Hi Atma, I do grant you that these show hotels seem to have lucky spaces and very very unlucky ones. Trying to Tame the wildness of some suite I am sure must be a frustratingly thankless task. . . . perhaps as easy as herding cats?! Is one of the problems that you manufacturers end up having to select a room from a floor-plan without having the opportunity of sonically testing the space ahead of time? Perhaps RMAF organizers should be encouraged to assign some of the odder sounding rooms to the admittedly few static displays. . . do not need good acoustics to select LPs from a bin, after all.
Back now to the discussion of artifacts and stereotypical audible flaws in switching amps, without here pointing fingers to models/brands in particular, I observe that that there are a number of such amps today that do still sound stereotypically 'digital' to a slight or greater extent. Among 'non stereotypical' switching amps, I have already waxed poetic on this and other threads about the two switching amps that I truly like as of the end of 2007. I should also point out though, that I have heard switching amps that did not seem to have any audible 'digititis', and still I was not able to like. In one particular case, the sound of one seemed overly dark to a fault, almost if the designer were attempting to overcompensate for expected stereotypical flaws. not sure if I was having a bad audio moment or I was perhaps in a 'dark' sounding suite. I did discuss the device with other audiophiles that have listened to it under various circumstances and received confirmation of my cursory impression.
As you said, the switching technology is young and evolving rapidly. It's certainly worth watching with an open mind. It is equally true that it may in the end turn out into the proverbial flash in the pan. . . and 10 years from now, instead of having grown to broader maturity, it may be simply remembered as a valiant experiment. We will have to wait and see. |
Guidocorona, just what will be the standard, if class D never ascends to superiority? Solid state, with it's manufactured. "Body," and smeared highs?
Or is it to be NOS tube amps, with their rapidly dwindling stocks of tubes, and their cloying delivery, the worst of which sound gooey with caramel?
My class D amp. augmented with the perfect preamp. is deeply detailed. hugely dynamic, sweetly extended, and lifelike, superseding every SET or any other tube system I have heard. Solid state might as well skip the party.
B&O has announced a new generation of digital power supply modules that purport to have have distinctly improved stats. Someday their modular amp will succeed in making even the now so necessary analog power supply superfluous.
The future is here. It's just the learning curve on how to implement class D amps that is in it's infancy. |
high muralman:
the alleged superiority of class d over tubes or tubes over class d cannot be confirmed unequivocally.
i cannot corroborate your perceptions, you cannot confirm my perceptions and what is better or worse is a matter of opinion. we can agree to disagree. |
hi guidocorona:
i have attended ces shows since 1992. i have yet to hear a class d or solid state amp that i would want to own.
i have not heard any class d amp i would characterize as dark. of course the sources that i used to evaluate stereo systems were probably different from what you auditioned.
i am still curious as to which brand(s) you found "dark" sounding. in addition, i am also interested in the names of other components and stereo systems which you consider to be "dark" sounding. |
Hi Vince, excellent point about dwindling NOS tubes. . . eventually these animals should be declared endangered species and given a modicum of protection against careless use by heartless audiophiles!
You have good chances of being correct about the future of class D amplification. Yet, it is a lot safer to study evolution with hindsight than using foresight. . . . at least for old and crotchety 'secular humanists' like yours truly. Perhaps 65 millions years from now some bookish techno-paleonthologist will examine the then famous Silicon-boundary layer in ancient petrified garbage dumps an discover an explosive growth in the fossil record of switching amplifiers. And perhaps a fossilized 'organism' with an especially unusual body plan sporting a transformerless combination of pre-silicon B-300 tubes and primitive switching amplification modules will be uncovered. . . a brand new techno-phylum will be assigned to it. . . and the specimen will be named Hallucigenia Atmaspherii by its discoverer--an incredibly distant descendent of Aloysius Qwantz Schmaltzenstein Gavronsky. |
It's kind of silly to have to drag out the "dwindling supply of NOS tubes" argument. There are more tube manufacturers than 10 years ago thanks to the music and hifi industries, and MANY manufacturers (basically all) use current production tubes and get excellent sound from them.
Yes, you can likely improve the sound with some pricey NOS tubes, but the costs are going way up and you tend to simply change the sound with differing tube brands and vintage, not always for the better. I have a pretty good stash of NOS tubes, but I could live just as happily if my rig was running current production stuff.
