I have found a special amplifier, am trying to contact the designer

[AndrewT]

Hi Aksa,
Posts 36 & 39 asked questions about ClassA currents.
I answered with the conventional definition.
You came back in post 43 with an unconventional definition, with which I do not agree.
Now, what's up?
Is Steve or Wavebourn or you prepared to offer more unconventional definitions of ClassA or are we going to enter into the realm of modulated ClassA bias and whether it does or does sound as good as real ClassA?
There are two modulated single ended ClassA that I'm aware of that can sound very good, namely JLH & Pass. Maybe Steve's is a third contender.

But the basic question remains: Does ClassA require big bias curents?
I and many others say YES.

 

[AKSA]

Andrew,

Let's clear this up once and for all.

I did not question your definition. It is both textbook and correct. Neither did I intimate otherwise, or convey negativity in any sense. A textbook opinion is fundamental, and worthy and an excellent start point for those that think about the basic phenomenon.

I simply asked that we return to basics, and consider what happens as one device switches off, and hands over to the other.

I pointed out that if the inactive side could always remain on, then one important source of HF artefacts would no longer be injected into the speaker line. This is one very important source of HF distortion in push pull Class AB amplifiers, as you know.

You replied with this:

if this modulated trickery is what Steve and/or Wave are referring to then it's not ClassA.

Actually, I said it was Class AB doing Class A tricks. Please get it right. I would not regard it as anything more than quasi-Class A, and certainly would not waste my energy on semantics.

I enjoin this forum for stimulation and group debate, not to be chastly reminded of turning to page 123 of the textbook. You seem keen to school everyone, and correct their mistakes like a wise schoolmaster!

If you take this approach, expect occasionally to meet people who challenge and who do not take kindly to being so treated.

You further went on to stigmatise this approach, and generally deride the efforts of people far smarter than you and I put together, people such as Nelson Pass who have expended a great deal of intellectual energy in the careful analysis of such 'bastardised trickery', as you put it.

Remember, Andrew, that progress only comes from those who step outside the textbooks - men like Nelson.

Now wake up to yourself and stop being a thought policeman. If you comment, please add constructively to the debate. My intention was, and remains, as you flagged - maybe Steve has another. Let's wait until he responds, OK?

I make comment only on your reply, not on your personality. Texas is much too hot for me.

Hugh

 

[kASD]

Andrew,

I dont think that definition of Sliding Bias Class-A is unconventional, because in both the definitions the main thing to consider is that the device never TURNS-OFF. Whether you do it with forcing high bias current or choose sliding bias...........aspects associated with it wont change. Its just what we call thinking outside of the box.

You seem keen to school everyone, and correct their mistakes like a wise schoolmaster!

Andrew is a teacher, ofcourse
but sorry we are not his students.

 

[Iyremenko]

Andrew, you are sounding like typical bookworm fundamentalist who always stick to what is written in a pack of papers, but at the sametime fails to understand that the mind working behind it has certainly no limits. All definitions of Class-A are acceptable as long as the device doesnot switches OFF.

I fully agree with AKSA and Workhorse.

 

[destroyer X]

Fundamentalist is hard, despite i can agree...the problem is if not fundamentalist...

others, alike us, diferent ones..will be unfidel.

http://www.youtube.com/watch?v=1uwOL4rB-go

Well guys..... Dunlap may come to clarify....maybe.

I would be afraigthned in his place.

Well... we will be here to help him.

regards,

Carlos

..................................................................................................

Iyremenko and Hugh

I am glad to see others have perceived something about that.

I was starting to think i was not a tollerant guy... i use to complain about that and i felt i was alone thinking this way.

thank you,

Carlos

 

[Mooly]

Seems to me the conventional and long established definitions are no longer capable of fully covering all the different schemes on offer.
I have been brought up on the old definitions and can't really accept sliding bias and gated bias schemes as pure Class A as I understand the definition.
No ones right or wrong though.

What I do find misleading are specs such as in post #24
Here we have what is described as a 1400watt/4 ohm amp with a current consumption of 230 watts. Is that at idle ?
The established definitions do not cover these designs.

Can I ask a question ? In the US and places on 110 volts, how much current can you draw from a single outlet ? In the UK it's 13 amps nominally.

 

[east electronics]

HMMMMMM

Carlos, why don't you get more involved into speaker building? They are the biggest limiting factor in sound reproduction.

