"In the class AB there is a portion of the signal where the circuit is in class A , proportioned with the bias current and,of course , with the load."
Cattle, exhaust, solid type, un-neutered male origin.
Class A conducts all the way to full power. AB conducts 360 degrees at low power only. The starting point is also a property of A...AB starts colder than an A point. Class B is not 180 degree conduction; there is some overlap. It is not Class A whilst it is happening...it is B. Amps don't change class... 🙂
Douglas
Cattle, exhaust, solid type, un-neutered male origin.
Class A conducts all the way to full power. AB conducts 360 degrees at low power only. The starting point is also a property of A...AB starts colder than an A point. Class B is not 180 degree conduction; there is some overlap. It is not Class A whilst it is happening...it is B. Amps don't change class... 🙂
Douglas
That's class A operation. ...in your AB amp. Call your amp what you want but 360 degree conduction of both tubes at the same time is PP class A operation. The opertional condition is its own definition apart from the label for your amp.
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I wrote portion, maybe is better "level"
And in class A if not well dimensioned, with a real load it can switch to AB
And, also, when well dimensioned an AB amp with fixed bias, you can reach a good power ( increasing the bias current) in class A.
Then, I wrote
"Otherwise is class B, near the cutoff"
I never said 180 °
Walter
And in class A if not well dimensioned, with a real load it can switch to AB
And, also, when well dimensioned an AB amp with fixed bias, you can reach a good power ( increasing the bias current) in class A.
Then, I wrote
"Otherwise is class B, near the cutoff"
I never said 180 °
Walter
Alright, so it is perhaps 181 degrees with half a degree of overlap.
By your definition this overlap period is class A. That is just wrong. An amp biased to decent overlap angles is AB. It is never A or B. That is the definition of AB.
B has very light overlap. A has none. Ever. So to say, if it ever gets to cut off whilst power continues to go up, it is AB. It is AB whilst both are conduction, and it is AB whilst only one side is conducting.
When these definitions were created, none of the authors thought that there would be so much listening to the Marketing departments.
cheers,
Douglas
By your definition this overlap period is class A. That is just wrong. An amp biased to decent overlap angles is AB. It is never A or B. That is the definition of AB.
B has very light overlap. A has none. Ever. So to say, if it ever gets to cut off whilst power continues to go up, it is AB. It is AB whilst both are conduction, and it is AB whilst only one side is conducting.
When these definitions were created, none of the authors thought that there would be so much listening to the Marketing departments.
cheers,
Douglas
This EL84PP with 300 V supply voltage and 30 mA cathode current produce 19 W as maximum output power. Then grid 1 AC-voltage is 22 Vpp and operation is at AB.
At 10 W / 14 Vpp grid AC-voltage the output power is 10 W and plate current minimum is 2.5 mA meaning that the operation is now at class A.
At 10 W / 14 Vpp grid AC-voltage the output power is 10 W and plate current minimum is 2.5 mA meaning that the operation is now at class A.
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In my link of the amp I built there are the screenshot of the cathode current
That are the best test to see if it is in A or not. And when it is switching to AB
Then if we play with word, no problem.
Walter
That are the best test to see if it is in A or not. And when it is switching to AB
Then if we play with word, no problem.
Walter
Here the point when the operation moves into class AB. Grid 1 voltage is then 20 Vpp. It seems that almost 80...90 % of the operation range is into class A.
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To reach almost the 90% of class A the Ibias on my amp is 40 mA with around 290-300 Vdc.
This means that each 84 dissipates close to 12 watt
But my ratio on OT is higher than normal
Walter
This means that each 84 dissipates close to 12 watt
But my ratio on OT is higher than normal
Walter
bandersnatch,
Marketing has been smart for a Very long time.
Example:
Caveat Emptor, a Latin Phrase, precedes any vacuum tube amplifier classifications by hundreds of years.
I think the Class A versus Class AB naming conventions, 'what is called what & under what conditions' etc. has been over-discussed on many different threads on this forum.
Karl Barth once suggested ["Barth's Distinction"] that you can divide everyone into two groups:
Group 1: those who divide people into two groups.
Group 2: those who do not divide people into two groups.
You may agree with Barth or not; either way, you belong to either
Group A: those who agree with Barth, or
Group B: those who do not agree with Barth.
Which group [A or B] are you in?
If you don't like the A and B alternatives, you must belong to Group C.
Describe Group C.
IRMC
Marketing has been smart for a Very long time.
Example:
Caveat Emptor, a Latin Phrase, precedes any vacuum tube amplifier classifications by hundreds of years.
I think the Class A versus Class AB naming conventions, 'what is called what & under what conditions' etc. has been over-discussed on many different threads on this forum.
Karl Barth once suggested ["Barth's Distinction"] that you can divide everyone into two groups:
Group 1: those who divide people into two groups.
Group 2: those who do not divide people into two groups.
You may agree with Barth or not; either way, you belong to either
Group A: those who agree with Barth, or
Group B: those who do not agree with Barth.
Which group [A or B] are you in?
If you don't like the A and B alternatives, you must belong to Group C.
Describe Group C.
IRMC
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