Howdo these new class D amps compare?

I know that class D is a newer amp topology and that it is getting better every day but I am curious how the new low distortion versions are comparing to Current class A designs. The amps I have in mind are along the lines of the Aleph, leach, and JLH. These amps have been around and all are well known as quality amps. So how do the new kids on the block stack up?
 
Class A / class D

mastertech said:
class-d as is digital is a translated form of audio when you compare this with true Analogue and its classes a,b,ab where
the original signal is processed as is you can see why hifi revolves
around them

digital and class-d are nice but not hifi

cheers

Class A can be very nice at low volume/power but still is hopelessly old fashioned sounding like a 50's radio. It has extreme coloration and distortion above a couple of watts. It is totally at the mercy of all the parts that make it up and each one contributes to this coloration. I am not saying this can't be very pleasant, at least for a while but who wants syrup on every thing? The job the output transformers have to do makes them very expensive, large and limited in bandwidth. The class A claim to fame is the old “first watt” thing. This relates to letting through the low level information so is very noise dependant. Typical class A has high noise and low power meaning very restricted dynamics. The typical solution is to by a set of very efficient speakers that introduce even more coloration. WOW, now we are back to the 40’s!
If you want the state of the art regardless of cost, the best of the class D amps are your only choice.
The reasons are many as they are;
The very best at reproducing low level information without compression or distortion,
Very low in dynamic compression at all playback levels,
Very low in distortion at all levels and frequencies,
Very low in noise in the audio band,
Have no crossover or hysteresis distortion masking low level information,
(Any hysteresis distortion due to the output filter occurs at the peaks of the switching waveform and doesn’t interfere with the signal.)
Extremely low in coloration from parts that are within the feedback loop,
Extremely high in efficiency,
Have very little or no sonic penalty for higher power,
Have excellent rejection of power supply noise.
Have a real rightness about reproducing the leading and trailing edges of all sounds,
Have exemplary sound staging when coupled to an adequate power supply,
Their life expectancy is many years including obsolescence with no or very little maintenance required,
And last but far from least one of the modules will not cost as much as a single quality output tube. A really nice whole amp can be built for the price of a couple of quality class A output transformers.
Convinced yet? There is much more that I haven’t gone into!
You came to the wrong place to say that class D is not hi fi. But I guess it isn't if your reference is a 50's radio sound.
Roger
 

classd4sure

Disabled Account
2004-02-13 3:35 pm
www.diyaudio.com
class-d as is digital is a translated form of audio when you compare this with true Analogue and its classes a,b,ab where
etc


Hi,

If class D is digital than so must be class B and AB? Really to me your post seems like a fishing expedition, why don't you do some research on the subject yourself and you'll sound better informed.

There's veery little, actually nothing I can agree with on what you've posted.

I have my doubts you've even heard a class D amplifier, and are amongst those still thinking it's for bass only.

I also agree with Roger and class A coloration, theoretically both class a and d are 100% linear, in reality a good class d probably outperforms a good class A, certainly it leaves it in the dust as it maintains performance over 10X the power band even possible with class A.

Mastertech, sell tube amps, do you? :)

Regards,
Chris
 
The opinion from someone who says that Class-D means "digital" seems of little weight and validity to me. One cannot post such categoric affirmations without knowing what he is talking about.

For an easy and very light introduction to Class-D, please have a look at this article. I think it is quite educational and I hope it helps changing everyone's mind about this new and excitant technology, without hiding its difficulties.

http://sound.westhost.com/articles/pwm.htm
 
ssanmor said:
The opinion from someone who says that Class-D means "digital" seems of little weight and validity to me. One cannot post such categoric affirmations without knowing what he is talking about.