ONCE i had in my shop a 3 way speker box emty

then i add to the emty box a tonsil tweeter dome type gdc11/100

then i had a couple of visaton woofers i think about 45w each .....

had no midrange but i had a pair of simsonic car speakers mady of blue vinul and a silver cone so i thought they will look cool built a housing arround them to use as midrange ....

put the all thing together and start to work with the xover which i actually copy the way JBL TLX 20 series is working with a few changes to match the digferent units ( i liked so much the idea of bypassing the big capacitors with 100-220nf that exist in TLX series)

this all resulted to a speaker that i ve never heard before so nice and sweet compaired to many comercial regarding quality

only negative is that there is a small gap between mid and high ..... but very very smal

 

[The golden mean]

Quote "You further went on to stigmatise this approach, and generally deride the efforts of people far smarter than you and I put together, people such as Nelson Pass who have expended a great deal of intellectual energy in the careful analysis of such 'bastardised trickery', as you put it."

May I suggest that we give up any attempt to evaluate or determine who is the smartest guy on this forum? If we stick to a discussion on subjects rather than people´s traits or personality I hope we can have some peaceful discussions for a long time...


Best regards

Håkan

 

[AndrewT]

All definitions of Class-A are acceptable as long as the device does not switches OFF.

I fully agree with AKSA and Workhorse.

That's precisely where we disagree.

 

[destroyer X]

Yes Sakis... will delay a lot to them to forgive or forget

What i have said about class A..... now i am not kind anymore, not wise anymore, my amplifiers are not good anymore, i am not skilled anymore.... .... no... i do not regret...but reaction was bigger than i was hopping for...some folks thinks they are Class A inventors and felt offended inside their intimate feelings.... there's a confusion.... they think if i said class A not perfect ... this means they are not perfect too.... and i think class A is just an amplifier class, not humans, not souls or honors!

Sacrilege! .... shocking thing I have told them… we cannot talk things against established beliefs, the traditional ....some friends turns angry and reacts with energy, with force, with great intensity… and as usual, keeping forum rules untouched… the reality is that they want me to hook myself with my crazy ideas ... and I have said what I think is really subjective, personal, that suffocation… the muffled sound is a small effect (not really a defect) and can be fixed using a tone control, you know, fixed to my taste, as I ever have perceived that..but audiogram examinations told I am not deaf..so I felt I could be rigth about that and made my comments to be true with forum folks. Just to turn treble to 3 hours, clockwise, increasing it a little..and everything turns fine to my “wrong” speaker..my “wrong” home acoustics and “wrong” perception. They will never forgive me because to tell those things..in special if they have those heaters inside home…they will attack my speakers, my equipment, my wife, my dog ... will say that I am deaf,they will put doubts about how wise I am, how skilled I am… will think on me alike a menthal retarded man, stupid, ignorant, lunatic and will desperatelly reduce the importance of everything I have told till the moment I have attacked the stablishment with different ideas.

And i have said some class A may sound not mufled.... that i was searching for those units... and i have found something to assemble, to listen, to test, to check those thougths.

Even this way people will say my speakers are made of paper.

hehehehe.

regards,

Carlos

 

[homemodder]

The amp in post 24 is not a class A amp, it will maybe give 20 watts in class A, 230W is at dle, Comsumption is high at idle because the drivers of this amp are biased at high current and never leave class A opearation. Nothing misleading about it, remember the magazine writers are usually not technically electronics trained and just copy some specs from the manuals and even then they get it wrong because they leave out crucial information.

 

[destroyer X]

Yep Homemodder.... you are rigth...but even if people found you wrong

They would say "it is not a real Class A.!".... this gonna be told by class A addicted.

The non addicted folks will say it is not a Class A..."it is just a higher biased class AB"

ahahahhaha!.... não tem saída amigo...o ditado Luso Brasileiro se aplica aqui:

- " Se correr o bicho pega!... se ficar o bicho come! "

No chance...if you stand without move, the monster will bite you...if you run the monster will run behing you and will bite you either.... anyway, despite all you can do, they are really biased into class A...highly biased, and will always run behind you to bite you.

No problems, to me this is "fun"... i do not mind about...it is all rigth...i am still happy.

regards,

Carlos

 

[MJL21193]

Re: MJL21193..... this nice barbecue you are showing seems that had suggar applied to it

So.... to me my barbecue is better..for you your barbecue is better.

