How can "best" be applied to a wrong description?
The F5T with diodes is still a ClassA amplifier that transistions to ClassAB if the current demanded exceeds the ClassA limit. That ClassA limit is still two times the quiescent bias current.
The diodes simply allow a bit more rail voltage to appear at the output device Source leads, by reducing the volts drop across the Source resistors.
This is NOT more ClassA current. This is more output voltage capability at the same currents.
Some things only stretch so far
BTW, thanks for that signature reference. I would likely have missed that for months before I heard. Newport and Portsmith are across the bay from me now...
Why don't you guys fight it out. Problem for a big dummy like me is that there are numerous people on the forum with pretty gifted minds about this sort of thing. Every once in a while a topic comes up and there doesn't seem to be a consensus about what is actually happening. The proletariat get to watch as those who "know" disagree over what is happening. You may say this is a ridiculous notion, but here we are, year or more after the release, and there is still no consensus on how it works. Ridiculous, right. Go visit the Blowtorch thread if you need a specific example of how there can be disagreement by many different individuals that are extremely gifted.
Now I pose a question to you, Andrew, and it is honestly spoken out of ignorance(as if that had to be clarified). Why would Nelson relaese the f5T article with the claim of better drive of low Z loads, if all we gained was more voltage swing? ( not sure how this is helpful for low Z loads)If I need more voltage swing, I can just raise the rails on the standard F5. NO big deal. If it happens as you say, more Class A is just about more pairs and more bias.
Now I pose a question to you, Andrew, and it is honestly spoken out of ignorance(as if that had to be clarified). Why would Nelson relaese the f5T article with the claim of better drive of low Z loads, if all we gained was more voltage swing? ( not sure how this is helpful for low Z loads)If I need more voltage swing, I can just raise the rails on the standard F5. NO big deal. If it happens as you say, more Class A is just about more pairs and more bias.
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Pass is correct.
Demand more current and the output voltage drops due to increased loss through the amplifier.
There comes a point where your load demands so much current that the output voltage collapses. The load is too low for the current capability. That shortcoming becomes apparent by monitoring the output voltage at the demanded current being allowed to flow to the load.
Now look at what is happening around the Source resistor of an F5.
As the output load resistance decreases the Vdrop across the Source resistor increases. This is equivalent to saying that the output voltage drops.
We see this if we look at Maximum voltage into 16r0, 12r0, 8r0, 6r0, 4r0.
The Output can be specified as Power relative to Maximum into a high load mpedance (say 1k0 or 10k or ...), i.e.dBW ref max into 10k. It could also be specified as dBV ref max into 10k.
Some of the test reports use dBW and dBV and these reports make it very obvious when the manufacturer tells buyers lies about the suitable load impedances that can be driven.
Do this for a F5 with and without diodes and one will see the improved Vpk as low impedance goes down.
What Pass is saying is exactly the same as I described. There is improved Vpk (output) into the load and this becomes more pronounced as the load becomes more demanding.
Yes, we sometimes disagree, but usually it is a case of reading the wrong interpretation into what is posted rather than an actual disagreement about the science.
But we do need to learn what the diodes bring to the F5. There appears after a year that most still do not see it. It deserves more effort from the builders to understand what they are building.
Unfortunately too many builders want an easy life without any thinking and without any research.
Demand more current and the output voltage drops due to increased loss through the amplifier.
There comes a point where your load demands so much current that the output voltage collapses. The load is too low for the current capability. That shortcoming becomes apparent by monitoring the output voltage at the demanded current being allowed to flow to the load.
Now look at what is happening around the Source resistor of an F5.
As the output load resistance decreases the Vdrop across the Source resistor increases. This is equivalent to saying that the output voltage drops.
We see this if we look at Maximum voltage into 16r0, 12r0, 8r0, 6r0, 4r0.
The Output can be specified as Power relative to Maximum into a high load mpedance (say 1k0 or 10k or ...), i.e.dBW ref max into 10k. It could also be specified as dBV ref max into 10k.
Some of the test reports use dBW and dBV and these reports make it very obvious when the manufacturer tells buyers lies about the suitable load impedances that can be driven.
Do this for a F5 with and without diodes and one will see the improved Vpk as low impedance goes down.
What Pass is saying is exactly the same as I described. There is improved Vpk (output) into the load and this becomes more pronounced as the load becomes more demanding.