RFG |
We have an internal design rule we call the 20-year rule that prevents us from using NOS tube types, IOW the tube type has to be in current manufacture. We've had this from the beginning, so its already served us well, as we have an aggressive update program for our older products.
Its a simple fact that semiconductors go obsolete and out of production at light speed relative to tubes. You can still buy new manufactured tubes that were designed 60 years ago, but I can think of quite a few semiconductors designed in the last 10 years that are already long gone.
The 'dwindling tube stock' idea is a red herring, unless a manufacturer has chosen to design around a tube that is no longer made, a foolhardy undertaking.
As a lot of the current class D amps are on monolithic modules using proprietary semiconductors, you can expect that if you need to service the amplifier in 10 years or the like that the device is going to be tricky to find. This is one sure way of knowing that the technology is still on its way up.
To get a better understanding of this, an example of a mature semiconductor technology is the lowly op-amp. You can still buy TLO82s brand new, despite their having been designed in the 1970s.
How many people on this thread think that they will have the same class D amplifier ten years from now- knowing full well that in far less time than that their amp will be superseded? |
Guidocorona, fellow secular humanist, you are right about the futility of guessing evolutionary trends. I am sure you picked up on that fool's recent surmising there will be two races in 250 years, tall and swarthy haves, and ding dong dwarf have nots. Who can say? Given the world's species environmental peril, I have darker predictions.
Just the same, I think if I were a struggling proto-mammal 240 million years ago, after spying a sleek early dinosaur..... I would put my money on him to rule the world for the next 200 million years. Don't you think? :D |
"How many people on this thread think that they will have the same class D amplifier ten years from now- knowing full well that in far less time than that their amp will be superseded?"
Excellent question Atma. . . and I should add, How many people on this thread think that they will have the same class anyclass amplifier ten years from now- knowing full well that in far less time than that their audiophilia will have the better of them and will force them to 'upgrade'? Only I, and very few other rabid audiofools, keep amps of any kind for 10 years, B-300, Mos FET, ICE, Doppler eliminators. . . or otherwise. |
Very interesting debate. For the most part conducted in a thoughtful and considered manner (not withstanding the usual sarcasm from he who must not be named). We can attempt to guess the future but that is a fools game best played by fools. Digital amps are here to stay and the technology will only improve. The fact is they are gaining market share and they are converting many audiophiles into believers.
I have spend many hours listening to Bel Canto amps (the new Evo 1000's) and they are in a word MUSICAL I also have many hours on the older EVO 2's which were (if you believe reviewers) a class A rated product. Debating these amps subjectively (against tube amps), while somewhat useful, is like debating how many angels can dance on the head of a pin.
From a design point of view the Bel Canto line is a home run and the modular look and concept appeals greatly to young professionals ---and is wife friendly. Who knows, it may even save a few marriages as tubeaholics partake in a mass conversion.
In a hobby populated with insane pricing and cables that possess magical propertties I for one like what I am hearing. In case you think I am a Bel Canto spokesperson or salesperson ---I am not. However I will give credit when it is deserved. Seven years ago Bel Canto was primarily a vendor of tube equipment. Before you could say "Class D"
they had, quite literally "switched". Pretty gutsy don't you think? Yeah, I can hear "he who must not be named" frothing at his bit "they compromised to follow the money trail". Probably. And I hope so...
Lest you think I am a nerdy computer geek who who dislikes tubes or audiophiles then think again. I am a 52 year old vinyl junkie and confirmed tube man (Wyetech Pearl pre and Wyetech monoblocks}. I love tube rolling and am a great fan of Ralph's OTL amps; as many of my friends own them. Yes I have paid the power company mucho dollars to run my equipment and participated in many sweat soaked listening sessions during the hottest days of summer. Yes I have diligently sought out NOS tubes and paid dearly for the honor.
I knew change was afoot when my friend called me up and said the furnace repair man took one look at his rather elaborate tube amps and asked what the hell are those things --- a freakin bomb!!!!!
Like the magazine says-----enjoy the music and show a little respect. And don't believe everyyhing you read particularly in a stereo magazine.
