I could read, into their site, that operates class A and class B...and now they are saying AB is not good anymore!
It seems to me another automatic bias adjustment... some new dinamic bias adjustment.. from class A, going to AB and supressing bias into peaks of power.
Can someone explain how this works?
Thank you in advance by your kindness.
http://www.cambridgeaudio.com/summary.php?PID=292&Title=Azur+840A+(Version+2)+Class+XD+amplifier
regards,
Carlos
It seems to me another automatic bias adjustment... some new dinamic bias adjustment.. from class A, going to AB and supressing bias into peaks of power.
Can someone explain how this works?
Thank you in advance by your kindness.
http://www.cambridgeaudio.com/summary.php?PID=292&Title=Azur+840A+(Version+2)+Class+XD+amplifier
regards,
Carlos
Attachments
Thank you Sreten... i will read the white papers with attention
I hope the papers are low in level, to allow me to understand...two problems to read...my english and possible Engineering level explanations.
Thank you very much.
Also Rabbitz have bougth one of that, and i will listen what he will say about...also i have a nephew that will come to Brazil very soon, and i will buy one of them to listen to the XD operation.
regards,
Carlos
I hope the papers are low in level, to allow me to understand...two problems to read...my english and possible Engineering level explanations.
Thank you very much.
Also Rabbitz have bougth one of that, and i will listen what he will say about...also i have a nephew that will come to Brazil very soon, and i will buy one of them to listen to the XD operation.
regards,
Carlos
I really wish they would have come up with a better term than Class XD. It makes one think they are talking about some form of Class D, as in switching amplifiers. I think they used XD to mean crossover distortion. But they could have done something else. Lame choise on creating a new marketing class (like Class T and Class I).
I believe Douglas Self talks about this in his book (some of the graphs in the white paper looks like they were taken right out of the book).
-SL
I believe Douglas Self talks about this in his book (some of the graphs in the white paper looks like they were taken right out of the book).
-SL
I have readed the white papper with full understanding
A crossover point displacement system is the idea as i could understand.... XD as Extra Displacement, or axel X displacement is fine....not "class" in my point of view... this amplifier has not a class...not B, not AB and not A, as i could see.... will depend of the volume... a Variable Class Amplifier.
I remember Graham Maynard have made that with the GEM some years ago...and this was published...not too much different.
And the GEM i have built and sounded great.
The diferences obtained, into the distortion is something i cannot listen to something more difficult to listen.... i cannot listen both levels of distortion...smaller than Class AB distortion into good amplifiers that i cannot listen too.
Very interesting..i have to listen the sound to evaluate if i can perceive something.
Thank you folks...i am satisfied...now i will wait Rabbitz to make the review i have asked him and will ask Graham to explain to me the advantages or disadvantages this system has compared to his amplifier.
Doctor Self is usually very good.... now a days i am addicted to Doctor Self, despite he worries with some distortion i am unable to listen.....maybe other folks can listen.
regards.
Carlos
A crossover point displacement system is the idea as i could understand.... XD as Extra Displacement, or axel X displacement is fine....not "class" in my point of view... this amplifier has not a class...not B, not AB and not A, as i could see.... will depend of the volume... a Variable Class Amplifier.
I remember Graham Maynard have made that with the GEM some years ago...and this was published...not too much different.
And the GEM i have built and sounded great.
The diferences obtained, into the distortion is something i cannot listen to something more difficult to listen.... i cannot listen both levels of distortion...smaller than Class AB distortion into good amplifiers that i cannot listen too.
Very interesting..i have to listen the sound to evaluate if i can perceive something.
Thank you folks...i am satisfied...now i will wait Rabbitz to make the review i have asked him and will ask Graham to explain to me the advantages or disadvantages this system has compared to his amplifier.
Doctor Self is usually very good.... now a days i am addicted to Doctor Self, despite he worries with some distortion i am unable to listen.....maybe other folks can listen.
regards.
Carlos
Related my own personnal needs i am satisfied with the informations provided
by the white pappers....so... if you want to continue to discuss the subject go ahead... i will be out from the discussion because i think this is something i have to listen to evaluate by myself.
regards,
Carlos
by the white pappers....so... if you want to continue to discuss the subject go ahead... i will be out from the discussion because i think this is something i have to listen to evaluate by myself.
regards,
Carlos
Re: I have readed the white papper with full understanding
It's just marketing, Carlos. You could just as easily use CLASS DX. 🙂
..Todd
destroyer X said:
It's just marketing, Carlos. You could just as easily use CLASS DX. 🙂
..Todd
The notion of applying single-ended bias to the output of a power
amp has been around for quite a while. Take a look at the Aleph 0
from 1991.
Modulating that bias has also been done, but I found it much more
useful to modulate it against output current than voltage, as
it makes the effect independent of the reactance of the load. If you
modulate the SE bias by output voltage, it is optimum only for
resistive loads.