Yes, we sometimes disagree, but usually it is a case of reading the wrong interpretation into what is posted rather than an actual disagreement about the science.
But we do need to learn what the diodes bring to the F5. There appears after a year that most still do not see it. It deserves more effort from the builders to understand what they are building.
Unfortunately too many builders want an easy life without any thinking and without any research.
Typical you is answering question B, instead of responding to question A.
Likely, and as usual, because it's not in the book ?
Wasn't that basically all that you do, read books, and recite from them ?
Out of curiosity, how many times have you been asked to show something you did yourself over the years, instead of criticising others ?
Or, on just how many occasions have you asked others to measure something and post the results ?
Too lazy yourself, by chance, or so much to do and so little time ?
At the least, modesty is not exactly your most prominent feature, isn't it.
Your extremely bad manners and rather arrogant attitude are, as you've been told by some many others, over so many years, time and again.
And what do you actually amount to, If I may be so bold to inquire ?
A retired school teacher, with a civil engineering BSc ?
Posting on a forum 50 times a day, every single day, from 9 to 5.
To play the school whip, ridicule fresh members, to display your vast knowledge and experience.
The Mrs. doesn't allow you to play headmaster after 5PM ?
And provided you're not too busy, having to tend to the rose garden ?
Not exactly impressive, or is it, Mr TymkoWitz ?
At least I don't think so, rather pathetic is a more accurate description.
Main reason to have pressed the ignore button many years ago.
Just an exception, for your particular case.
Cheerio, Tata, Goodbye, and Fare Thee Well, laddy.
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I'm not sure were some people thought this was a "John Curl"(no offense John, just an example) but, it may have started here?
This statement is mostly true from what I've seen happening since publication. Not actually true however, the paper is only a suggested progression of the F5 design for the power hungry user. The actuall configuration can do whatever you want it to into whatever load you have, if designed properly.
Thank you FLG. I do not mind being wrong and if I am, I want to be corrected, but i like clarity in the correction. This is my understanding of how learning takes place. It is for this reason, I posted the example scenario in post #2212. Could you give an example of the differences in the above question.
Another example for sh^ts and giggles. I posted that my Altec 416's should yield 110dB with only 10w. I stated this because i used information obtained from the MJK worksheet in which th box was designed. It has been eluded to, that i am off in my thinking. Fine, but how? Are the MJK sheets wrong?
I am trying to understand and that type of thing is usually aided by those who do understand to the point of being able to explain.
Another example for sh^ts and giggles. I posted that my Altec 416's should yield 110dB with only 10w. I stated this because i used information obtained from the MJK worksheet in which th box was designed. It has been eluded to, that i am off in my thinking. Fine, but how? Are the MJK sheets wrong?
I am trying to understand and that type of thing is usually aided by those who do understand to the point of being able to explain.
Sounds good but I can't find the Buzzforb quote you are replying to. Is it that you edited something?
It has nothing to do with faster gates in a first approximation analysis. The 5A class A string is pretty much the same class A string (practically speaking). The 2X bias current classA rule is not modified very much by the additional diodes, if configured properly, at least the way I read the N.P. F5T paper. it is the classAB operation that you start seeing the rubber. Depending on implamentation of coarse. Rs's, Iq's, Vbe's, etc. When one side of the amp is practiclly not conducting and the other side follows the input signal to extreme currents (in AB mode) only allowed by the addtion of the diodes, that you will see this rubbery string thing. Rather than somewhat the opposite, current clamping, due to excessive source resistor losses.
Natuarrly the Voltages are a resultant issue but I preffer to think in terms of load current demand.
Where is my thinking flawed Jacco? Are we having a communication breakdown?
I thought the first part was fine but that last voltage perseption kinda deviated from my thinking??? It's not that its wrong but...
WTF Buzz? were you just in one of them threads were everyone takes shots at JC? so they can one up each other, do nothing but show there off thread intelegense etc. etc. etc. I don't think to many of us will allow that BS here from anyone. Go sit in the corner for a day! no Forum, no music!
Like I said, it is left up to the indavidual designer to configure thos ideas as they need. But you are right. I am of the low Z type...
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Absolutely nothing wrong with that statement. The rest,,, I'm more of a cuurent guy
Go read the article again if you don't understand this post! I don't know if he's right or wrong here