Cheers |
Sure they can sound good,but why oh why did they all get such a terrible low score?Not even in the 40's ,50's,what 8,10.13?Mid fi at best |
I'm quite happy with my class d amps. Yes the manufacturer offers upgrades at a not so out of site price. Yes i have upgraded twice, Yes each time my amps have increased in there ability to make music better. And yes i use a tubed preamp for now with my class d amps. A bit of the old with the new. For the life of me i cant understand why some have to believe that what they like is the only thing thats any good. Guys and gals if you have a amp and system thats to your liking i am so glad for you. Dont argue that its better than mine.
Enjoy your system and i will enjoy mine. |
Mid-Fi huh. . . Oh Dear. . . I really did not realize the horrible implication of those scores! And I have been all along singin' the virtues of mere mid-fi trailer-trash electronics. . . how could I? What are my neighbors going to say if they only find out what questionable company I have been keepin'?! . . . I's so sorry I's so sorry. . . I really didn't know nothin' none of it! |
Coffeey: "Sure they can sound good,but why oh why did they all get such a terrible low score?Not even in the 40's ,50's,what 8,10.13?Mid fi at best"
I think "4" might be better. Then the Accuphase A-50V should have a "3" and the Mark Levinson 333 a "2" :)
Chris |
I will preface my remark by saying I have not listened to any of Class D amps except at a couple of the Audio shows so I won't attempt to argue or debate the issues of sonics but to follow up on Ralph's (Atmasphere) points; I don't think Ralph thinks/thought that we (most audiophiles) would in fact have our amps, pre, DAC's etc for 10+ years, although we certainly could if we got off this merry-go-round, Ralph knows the Audiophile weaknesses. The point as I see it is, tube amps will have value after that 10-20+ years where the "D" amp will be worth 000000. No one will be able to service the "D" amp if one of the chips or digital circuits should fail. At that point the amp is worthless. Case in point, I have several 50-60's Fisher, Scott, and Marantz pieces that are worth more today than the day they were sold new and in the Marantz case many, many times its original value. If I can't fix these pieces most qualified techs can get them back up and running.
Ralph if I have miss-interpreted your point please correct me............Bob |
In an attempt to refocus the discussion, I'd like to point the gang to the recent blog followup by Martin Colloms:
http://hificritic.com/Scene/news.aspx
In his post Martin lists 17 different measurable flaws he seems to have uncovered in the reviewed samples. I have heard only the current version of the Channel Island amps and the older Evo2 series of Bel Canto, while I have not heard the latest Bel Canto series nor I have any experience at all of the other two brands. I admit I have detected some slight artifacts in the Evo 2 and perhaps more so in the Channel Island which may be congruent with his observations. The problem in his analysis is rather that -- once again -- he jumps to generalizing conclusions by extending a priori these flaws to all and every switching amplifier implementations on the market today. I have no qualms with his analysis. . . the problem is all in the logic of his induction step. |
While I have not A/B'd the "new" hi-tech "class-d" designs with any other amps,this discussion is becoming a bit silly.
The audiophile attitudes toward one's own particular set of "what one likes" should not overcome the "obvious",which is 1...Progress(like I stated earlier,this will not even be a discussion in the not distant future).#2...the fact that there is a growing contingent of music lovers who hear enough of Class-d's virtues to invest in them(they cannot be all deaf).3#...the arguement of the tube afficionados(of which I am one,btw)remains consistent,regardless of technological or performance improvements.#4...With the HUGE advantage of LOW heat(actually almost none),low cost,and small size one has to be really foolish to believe that a "matured" Class-d design(sounding great,by any standard)is far away.
As to obsolescence.....PLEEEEEASE!!!By the time a really good Class-d design is ready to get "dumped" by a particular owner(unless one is on the non stop merry-go round)what do you think the price of GOOD NOS TUBES will cost??Sort of makes up for the costs of new amps,almost!Based on the going trends!
BTW,I have no interest in buying anything,in the near future,but like to think I am open minded,and still have some pride in my current hearing!
My Tube loving friends have been almost militant about any other design formats.To my way of thinking it is their loss. |
Sorry!Forgot to mention that companies like Nuforce allow for "upgrading" to new technology for reasonable prices.You are not going to have to worry about obsolesence with this type of policy.
As stated earlier,I don't own a class-d amp,but why shouldn't I be open minded to a good thing?The systems I have heard,employing them sounded just fine!