For an easy and very light introduction to Class-D, please have a look at this article. I think it is quite educational and I hope it helps changing everyone's mind about this new and excitant technology, without hiding its difficulties.

http://sound.westhost.com/articles/pwm.htm

The most difficult thing about class D is deciding whether to buy Lar's design or Bruno's. From there it is straight forward implementation. Really, doing a class D design from scratch is nonproductive from a time and money standpoint unless you are doing something really different, unfortunately, then your chance of success drops even further. I consider myself a competent analog designer and have done some interesting and complex things but I know enough to realize how long it would take to get up to speed on this technology. And, I have to ask myself what would be the point in trying to do something that worked better than the 2 products mentioned. I am not saying there is no room for improvement as there is but by the time I got to that point they would be 2 years ahead of me. I am sure there will be more competent class D designers in the future as most of the fundamentals are now done and can be taught. Of course this will be a class in analog design, not digital and I am not sure how many students will be attracted.
Roger
 
mastertech said:
class-d as is digital is a translated form of audio when you compare this with true Analogue and its classes a,b,ab where
the original signal is processed as is you can see why hifi revolves
around them

digital and class-d are nice but not hifi

cheers


No, they are for sure not hifi, they are High-End.

And most of them are true analog as well and can easily beat many so-called high-end conventional amps. If you have heard a good class D amp, I`m pretty sure you don`t want to go back to conventional anymore.

Try it and find out.

Gertjan
 

t.

Member
2003-05-26 1:35 am
notts
You do have to keep an open mind with this new technology.
I've had a diy tube amp for a few years now, the stone each in weight output transformers alone cost more than a pair of the UCD400 modules, the sound is far from syrupy and measures extremely flat.
I've built and listened to various solid state amps and wasn't really blown away by any, yes a lot of tube amps do sound bad too;)
I also read bad things about class-D but decided to buy one of 41hZ Audio Amp3 kits to try out seeing as though it cost peanuts and should give me an idea how this new technology sounds.
To be honest I was amazed at the sound that came out of this tiny amp, it would put a lot of expensive solid state amps I've heard to shame.
My speakers could do with a bit more juice than what the Amp3 can give so I'm getting the parts together to build a pair of UCD400 amps:) at least these things run nice and cool unlike tubes:D
 
"Digital and Class D are nice, but not hi fi."

This sounds like a statement made by someone who has never heard this implementation. A very well implemented single ended Tripath TA2024 based amp, same as the one in the legendary Sonic Impact, a $20 plastic amp, can provide a sound where many listeners prefer that signature to VERY high dollar single ended tube sound. I know, because I did exactly this experiment in my home, with my equipment.

Class D, such as it is called has become a very narrow-seeming term. It is the way of the future.

"Ignorance hath the loudest opinion." --Robert Burns
 
Well, for once, I decided not to say what I had on my mind. Someone here should consider themsleves lucky.

Today.

The Class D stuff from years ago was rather nasty sounding, but with the newer generation, that is no longer the case. Still, it does sound different, and different enough to put off some people.

None of the people who design the technology on question call it "digital". They all hate that term. The amps are linear devices that essentially control a SMPS. All amps are nothing more than modualted power supplies. These just happen to have switching suppies.

Usually fed from a good ol' transformer/filter cap combo.

I don't agree that Class A has to sound syrupy. Power hungery, yes. Which is why mine are all turned off now.


Jocko
 
Hi Jocko,

I wouldn't say class A has to sound syropy either, but I think the only point it was worth bringing up for was to simply to say that while on paper they're both ideal, in reality...

Therefore I don't find it a valide argument to hold over class D. They both have their problem areas, I think it's much more feasible to overcome most limitations with class D however.

I do agree with mastertech, all class-d's that I've heard do share similar characteristics, lots of air, lots of dynamics, lots of detail... I'd never call that digital, I really like it, and sure a sonic impact would be a good way to find out, but if you had to pick 1 class A amp to stand for all the rest..... would you be content with it being a 20$ chip amp?

Regards,
Chris
 
Common characteristics of class D sound

What is it about class d that gives this sonic effect, if it is an effect at all? I think it relates back to the physical properties of all conductors that are crystalline in nature. When an electrical signal crosses the gap from one crystal to another it takes a certain amount of energy to do so. This energy is then lost from the original signal. Think about how much more information comes across a really good set of monocrystalline cables. It also explains why there is such a thing as break-in. This could be the process of these crystals welding them self’s together. All this relates to low level information transmission. We would be more sensitive to the high frequency aspect of it because the treble contains less energy and the loss percentage would be greater.
Could it be the high frequency residual and in fact the main power switching solidly bridges these energy gaps allowing the low level stuff to get through where before it was lost? In careful listening to both d and a/b amps it does seem to me to be this kind of difference we are perceiving. If all this is true this would separate the d amps from all the rest and I think that is just what is happening!
Now if you really get to thinking about this it answers a lot of questions about different sounding stuff and what makes them different, of course disregarding all the readily measurable stuff. Maybe all we need to do is turn down our THD test signals to really low levels to get a more accurate correlation with what we hear. This could be important!
Roger
 