And while I'm at it, I think the technique of a SE current source on
the output is best used with a Class AB bias on the push-pull
portion of the output stage. If it is Class B, there is a significant
crossover distortion that is there unnecessarily.
amp has been around for quite a while. Take a look at the Aleph 0
from 1991.
Modulating that bias has also been done, but I found it much more
useful to modulate it against output current than voltage, as
it makes the effect independent of the reactance of the load. If you
modulate the SE bias by output voltage, it is optimum only for
resistive loads.
And while I'm at it, I think the technique of a SE current source on
the output is best used with a Class AB bias on the push-pull
portion of the output stage. If it is Class B, there is a significant
crossover distortion that is there unnecessarily.
Yes.... thank you the explanation..very usefull
Now a days i have a lot of FETs here.... will construct something from you Nelson.
The evolution of that one that you have used Lamps...nice amplifier that one...and them you made with CCS and other good ideas that made it more efficient.
Sorry, english continue awfull.
regards,
Carlos
Now a days i have a lot of FETs here.... will construct something from you Nelson.
The evolution of that one that you have used Lamps...nice amplifier that one...and them you made with CCS and other good ideas that made it more efficient.
Sorry, english continue awfull.
regards,
Carlos
My understanding is that it still operates in class A for lower levels and then goes into class B for higher levels. It just has the ability to stay in class A for a bit longer than a class AB with a hotted up bias.
I had a Yamaha A700 in the late 70's that was class A to 5W and then went into class AB after that. I have very fond memories of that amp and there's no denying that class A sound is very appealing. Better than any Yamaha I've heard since.
I have some fine DIY amps, AKSA55N & N+ plus a LF55, but due to a deteriorating medical condition I needed something with more convenience, flexibility and widgets for the future so I looked for something with a high bang for buck and was within my budget, hence the Cambridge Audio 840A V2. I have a 840C CD player so a good match.... I hope.
I think the class is irrelavent as it's the final sound that matters plus there are great examples from them all. It will be interesting to see if it's as good as my DIY amps. If it comes close I'll be very happy and if not, I'm prepared to lose some SQ but will have the ability to be able to use it.
So far the sound is very promising as it's been set up in my office to burn in. Listening to some nearfield speakers, a very smooooooth detailed operator so far..... 30 hours more and into the main system.
I had a Yamaha A700 in the late 70's that was class A to 5W and then went into class AB after that. I have very fond memories of that amp and there's no denying that class A sound is very appealing. Better than any Yamaha I've heard since.
I have some fine DIY amps, AKSA55N & N+ plus a LF55, but due to a deteriorating medical condition I needed something with more convenience, flexibility and widgets for the future so I looked for something with a high bang for buck and was within my budget, hence the Cambridge Audio 840A V2. I have a 840C CD player so a good match.... I hope.
I think the class is irrelavent as it's the final sound that matters plus there are great examples from them all. It will be interesting to see if it's as good as my DIY amps. If it comes close I'll be very happy and if not, I'm prepared to lose some SQ but will have the ability to be able to use it.
So far the sound is very promising as it's been set up in my office to burn in. Listening to some nearfield speakers, a very smooooooth detailed operator so far..... 30 hours more and into the main system.
I have downloaded the Brochure and i have to tell you i am crazy to buy one unit
alike yours.
I want to know the price, for the complete line....if you have this information, please, go to my mail.
Thank you Rabbitz.
regards,
Carlos
alike yours.
I want to know the price, for the complete line....if you have this information, please, go to my mail.
Thank you Rabbitz.
regards,
Carlos
I too have wondered about the Cambridge "XD" Is this one of Doug Selfs designs he did for them. It would be fascinating to see a circuit of it. Doug always championed Class B as being able to provide better distortion performance than all other classes apart from Class A. Is this still a valid view do think ? The evidence at the time was compelling in particular the distortion and gain plots.
Just going slightly off the topic but related to biasing, has anyone any experience of, or seen a technique of biasing HEXFETS using an optical bias system that maintains the optimum point under all conditions, as opposed to a vbe multiplier.
All very interesting,
Karl
Just going slightly off the topic but related to biasing, has anyone any experience of, or seen a technique of biasing HEXFETS using an optical bias system that maintains the optimum point under all conditions, as opposed to a vbe multiplier.
All very interesting,
Karl
I just cannot wait to have this unit schematic into my hands
Do not know how i will get that...but i am lucky and this schematic will appear into my mail adress and very soon.
I just cannot stop to think about....my God!... i am sick for amplifiers!....if i had the chance to watch the schematic, in a couple of hours i will assemble and will be listening at it and will make noises here into the forum.
Of course will not show schematic if secret..but will listen..for sure will listen to it...for sure!