But i think your barbecue is pretty, this colour is very nice.

Also i do not like it bloody.... i love it roasted outside and rose inside.

Those things are very personnel...connected to our local culture.

Enjoy your barbecue my Transistorized friend.

Thanks Carlos,
Those are ribs, from the pig.
Steaks I don't put any sauce on, just salt and black pepper. Cooked medium rare (bloody!).

Good luck with your search for the perfect amp and the perfect BBQ.

 

[destroyer X]

Yep.... Costeletas de Porco.... i understood and i could see them

Made me feel hungry...hummmmmm...nice those things...even with sugar.

Yeeeessss!

And they are inside our souls...we do that since the stone age...this belongs to us...around the fire, with our friends..good the meat delay...we can be hours talking foolishes and eating good meat.

Mooly will dislike..but i love cow meat.

regards,

Carlos

 

[destroyer X]

Well Mr. Steve Dunlap... the bias is a little bit polemic

I am deeply interested to assemble and to listen by myself, to evaluate by myself at my home, and to compare with the units i have here.

I am not really biased...if better than my units i will tell you without any problems... i have found others better than my ones...but as i use to say...not too much....mine toys are not ashamed by anyone.

So, schematic please...if do not want to feed polemic in this moment, please, send it to me, and when forum turns calm we can go ahead.

It is interesting...people is interested.... the subject is really polemic, we will never make Greek and Trojan happy.... or one or other...both same time is hard.

This is a say here...hard to make Greek and Trojan happy at same time...almost impossible.

regards,

Carlos

...................................................................................................

Were is Thomas...i am perceiving him not into the forum but tuned on us ..... were is him?

regards,

Carlos

 

[darian]

Just an opinion

Hello,

Just a point of view about the minimum residual bias trick and what it does compared to true class A :

Class A compared to class AB or B avoids 3 distortion phenomenons which are 1) crossover distortion 2) switching distortion 3) Gm doubling.
I think everyone agrees on that at least.

So when we use this minimum bias trick to keep the output devices always on what happens? Let's see :

1) Crossover distortion is reduced, more and more if the residual bias is high. Typically there is some left. It's the most annoying type of distortion.

2) Switching distortion is suppressed, but in a normal topology an adequate reverse biasing by the drivers can make it unmeasurable too.

3) Gm doubling is still present, with a more abrupt transition from one state to the other since the gain of the device disappears when the brickwall of the minimum bias is met. In normal operation the transition is smoother.

So to me, it's really not an equivalent of class A but it has some clearly interesting features. I think the best way to define TRUE class A is that the devices stay ON and STILL AMPLIFY so you can really eliminate all the distortion types, including Gm doubling.
With JLH or PASS, it's clearly high bias class A, with a quasi-complementary approach and different amplification factors for the 2 sides of the push-pull.

Regards

 

[lumanauw]

There are some definition of "non turn off" output stage. Some say never turn off (every output transistor has a certain bias current flowing all the time) is enough. Many patents like from Japan are about this.

But some give "harder" requirement, that is the continuity of Gm. In classA, Gm is relatively constant even in handover (crossover) around 0V from PNP to NPN vice versa. In lower than classA bias, there will be dip or valley for Gm curve around 0V. Douglas Self book shows these graphs.

Many "Non turn off" output stage cannot fit into this 2nd criterion, even all output stage transistors never turn off.

 

[analog_sa]

Hi analog Im an ex SA, joburger.


Muffled, these?????? HaHaHaHaHa................

The "Mufled" joke was refering to another anti-classA thread of Carlos. I have listened to the AW180 and liked it a lot. Did you leave SA around '88?

 

[AndrewT]

I am so glad that the books of wisdom that some here revile have a bit of support from the enlightened.

I would hate to throw away all the books and with it all the rules and start afresh with some of the ideas I see expounded.

Or to put it another way, the rules governing ClassA do not change because new and improved topologies are invented.

 

[east electronics]

O !!!!! Come On Guys

CONSTRUCT SOME AMPLIFIERS .....

BOOKS AND THEORY IS WERE ALL STARTS BUT DOESNT GET FINISHED UNTILL CONSTRUCTED !!!!!!!!!!!!!!!!!!!!!

does it realy makes so much sense if its called this or that ?????

the important is to study look construct listen improove if possible or improove to your own taste and go on .....

lets see some construction talk !!!!!!!!!!!!!!!!!