Best |
Golden words Sirspeedy! Militancy of any denomination narrows our perception of reality, our ability to learn from one another, and ultimate to enjoy the fullness of life, including our hobby! |
I agree with Guidlcorona. Sirspeedy, that was a good one. My amps have been serviced, and upgraded twice since I bought them three years ago. |
Colloms, my thoughts exactly. Having tried a small group of Class D amps, extended listening resulted in my dissatisfaction in several areas with all the amps. Of the group that I listened to, I owned the CI D200 amps the longest (several months) to get a pretty good grasp on their performance.
They did do some things well enough (but since I don't factor in weight, size, appearance or power consumption) in the end these amps did not do it for me either. I have moved on and not looked back.
I do believe; however, that there are several companies making these amps (which are quite inexpensive to mfg) due to the rather high margins, low cost of mfg., and current high demand for profitability purposes. I see no fault for doing this as it is what the public seems to want at the moment. And, this is the history of the industry.
I think to build these amps properly, to deliver acoustically, will prove to take more money than just the sum of ordering various off-the-shelf parts from parts distributors that achieve the high margins and immediate sales opportunities present today.
In the long run, fine Class D amps will be designed and built and available as an alternative. However, when this happens, all these cheap, mediocre D amps will be available for literally pennies (ie. $0.05 to $0.10 on the dollar). Some of these better Class D amps are finally starting to show up.
I would not rule the technology dead, but for me, I have not seen the light, the parting of the sea or the supreme acoustic deliverance that others are reporting.
The truth is the only person's opinion on equipment performance one should care about is their own (or perhaps other close family members that share in the listening).
I still own 2 class D amps. Paid $20 for each of them and they are fine for my patio/deck and my 11 year olds sons bedroom. I have come to my personal conclussion that the power supply is such an important aspect of good amp performance that it will take a lot of careful examination/audition/review to try another Class D amp.
I am suspect of the reviews, especially those in the rags like Stereophile where every product they review for the year ends up in their "Recommended Components". |
As a CI D200 owner and lover for the last two years, I find it quite interesting that these amps very rarely come up on the used market.
In fact, I'd say of all the amps mentioned in this endless thread, the CI D200 are by far the least seen on Audiogon.
Given the number of these amps out there, I'd say that's the ULTIMATE test of actually how good an amp is, is an owners complete satisfaction and not wanting to sell it in an attempt to upgrade. |
the satisfaction of an owner of a component is not a predictor of the satisfaction of a potential owner of that product. |
Confucius has nothing on you Mrt. |
Partially agree with Atmasphere on semiconductor comment.
I've done some work in my SS class AB amplifier, I have the service manual and parts such diodes, transistors, capacitors (i.e. things that are most likely to break) aren't hard to come by at all.
I agree with you thoughts about class-d though, they have a lot of IC's and surface mount devices. Even if you do find the part you need, installing it will be a pain and expensive (if you choose to let a shop do the repair work for you) |
Mrtennis...Not an absolute predictor, but a useful indication. Why else do we contribute opinions, pro or con, on this web site? |
I've been mightily impressed by the sound of the Rowland Concerto intergrated amp driving various Vienna Acoustics speakers. Some time soon I plan to put one in my system, against my old Bryton 1B/2B system and also compare to Conrad Johnson that my dealer carries.
I'm not worried about what some twit wrote. I trust my own ears, after 50-years of trumpet playing and about 43-years of audiopilia. Early signs are, to me, Class-D can sound very good.
Dave |
Dstep, your post is like Music to my ears! I have heard at some length the Primare CD21 + JRDG Concerto preamp + JRDG 312 + Vienna Mahler combination in the Soundings/JRDG suite at RMAF two years in a row. The sound was awesome with IMO unparalleled musicality. . . so much so I have suffered a major audiophilic breakdown during the Summer. . . and as a result just last week I have taken delivery of a brand new pair of Vienna Mahlers. . . . . . . A new amp will hopefully replace my trusty old JRDG Model 7M monos this time next year. . . Have not yet made up my mind completely, but Rowland 312 and Spectron Musician 3 Sig are currently high on my prefs list. |
Hi there Guidocorona. Soundings is where I first heard the JRDG monos about three years ago, driving the Strauss. Being in the midst of moving from Dallas to Denver, I set my mind on the Strauss in a large basement music room. The soft real estate market has kept me from leaping into a house and three years later I'm still in a nice high-rise apartment in DTC.
