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In Reply to: RE: LOL... posted by dave slagle on August 18, 2016 at 06:56:32
again with the cherry picked set of conditions...
Class A is defined by conduction at max power. Cut off and it is an AB design. Could be deep AB, but is still AB.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Follow Ups:
What is max power in a linestage or other circuit than a power amplifier?
Plus at some point all class A circuits are going to cut off and I think the issue here is using a softly defined terms. (max power)
dave
"Plus at some point all class A circuits are going to cut off and I think the issue here is using a softly defined terms."
Part of the definition of Class A is how it's driven (loaded too, but that's a whole other discussion).
With Class A the input signal is limited to keep the operation within the linear part of the operating curve. That's just part of the package.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Where it printed that you must limit the input voltage in order to achieve Class A operation?
By extension of that concept, any amp you can clip is not a Class A design.
dave
It doesn't have to be printed, it's obvious.Tremaine page 604 "When operating as a single tube, class a, little distortion exists because the grid signal operates in the most linear portion of the dynamic characteristic."
With too much input signal the tube operation will go beyond the most linear portion of the dynamic characteristic [curve] and that little distortion will turn into a lot of distortion.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/18/16
I think the big difference here is between a general or first order definition being soft and ambiguous and a more precise model being the same.
The more precise the definition the less ambiguity allowed which is why we create more complex models in the first place and these models must be held to higher standards. Further defining anything with more imprecise terms is counterproductive and it is often these same people with complex definitions based on subjective terms espousing 5 decimal place accuracy to justify their opinions.
Tremaine uses the phrase "most linear" and while that seems like a strong statement, it is actually impossible to define without adding lots of other information / assumptions. Luckily his writings were directed to peers / students where a conceptual understanding of what he is saying doesn't take a huge leap of faith. Fast forward to today where on the interwebs, anyone can be an expert and we have a very different situation.
dave
Soft or ambiguous as it may be, I am quite comfortable ruling out any portion of an AB amp's power output as Class A. I am pretty sure the folks responsible for this were from somebody's marketing department...but given the target of such marketing should also bear some responsibility, I'll lay it on both groups.
For a linestage in particular, I would see no issue waiving the requirement for operation in the middle of the possible load line...could be the dose of 2HD available by running near cut off is desirable...LOL
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Where's the "most linear part" of this curve?
I think we have squeezed all the juice out of this orange. :-)
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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