gear.
I am late to this party,but want to give a simple opinion.
Firstly, virtually all new technology gets "knocked" when first introduced.Nobody wants to give up their present stuff.I don't think any owners of Class D designs should get nervous,from some criticism,especially if it sounds good to you.You cannot have too bad hearing,or you would not be in this hobby!!
Secondly,the Abs Sound forum is yesterday's news,as it took place a while ago,and technology has improved since then.I do remember Jeff Rowland stating he would use whatever "modular" technology he felt was advanced enough,and good sounding enough to put in his stuff.He seemed open minded about the newer technology,and wanted to embrace it,while it appeared(to me) that Dan D'agostino was intentionally contradicting Jeff's input.Look what has happened to Krell,these days....Just a thought.
I don't own a "D" class amp,but did have Jeff put in two of the industry's latest Switch Mode modules in the power supply "second" chassis of my "two" chassis 8T amp.I previously had an older S.M. module which replaced and outperformed the battery held within the second chassis.I didn't think it could,but it most certainly was quieter and far more dynamic.
I was extremely happy with the battery,but the new S.M. "original" update was considerably better,period.Believe it or not!!NOW the dual module S.M. power modules that have gone in recently, absolutely outclass both the battery,and first (superb sounding) S.M.(switch mode)power supply.Who knew?
I was sceptical at first but the performance is rediculously good!....The amp runs COOL too!!To me "that" is a "cool" thing....My previous Krell mono blocks,which sounded just fine(driving my Avalons)required a dress code.Which was to wear nothing but a Speedo,even in the dead of winter,due to the rediculous heat output.....Sometimes one actually likes to be comfortable when listening to music.
My tube amp days were fun,but I would always use my tennis sweatbands,during long listening sessions.I am serious.Not really!!-:)You know what I mean.
As to the actual class D all honesty,and of course only my opinion.....I have heard the Nuforce amps,and the Belcanto amps,as well.I was "extremeley" impressed with their sound quality.I,also,was sitting in comfort during the listening sessions.Of course I did not bring my son,the doctor's(had to slip that in-:)stethescope with me,to see if I could make out any wrong doings in the music.Whch sounded great,btw.
The future looks bright for these designs,and I could care less what a reviewer thinks.It is my own ears,and comfort that matter to me.
Best regards.
Fazio, check out what I did with my H2O monos and speaker cables. The cables cost a couple dollars apiece. Write me if you want more info. the advantage is not small. Oh, and be sure to run the Sonicap Platinum .1ยต between the positive and negative poles of your Elcos. Write me about that too.
It is important to realise that switching amps use one of a variety of different designs, there isn't a ubiquitous Class D design just as there isn't for SS or tubes. The issue about loads applies to some of them, not to others. I have tried Ice modules, UCD, and Nuforce and while they all have the benefit of not suffering the characteristic sounds of SS or tubes, they nevertheless had definite different characters. Studying their designs it becomes obvious that their designers each chose a different set of trade-offs, and by the way each has a readily identifiable design weakness of some type. The present is bright already for these designs and the future looks even better as it seems to me that the application of a bit of art to the basic idea will push them well past SS and tube amps over the next decade.
Martin Colloms is a highly regarded & respected reviewer. I agree with his asessment that Class D amps don't quite measure up to audiophile use but they are fun toys. I've tried a few of the above mentioned/reviewed Class D amps and have sold them and have gone back to conventional designs.
Our collective point is, Phd, you can't just try a class D amp, It takes a commitment to find out what brings out any class D amp's best. Some folks are lucky and have equipment that works well with their new amps. Others have hose cables, high impedance preamps, bad performing digital, or unshielded power cables, any of which can foul the sound.

I want to get a copy of Mr. Collin's article. I don't know about others, but my system would cream anything he has that uses his favorite conventional amp.
Muralman1, that is a good point that experimentation & patience are important to get the best results from Class D amps. I know that some class D amps are transparent as hell but what I didn't like is that some designs lacked body, that weighty full sound you get from conventional amps, but all class D amps are not created equal. Also it has been mentioned before that class D amps should not be compared to analog and should soley be judged on their merits as a somewhat new technology.
"I want to get a copy of Mr. Collin's article. I don't know about others, but my system would cream anything he has that uses his favorite conventional amp."