This summer I finally decided to reconsider my speaker choice a chose something that would work in my 2100 sq ft apartment and took the plunge with the Beethovan Baby Grands. (I'm entirely happy with that choice).
Anyway, the second time I heard the JRDG equipment/Vienna Acoustics combination was at the 2006 RMAF. After a day of bleeding ears, hearing horrible set up after horrible set up, I stopped by the Soundings/Sumiko room where Rod and his boys had the Rowland/VA setup. Oh what a relief to the ears. Those guys know how to set up a room. They start with good equipment and really get the most out of it. I'm sure that lots of the other exhibtors had very fine equipment, but most of it was unlistenable to me, most likely due to poor setup.
I've about got the Beethovan's broken in and my new Pro-ject RM10/Blackbird TT/cartridge setup. Late this month I plan to have Rod over to optimize my speaker placement. After that in December or January, bonus dependent, I'll be doing the JRDG/Conrad-Johnson/Bryston comparo. It might be easiest to do a JRDG/CJ comparo in-store and then bring the winner home to compare to old faithful Bryston. (Evidence is showing the Bryston pretty darn good; however, I found the Pro-ject Tube Box superior to the Bryston's onboard phono stage, though it didn't blow it in the weeds).
See you around maybe.
Dave |
Hi All,
I'm in the midst of a home evaluation of a Spectron Musician Signature 3 with MBL 101e's. The preamp is an MBL 6010D. My current amp is a Boulder 2060, and the reason I'm looking for a new one is that I changed to a computer-based USB DAC by Wavelength Audio. When I changed, something went missing. That thing was bass dynamics. Not bloated , flabby bass, but the clean punchy, articulated bass that provides, for me, the foundation for the music. Bear in mind that this eval is in my system,in my room, using my ears, blah, blah, blah.
The amp is, in a word, spectaular. The images which were kind of thin, have become fleshed out and solid. The drums kick you in the chest. Vocals are to die for. The only thing holding me back is further evaluation of the delicate, nuanced highs that you only hear with a deep black background. I'm still going through my recordings for pieces that highlight those moments. I'm pretty much sold. For $6500, it is a no-brainer. Spectron says that they have many people using them with MBL's, in stereo, not mono config. I have the amp for 3 more days.
David |
Welcome to the club, David. I knew it was just a matter of time. |
"After a day of bleeding ears, . . ."
Dstep, have you and I perhaps purchased our ears from the same supplier of auricular equipment? My general experience is same as yours. . . lots of ear bleeders at RMAF; but each time I returned to the JRDG/Vienna/Primare Soundings room for one more hour of music, I felt I had 'come back home'! |
Hi Deshapiro, very interesting, please tell us more once your eval is complete. In particular Spectron/Boulder comparative findings about extension/delicacy of treble, bass extension/tunefulness and control, overall harmonic development and decay across the range, low level microdynamics. staging, hall ambiance, headroom. |
I'm happy that John & Toni are finally getting the recognition they deserve. They are a class act! I had the Musician II, which I had some problems with and they were very accommodating and made me upgrade to the then new Musician III for a very good price. I guess after all the good press that the Musician III SE is getting ,it's time for an upgrade! Damn, I got to stop reading these forums. |
hi eldartford:
an opinion is very subjective. i don't think that popularity or the satisfaction of other owners is a reason to buy something.
as has been said many times, your ears are more important than any opinions.
the only question is, how to minimize the number of components to evaluate.
i'm afraid one should audition every component in one's price range, depending upon preference for, say, tubes or ss. |
DeShapiro welcome to the D side. I've envied your systems for some time.
Vic |
Guidocorona - Hi-Fi critic is wrong on all 17 points he presents. Class D produces only about 1% of the carrier (usually 0.5MHz) on the speaker and practically no switching noise (zobel network). My Rowland 102 is directly under TV - no problem. At 0.5MHz speaker cable needs to be 150m long to be 1/4 wave antena. Class D Amps cannot be "unstable" (big advantage) because by definition they oscillate (analog modulator). They are in reality high power sigma delta modulators. It is important to realize that most of modern dacs (sigma-delta) are working on principles of class D (PWM) - same with SACD (PWM at 2.8MHz). I read a little bit of Karsten Nielsen doctorate work on Icepower (University of Denmark) - very interesting. |
I really wonder if Martin Collums has deliberately written such a controversial overview as a means of getting publicity for Hi Fi Critic.
