Class D,T or whatever (pwm amplifiers)

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Hello to all,

Just thinking about to start a new thread about PWM amplifiers in general in every kind of form.
I recently saw some new developments on Class D and maybe its a challende for every DIY er to try for themselves to build one.
Ok, we all know about the pros and cons about class D amplifiers, but also do know that electronic components are getting better with higher switching frequencies.
The amount of webpages are increasing too on that subject, so food for thought...
Class D/ PWM amplifiers

Guess every one is busy recycling old JLH,Mosfet,Pass amps without trying some new technologies, for instance class D or other variations.
Wouldn't it be nice to finally design an amplifier which is not producing heat, but just amplifies the signal without too much hassle?
What about the technology Mr.Carver is using?
Or are we narrow minded just re-inventing the old class A,AB,B designs from 40 years ago..
Class D amplifiers are efficient, but have never risen above mid-fi in sound quality. Since they slice and dice the signal, they are at their best with lower frequencies. Once you get into the midrange and upper frequencies...forget it.
If you're into light weight, efficiency, or quantity instead of quality, go for it, but if it's good sound you're after, you'll need a class A or AB design.

Class D reprise

So you can scrap the CD player aswell? It's also working in the digital domain...
According to the last statement(GRollins), only analog recordings are for real...(because they are not slicing)
Why using still the old prejustice against new technologies,because you read it somewhere? Is the solid state forum really going down hill?

[Edited by HaaiFaai on 11-24-2001 at 10:23 PM]

>> Why using still the old prejustice against new technologies,because you read it somewhere?

If you are looking for information, why do you keep trying to instigate an argument?

Have you listented to these amplifiers?

Or have you just read it somewhere? Obviously you have not read enough, as finding relevance between GRollins comment and CD players is pretty asanine.

The solidstate forum is going downhill because of people like.. oh forget it. Happy DIYing..
Class D

No I am not working for such company, I give up trying to
see if there's a discussion possible.Obviously no one ever
tried to build such an amp.Ok I admit it wasn't the good way to start, but if in the solid state thread I only hear about bulky transformers, seeing most of the time the same questions. I also care about the good old class A/AB technology, so many things about those amplifiers are already known, so I was curious about other ways.

Sorry I didn't work out. (Sorry that I offend someone)

Whilst I would agree with you that recently the overall forum content appears to have degenerated somewhat and that certain posts would be more appropriate at another Asylum, sorry forum, that shall remain anonymous, we should not denegrate those who hold alternative views however misguided these appear to be. Also, allowances must be made for those for whom English is not their first language and therefore perhaps appear to be argumentative when in fact they are seeking to open a debate.


You refer to predudice against new technology. This is probably not the case for the majority of people who visit this forum. We are looking for the best possible sound reproduction (within our own particular constraints such as cost) and if new technology can give us an improvement then we will embrace it wholeheartedly. However, I have yet to hear a Class-D amp that is anything other than, as Grey described it, mid-Fi. Improvements may be made in the future, but in the meantime I for one will stick to traditional forms of amplification. If the classic designs from 40 years ago are more pleasing to listen to than the modern high-tech circuits then these are the ones to use, though this depends upon whether ones hobby is the pursuit of aural pleasure or the satisfaction of owning the latest technology.

Dear all,

thank you Geoff for your views about language. Many people in english speaking countries ofter seem to forget that it not spoken by everybody in the world (why do we not speak chinese ? ) and it is not always easy to express probably controversial meanings with the "appropriate" courtesy or sublety. English is the language of this forum, like of anything else in the WWW, but is not my mother tongue, I need far more time to read and write posts than others. Whilst some try to read a possible "subtext" others struggle to understand the basic meaning perhaps. So let us all be patient and tolerant. This also refers to humour and sarcasm for example, that can be "tricky" sometimes.
I often had the opinion to be misunderstood somehow by members of this forum, and I suspect it was just a subtle "mistake" or typo by myself.

You can also never know if there is a "professional spy" disguised as an amateur in the forum, but some members are declared professionals (Nelson Pass has shared with us so much of his knowledge, why not give something back if possible...).
But DIYers are in so many ways ahead of the audio industry, we can at least think in cost-no-object terms. And sound quality is a matter of taste and decision anyway ( ... thank you for offering your Krell, but keep it , I rather listen to my ZEN ... ).

I personally think that it should be allowed to discuss about "digital aplifiers", more because technology is constantly changing and audio is a subjective issue in general. There are new approaches by and others. I listened to some digital pro amps in the last years (LABGruppen, Sony, etc.) and they are not that bad, specially driving subwoofers extremly good. There are interesting approaches to switched power supplies (CHORD, LINN) which can sound very good (look how many studios use Chord amps now, they deliver the stuff we listen to after all). So this subject is HIGHLY discutable, in my opinion. Although I still listen mainly to "classical" classA and AB amps, which is not outdated in any sense, but I began experiments with new technology (powerOPs). Remember when digital consumer audio came up in the early eighties, it was just a joke, a ridiculous caricature. But now we all (most of all) are listening to digital sources, the development was breathtaking.
The technological difficulties in designing a "very good" classD amp are probably much more demanding. But so what. We all are not shy about "difficult" solutions. Is it by the way not a nice idea to have a high quality amp in pocket size, at least for your studio or workshop, while the big cooking class A monobloc is sitting in your living/listening room ?