I am scratching my head...my God...nephew will come in December...too many monthes.... do not know if my heart will resist to that.
MAN!... I HAVE TO LISTEN THAT!!!
HELP!!!
Carlos
Do not know how i will get that...but i am lucky and this schematic will appear into my mail adress and very soon.
I just cannot stop to think about....my God!... i am sick for amplifiers!....if i had the chance to watch the schematic, in a couple of hours i will assemble and will be listening at it and will make noises here into the forum.
Of course will not show schematic if secret..but will listen..for sure will listen to it...for sure!
I am scratching my head...my God...nephew will come in December...too many monthes.... do not know if my heart will resist to that.
MAN!... I HAVE TO LISTEN THAT!!!
HELP!!!
Carlos
Attachments
Nelson Pass said:
Hi,
The old chestnut. Class B and class AB - what are they.
I prefer class B = no bias, class aB = optimum bias, class AB overbiased.
D.Self refers to aB as B. For the XD technique his class AB is not useful.
🙂/sreten.
Hi Richard,
Interesting reading (how did you turn that up), in effect at first glance, it looks just like we have been doing for years, sinking curent into an OpAmp output stage to shift the non linear crossover region away from the zero point, although the the XD seems to elaborate on this by talking of modulating the current sink.
Interesting reading (how did you turn that up), in effect at first glance, it looks just like we have been doing for years, sinking curent into an OpAmp output stage to shift the non linear crossover region away from the zero point, although the the XD seems to elaborate on this by talking of modulating the current sink.
Gotta love marketing classes causing confusing. Let's make a new Class to make people think 'This is totally new, never done before, greatest invention ever' when all of them are just some modification of an existing and well known amplifier class (or technique). I can never understand why Self refers to it as Class B when it is so much better known as Class AB. Makes much more sense to have A, B and then AB as a combination of A & B trying to get the best of both while avoiding the worst of each.
-SL
-SL
Hi Sreten,
---class B = no bias, class aB = optimum bias, class AB overbiased.---
Self has written an article called, I think, "Class distinctions" published in Electronics World. The aim of his classification is to avoid confusion.
I retained from that :
As no bias could also be class C, Self prefers to call class B an amplifier having at any time, at least, one of the branches of the output push-pull conducting.
He then introduces sub-classes, A+B, A+C etc.... to more precisely describe the biasing.
---class B = no bias, class aB = optimum bias, class AB overbiased.---
Self has written an article called, I think, "Class distinctions" published in Electronics World. The aim of his classification is to avoid confusion.
I retained from that :
As no bias could also be class C, Self prefers to call class B an amplifier having at any time, at least, one of the branches of the output push-pull conducting.
He then introduces sub-classes, A+B, A+C etc.... to more precisely describe the biasing.
To tell ya the truth guys, i feel very confused about those things
In my mind, class B means the transistors are not conducting...cutted.... can have some bias, but smaller then the threshold that will put the transistor into conduction...lets say... 400 milivolts for instance.... the audio will bias the circuit and will put it into conduction.... this is in my mind...help me and correct if i am wrong.
In my mind, class AB means small quiescent current, small stand by current, all transistors in conduction... from base to emitter the voltage will be small... from 500 to 600 milivolts... very distant from saturation... and amplifiers of 50 to 100 watts use to have stand by current from 30 to 100 miliamperes.... smaller power use normally lower stand by current and big amplifier with many output transistors use higher stand by current...that can reach 250 miliamperes.
And Class A when you force the transistors into Huge conduction, voltage from base to emitter is advanced related 600 milivolts and some transistors are midway between cut and saturation.
Well... the frontier, the border, the limits between Class AB and Class A is confused to me.
If you wanna help me to remove my feet from the lame of ignorance, please explain me other way to understand all that stuff.
regards,
Carlos
In my mind, class B means the transistors are not conducting...cutted.... can have some bias, but smaller then the threshold that will put the transistor into conduction...lets say... 400 milivolts for instance.... the audio will bias the circuit and will put it into conduction.... this is in my mind...help me and correct if i am wrong.
In my mind, class AB means small quiescent current, small stand by current, all transistors in conduction... from base to emitter the voltage will be small... from 500 to 600 milivolts... very distant from saturation... and amplifiers of 50 to 100 watts use to have stand by current from 30 to 100 miliamperes.... smaller power use normally lower stand by current and big amplifier with many output transistors use higher stand by current...that can reach 250 miliamperes.
And Class A when you force the transistors into Huge conduction, voltage from base to emitter is advanced related 600 milivolts and some transistors are midway between cut and saturation.
Well... the frontier, the border, the limits between Class AB and Class A is confused to me.
If you wanna help me to remove my feet from the lame of ignorance, please explain me other way to understand all that stuff.
regards,
Carlos
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