I am still undecided about Class D amps.I have heard some that certainly lacked vibrancy and image depth but I have also heard a Nuforce 9 V2 that I thought sounded very good.
I would say ,on balance,better than any transistor amp I had heard.But then again I really don't care for the sound of transistor amps.I much prefer tubes and gainclones.
Mr Collums background really needs to be considered.He is obviously a critic who likes the sound of transistor amps.
I think many people who like Class D are also people like myself who do not like this sound and are looking for something with power but with a different type of sound[something more organic?].
When he was writing for Hi Fi News he recommended amplifiers like the Naim Nait 3,Naim NAP 180,Audiolab 8000S and Exposure XX-all amps that sound very coarse and "transistory" by todays standards.
He also has a long association with Musical Fidelity.I believe he designed speakers for them.So when he uses a MF amplifier as a reference and describes its superority to the Class D amps ,questions about bias or cronyism probably need to be considered. |
I'll have more impressions in a few days. Meanwhile, does Halcro fit in this discussion, price excepting, of course?
David |
Hi Dave, I am not aware that Halcro amps are switching amps. . . but if you have any comparative findings of Halcro with Spectrum, that would be interesting. |
While I don't depend on Martin Colloms to make my decisions for me, I've come to respect his views. Mr. Colloms is hardly a reviewer that just likes "transistor amps". In as much as he has historicaly praised classic ss amps like Krell, he's just as often consistently offered kind words for classic tube amps like conrad-johnson. That suggests to me, that he has a fairly open mind and can find the qualities in amplifiers regardless of the technology. I haven't read his reviews re: switching amps, but I applaud the undertaking. My own, very limited (let me stress limited) experience with this new technolgy, suggests that they aren't quite at the forefront of amplifier sound, but, have demonstrated remarkable potential. I believe "digital" amps just might be the choice in the future on sound quality alone, never mind all the other inherent benefits. |
If Martin Collums does not like the sound of switching amps that's his right, but his 17 points are garbage. He thinks that switching amps are digital and have limited resolution (like in 60's). He claims that switching amps have "fragile output devices" where in reality they are more robust than class A/AB amps. For instance output of Icepower contains H-Bridge of 4 very strong Mosfets with all sorts of protection. He writes nonsense about power supply folbacks and heat dissipated in output devices. He appears to have no education in electronics and his statements are pure demagogy. His points about usage of negative feedback, high output impedance or "clipping" are all nonsense. He is right about soft clipping - B&O added it to protect tweerters from possible high energy during overdriving (Class D has a lot od power). He makes it sound bad but it is a virtue. Many traditional amps have soft clipping (NADs for instance). He mentions high intermodulation distortions where in reality it is just opposite - having no nonlinear output devices does not suffer from IM (Icepower 200ASC has 0.0005% IM at 10W 4Ohm 14kHz/15kHz). I could discuss every single point he makes - all of them are garbage. It is much better to say "I don't like the sound" instead of making uneducated false claims. |
Kijanki -> may I ask where are you from ? Are you from Denmark ?
I'm asking since B&O, the maker of ICEpower modules is from Denmark as well, which in my view may influence your opinion (call it a local patriotism). |
No I am not from Denmark. Nielsens doctorate is available on internet. I own Rowland 102. At first sound was a little "lean" and sharp but over time it mellowed. It needs a little more "chestiness" (lower midrange) - improved after switching speaker cables to Acoustic Zen Satori. Transparency and Clarity is great. Bass performance is outstanding. Stereophile, 6Moons and others had glowing reviews of different class D amps - also Channel Islands D100 (based on Hypex modules - and no I am not Dutch either). The very best class D amps are probably Kharma (not Icepower) and Red Dragon (both too expensive for me). Sound is a matter of taste (so to speak). There is no rights or wrongs. Tube amps producing/exaggerate even harmonics sound wonderful on guitar or voice but horrible on instruments with more complex harmonic structure like piano. Piano structure is a little like percussion instruments that not follow simple harmonic structure and often sounds "out of tune" on warm amps. I prefer neutral amps. The question also should be "what is best for the money" - class D is difficult to beat. |
I think Kijanki is right: Martin Colloms' statements about the 17 weak points of class D have no solid scientific foundation. I wonder where he gets such information.