<---- Good lord your a loonie!
Nuforce as a company does not consider there amps as digital, they call them analog switching amps with very high bandwidth, low distortion.
In my system the lack of body is not a issue. in the end its the same song what works for you is all that matters. and until the cows come home there will always be those who reject anything thats different than what the norm has been.
Florian, Looney (proper spelling) is the guy who figured out who Shakespeare is. I agree with him, and proudly wear the looney label.
Phd, wanting "body" in your playback is, of course, a valid desire. Big AB amps are the best for that. Class A breaks down the body into mellow details. Tubes take the dissection further. You simply hear more of what is recorded. Great class D will completely disassemble the body into it's respective parts. A well set up class D system will resemble a great SET system in detail and proper timbre, only the class D will be more dynamic.
Let's say you've got a hotrod with a high performance engine. Maybe this engine has an old school fuel delivery system. Maybe you'd like to update the fuel delivery system with some new technology. You cannot expect maximum performance by simply removing the old fuel system and installing the new one. You're going to have to put in some time and make some adjustments to the rest of the system to realize the fullest potential of the new technology. What those adjustments will be are going to be determined by the rest of the rig and of course your own personal needs and preferences.
Those of us that have switched to Class-D amps and have put in the time and made the adjustments to the rest of the system are being rewarded accordingly.
Like many others who have responded, my rig has never sounded better or performed more efficiently than it does now with the Class-D amps.
I've had a lot of different gear and regardless of how good any of that previous gear was, none of it has delivered the goods like the goods are being delivered now. I've experienced absolutely no downside whatsoever by making the change to Class-D...only positive.
These amps take up substantially less space, they use a lot less power (my power bill went down $14.00 a month simply by changing to these amps), and they put out virtually no heat.
At the same time they have over twice the power output of my previous room heaters, and they are more neutral, more dynamic with better detail, faster and they have more body. I'm sure I could list other attributes but you get the idea.
Regardless of the item or the topic, there will always be those that cannot or will not accept that something new or different could possibly be better. Is it going to be better for everybody...probably not. But that doesn't mean it can't be better for those willing to give it an adequate chance.
I for one could not be happier that I made the change and put forth the time and effort to optimize that change. I will not be switching back and I think as this technology becomes more refined we're going to see a lot of others making the switch as well.
This has really been an interesting and enjoyable thread and one that I am following closely. I'm glad to see so many responses and equally glad to see that I don't stand alone in the Class-D camp.
Keep it fun everybody and enjoy the music. I know I am!

Looking at this thread as a whole it seems to me there are fewer class D detractors than in months past. The few that are here have at least had some first hand experience with the a product and politely didn't care for their presentation.

After looking at the Colloms review I must say he presents very convincing case for someone who maybe thinking of crossing over to the D side. Which in itself has me wondering why would anybody put that much effort into disparaging the performance of these amplifiers. My first thought was to support and clarify the TAS shoddy shootout. Whatever his reasoning is, what does the audio press stand to gain by labeling class D as not HI-FI?

Well said Mjvfashion.

However I simply installed fuel injection on my engine and it was instantly better. No need for new plug wires or a new cam!

Maybe I am just lucky. :)
Kudos Mjfvashon! Well said. A power amp, bottom line, will only amplify what it is feed. I believe the knocks against early CD is that it was solid state shrill. Vinyl did sound better through solid state pre and power amps. Time went on, improvements were made. I know people who will still only listen to vinyl through tube equipment. I think the best improvement a person can make in their system is to have a tube pre-amp or a tube DAC. J. Gordon Holt, once said the best combo was a tube pre with a ss power amp. I took that advice and I will always have a tube pre. As stated in a previous post, I now have a Tripath based power amp and I have no plans to replace it. My system has never sounded better.
Wow! We all know our own equipment is a matter of our own taste and personality. Most of the time when we give our opinion when asked on this site what is better or sounds best we add the IMHO. We all have opinions most of us just don't get paid for them. For some reason if we are paid and published it seems to matter more. I value members of the Audiogon community opinions much more then one single minded reviewers opinion.

Just like mentioned above, "new technology gets it hard like when solid state was new". Remember when CD players were still developing in the late eighties? Philips came out with their TDA1545A 16 bit dac chip. People liked it, but wanted better. Now many designs are being designed that sound better then anything else using this chip. Zanden comes to mind here, if you want a TDA1545A-S2 chip it will cost you $200.00 for just the chip.

My point is in 15 years we will be trying to find these current class D amps because they sound so good and the new technology will be the argument.

I changed from $8K Melos separates to an $8K integrated to a class D amp and tube preamp because it like it.
to anything else I've heard.

There are a lot of switching amps that are poorly designed and that do not manage RF noise. Using a switching power supply saves weight and cost, but places a major noise source next to the amplifier circuitry. It takes a lot of design effort to reduce the effects of this noise, but the effects cannot be made as small as if the power supply is a good linear design.

Colloms commits the error of hasty generalization by blaming the approach for the consequences of inadequate design.
I thought the power supply was built into the circuit boards on these amps. I'm new to this, but aren't most of these products just the B&O board inside a fancy box? For those manufacturers that use the B&O kit, what differentiates their amps?