Thanks for the responses but it seems mastertech kinda bumped this post in a different direction then I ment it to go. I am more intrested on how the amps like the zappulse line (ie. 700xe) and the UcD line against other quality DIY amps such as the ones I posted before. I really don't think it makes much sense arguing about classes.

I don't want to get off track but classd4sure when you say "class A coloration" are you refering to tube amps. If so I understand that statement due to the fact that there are a a lot of poorly designed tube amps around. If you are talking about SS class A amps could you explain more of what you are talking about?
 
DJNUBZ said:
Thanks for the responses but it seems mastertech kinda bumped this post in a different direction then I ment it to go. I am more intrested on how the amps like the zappulse line (ie. 700xe) and the UcD line against other quality DIY amps such as the ones I posted before. I really don't think it makes much sense arguing about classes.

I don't want to get off track but classd4sure when you say "class A coloration" are you refering to tube amps. If so I understand that statement due to the fact that there are a a lot of poorly designed tube amps around. If you are talking about SS class A amps could you explain more of what you are talking about?

Hi,

I think you're question is best answered by just looking at the specs of the different amps, keeping in mind what you expect from an amp. Yes THD is implied when I say that but that hardly scratches the surface of what you should be looking at.

I think in the end the result will clearly show high end class d amps have a definitive edge over the rest as it simply gives you alot more of what most people want and enjoy in an amplifier, and alot less of what you don't want, namely cost per watt and power loss, assuming equal quality, which I don't believe it is, I prefer class d for it's sonics without question.

Roger, while I personally would not be so ready to start discussing the mono crystal theory, I will certainly agree that class d has an edge in that it modulates instead of amplifies, thereby largely doing away with most of the individual components influences. You have to have a good modulator and treat that like an analog system, since it is one.

Think about the slew rate between a switching amp and any other for instance... perfect example.

Now when I said class A coloration I was paraphrasing what I believe was the context of a previous post. In that I meant any class A and coloration by be it your mono crystral theory or the usual delays, bandwidths, parasitics, etc.

We still have all those to deal with in a class d amp design but they can and do get dealt with in such a way that they're no longer the controlling factors in the audio that results, exactly because they operate in switch mode.

That's not to say each component doesn't have it's influence on the sound either, certainly the passives.

No easy answers.
Regards,
Chris
 

KLe

Banned
2005-07-15 1:26 am
Brisbane
Hi DJNUBZ: IMHO, I think that you will find the Zappulse 700XE to be a very fine amp. I am currently using the Zappulse 2.3SE, which after tuning, is a very good amp and I believe that the 700XE will be better (at least Lars and listening testers say that it is?). ;)

I have found that the sound of the Zappulse 2.3SE is dependant on the quality of the PS. Eg. 1KVA tranny is better then a 500VA tranny, short wire connections to the PS Caps is important, 0.22uF caps controlling zener diode noise is critical, etc? :bigeyes:

I cannot comment on the UCD amps, but wrsto UCD amps, I am sure that someone will be able to provide you with a summary :att'n:
 
dmason said:
"Digital and Class D are nice, but not hi fi."

This sounds like a statement made by someone who has never heard this implementation. A very well implemented single ended Tripath TA2024 based amp, same as the one in the legendary .....

"Ignorance hath the loudest opinion." --Robert Burns

This sounds like a statement made by someone who has never read a spec sheet, understood a schematic, or has a clue as to topology, yet nevertheless spouts technobabble, feeling that such throwaway descriptiors as 'single ended' to describe the TA2024 gives their opinions credence.

In which alternate universe would the bridge tied load TA2024 be considered single ended? I've no problem with your sharing your opinion that you find your Red Wine amp preferable to your previout SET amp, but please spare us the nonsense.

"Ignorance hath the loudest opinion." --Robert Burns