Chris |
Kijanki, I agree completely- and will add that many of today's specifications exist to sell certain types of amplifiers rather than get to the truth of the sonics. |
Elberoth2, I don't know where Kijanki is from, but would I be in my more waring moods, my argument would parallel his, for the most part. I live in California.
Not having heard ICE ASP module, I can't comment. Their 500A, mated with a great linear power supply can put your system in just this side of heaven made. |
Kijanki - ok, fair enough. I would like to know though, why do you think that:
1. Pushing broad band radio frequency noise into the power supply outlets
2. Pushing broad band radio frequency noise out of the line and ground connections
is considered OK by you. Those are just two first Colloms points. You said they are rubbish. |
There are 3 kinds of switching noise in Class D amp:
Carrier frequency - approx 0.5MHz
Switching spikes of output Mosfets - approx few ns
Switching power supply frequency approx 50kHz
Carrier has very little chance to get thru linear power supply with all capacitors then power transformer and finaly input chokes and capacitors (pi filter). It has even less chance to get thru regulated switching power supply (my Rowland).
Switching spikes have very little energy and are filtered on power supply as above, and on the speaker cables by means of common mode chokes and capacitors (zobel network).
Carrier in not completely filtered on speaker cables (about 1% left) but needs 525 fett of speaker cable to become 1/4 wave antena.
Switching power supplies are present in probably every modern TV set and are strictly regulated. Not only that my Rowland for instance has CE certification (part of which is measurement of radio emissions) but also Icpower module used inside (200ASC) has folowing info in the datasheet:
EMI conforms to: EN55013
EN55020
EN61000-2
EN61000-3
FCC part 15-B
Elberoth2 - There are few early amps with poorer filtering like previous EVOs (not Icepowers) from Bel Canto or some NuForce amps but he implies they have poor performance because of it or that the company performs some illegal acts designing the switcher.
His point 1. is practically same as ponit 2. It is not possible to push noise out without pushing in - it's the same thing. He just makes it sound worse. |
Eleberoth2 - let me follow on this.
In point 3 he mentiones up to 2V of 50kHz frequency on the speaker cables - complete nonsenese - unless he talks about normal audio signal (my Rowland ha -3dB at 65kHz).
Point 4.
"Make the output impedance, a passive filter, variable with frequency and dependant on speaker loading."
I design electronics for 30 years but have hard time to understand how passive filter is variable with frequency. There are common mode chokes and capacitors on the output (zobel network) but they are present in most of other amps. This filter is set to about 65kHz (-3dB). Filter is within negative feedback and damping factor for Icepowe is about 4000. Early amps on Tact modules had output filter outside of feedback - but he makes general statements.
Point 5.
"Allow the amplifier to be marginally or completely unstable with high or open circuit output loading"
Complete nonsense - since switching amp is constantly unstable (cannot become more unstable - big advantage) being analog modulator/oscillator.
Point 6.
"Employ soft compressor clipping circuits prior to full power clipping"
Yes it does - (big advantage) designed in on purpose to protect tweeters from high energy during overdriving input. Many amps (like NAD) have this advantage
Point6.
"Employ high order negative feedback to improve in-band distortion figures"
Every amplifier does this either with global or bunch of local feedbacks. I know about multiple feedbacks in Icepower but suspect them to be shallow since output is pretty linear. I don't know how he knows about high order but Class D is different creature and has different feedbacks. He might be implying deep negative feeback - usually bad because of TIM distortions but there is no need for deep feedback and even if they put one in it cannot cause TIM. TIM comes when feedback cannot react fast enough and output transistors go to saturation getting charge trapped at their junctions becoming immune to following signal for a while. In Class D output transistors work differently (switching) and are respodning to time not voltage.
Point 7.
"Use feedback to provide numerically high damping factor at low frequencies and claim that this guarantees fine bass.(regardless of the interface to the loudspeaker)"
Isn't he implying by word "numerically" that this damping factor is not real and manufacturer is not honest. That is what I call manipulation. He makes impression of poor bass performance of Class D - this won't fly either. Enyone who listened to Class D amp knows tahat bass performance is its best feature.
Speaking od damping factor - my Icepower has 4000 and probably unnessesarily since inductor in series with woofers has obout 80mOhms and limits DF to 100. At 20kHz similar limitation is imposed by about 0.2uH imductance of the speaker cable. DF of 200 would be plenty. |