I'm not sure that your point about CD technology is valid, as there's a world of difference in swinging 2V compared to, say, 30V with a great deal of current, and doing it cleanly. So far, commercial examples have been limited to low frequencies (e.g. subwoofer amplifiers), or pro sound applications, where the sound quality is of secondary importance at best.
Will the quality improve? I certainly hope so.
I don't see that my earlier comments qualify as prejudice against any technology, whether old or new. For what it's worth, I don't regard class D amplifiers as 'new.' The basic concept has been around for a while. If you're so quick to complain about the lack of 'new' technology, I suggest that you check the patent dates on some of Nelson Pass's work. Likewise Ralph Karsten (Atma-Sphere). I believe Krell has a patent (at least pending) on their CAST technology. Etc. etc. etc.
The tone of some of your posts leads me to believe that there is more than simple language difficulty at play, here. Just because no one picks up on your thread is no reason to complain, as you did in your second post above. If no one is interested at present--be patient. Someone may come along later and reply.
If someone is offering you a Krell and you don't want it, I'll take it. I can always use another channel or two of amplification...
On the subject of language:
I certainly try to make allowances for people who are not from English-speaking countries. When I was at the University of North Carolina, we had a lot of Asian and Oriental folks. I made a point of trying to understand what they meant, as opposed to what they were saying. It's good exercise for the brain. Besides, it's the polite thing to do.
I speak (or at least I learned in school) some French. I have since picked up a smattering of Spanish and Italian, and a few words in German and Russian.
I hope that I am never called upon to express myself in any of those languages, especially on any technical topic such as electronics. I'd probably end up requesting a massage from the milkman's car.
The thing that gets my goat is the lack of basic language skills evidenced by those whose native language <i>is</i> English. People from here (the US), the UK, Canada, Australia, etc. should possess at least rudimentary skills in their native language, yet are often left behind by those who are not from English-speaking countries.
It's pathetic.

digital amps


>I listened to some digital pro amps in the last years (LABGruppen, Sony, etc.)>

what models are you referring to??

class-d amplifiers are allready capable of giving very good sound quality so much of the challenging design work has allready been done :)

we have seen some pioneering work here in denmark (to my best knowledge lcaudio hasnt done much if any) and we demonstrate high-quality class-d amplifiers on a daily basis...

i think its also worth mentioning spectron class-d amplifiers, they have been around for some years and seem to sound pretty good too.

with the delicate design comprising hf , board layout , ground planes , emc and such it isnt best suited for diy im afraid though.

bye k madsen -
Dear K Madson,

I obviously also did not want to offend anybody.
I was mentioning from mind only, please do not ask me for special models. I was mentioning Lcaudio, because they have a new Digital amp on their intro page.
And you are right after a short survey I must admit that there are a lot approaches which seem to be technically mature.
But why did this approach not hit the market yet ?
Would it not be nice to have cool amplifiers (in both sense) with 100W in matchbox size ?

But, hey, why do I not remember the specific types first ? Was it because ...
No, they sounded quite OK.

Recently I listened to a relativly new digital amp SM-SX1 from Sharp (?) with a Sharp DX-SX1 SACD player and Wilson Audio Puppy/Watt loudspeakers (with expensive cables to be sure) - and yes, it sounded great !
I also listend to a system with big horn loudspeakers (from Advantgarde Acoustic) together with a digital amp (from TacT ?). The combination was not bad either, the importer told me that this amp likes the horn loudspeaker or vice versa. I can assure you, that I did expect that at least.

But after listening to many different amps - at a hifi show for Example - I always resume what I have heard and the classD amps never left a big mark in my memory.
Sorry, probably I am internally biased against these amps, I cannot help myself.
Maybe it is also because digital amps allow only a small amount of DIY approach ?

Can you please highlight the forum about your experiences and give (commercial and non-commercial) hints where to start ?
Do you develop the PWM Audio Technology ? Where can I listen to it ?

You have to be correct here, Arnach, and not mixing "apples and pears":

Spectral: is a already "classical" company making good solid state amplifiers. Trademark is the wide bandwidth (MHz !).
No digital amps, as far as I know.
Look at

Spectron: They produce very sofisticated professional digital amps, producing 1kW in 19inch/2HU or so.
Look at

I, however, must admit, that I do not like both brands too much. First one is somehow to "civilized" (clear, neutral, but a bit boring).
Second one cannot be considered as Hifi sound, at least the amp I have heard, I think it was the D1. But I only once attended a very dreadful demo. Maybe it was not the fault of the amp alone, but I had to go away quick. That maybe of no evidence, because I listened to very bad demos with approved good items (audionote and snell).
And many people consider this amps as the best digital amps available and rate them high.
I am not a believer yet, I am waiting for the first demo, which shows that this amps really like music more than watts...

But to provide lots of power with high efficiency is a viable task, so this amps fill a gap. Pop concerts tend to get louder every year...
Here's what I think about it all: I prefer the old class A, AB, and B(not so much B, they sould terrible). It would be a real shame if anyone came out with a digital amp so good that class AB amps started to become less popular. However, I think class T is very interesting, but most class D amps SUCK! BADLY! I think we should be open-minded to class T digital amps, and other good new technology that they may come up with. Many people swear up and down that tube amps sound better than solid state. I couldn't tell for sure, haven't heard enough tube amps. There will always be those that think the same about class AB as opposed to true digital. As far as CD players go, they don't have the full voltage swing that D's and T's have, so they're close enough to analog for me. Why do think they call part of the system a digital-to-ANALOG converter?
KiloWatt, in a digital amplifier there's also the part which converts the pwm signal into analogue, and it's not about which amplifier sounds good or better, it's the challenge to use another technology (and yes indeed class D is also quite old)
Btw, can you here the difference between a well designed PWM amplifier and a class AB ?
Also the demands on professional amplification it is not just about power, also about quality..
Anyway enjoy listening to whatever amplifier pleases you.
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