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In Reply to: RE: Thinking about running my non-OTL Circlotron again posted by Tre' on August 24, 2011 at 10:26:09
Yes- unless you simulation does not reflect the actual circuit."
Are you trying to say that a tube can conduct in the negative?
No, and no idea where you got that idea either.
Follow Ups:
You said that there was no "flat spot at the bottom of the curve" and maybe there isn't.But the lower half of the waveform would have to be truncated at anything above 5 watts for a M-60.
Majorly truncated at 60 watts.
Whether it's flat or rounded makes no real difference.
The main point is that it's not the same shape or size as the top half of the wave form, it can't be without the tube being able to conduct in the negative.
In a real Class A (1 or 2) circuit both halves of the wave form are the same (or very close to it).
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/24/11
Tre': So what term would you use to describe that particular assymetrical waveform above 5W output (because we know that an M60 makes more than 5W)? Is that waveform a hallmark of Class AB or B operation? I do not think so, but enlighten me. Thanks.
If the tubes don't completely cutoff some say that it's Class A.That's what the books say.
But if we read the rest of the chapter we find that there is more to Class A operation than that.
If we judge the class of operation by what is really happening I would have to say the amplifier is "acting" like a Class A/B amplifier.
Please understand that a Class A/B amplifier does not operate "like" a Class A amplifier up to a certain power level and then operate "like" a Class B amplifier.
Class A amplifiers are biased and loaded and driven in a certain way.
Class B amplifiers are biased and loaded and driven in a certain way different than a Class A amplifier.
Class A/B amplifiers are biased and loaded and driven in a certain way
that is different than either a Class A or a Class B amplifier.The three classes of amplifiers are distinct and not to be confused with one another.
What the "A" portion of a Class A/B amplifier has in common with a Class A amplifier is that the current can and does go down by the same amount (depending on the linearity of the tube used) that is goes up, giving a symmetrical wave form.
As the power level goes up the lower half of the wave form gets truncated.
The higher the power level the more (as a percentage of the total) truncated the lower half of the wave form gets.
This is exactly what happens in an M-60 above about 5 watts.
BTW most tubes are not linear near cutoff. The bias can go more and more negative but the current does not go down in a linear way.
This is called the cutoff region.
Once this behaviour starts the tube is said to be "in cutoff".
There are a lot of tube that "refuse" to cutoff completely without an extreme amount of negative bias.
Using one of these tubes does not make a Class A/B amplifier a Class A amplifier.
A properly designed and operated Class A (1 or 2) amplifier should not reach the cutoff region let alone total cutoff.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/24/11 08/24/11 08/25/11
Wrote the above probably at the same time you were posting your last two posts.
By the way, you guys have had this same discussion here within the past few years, and you used the very same figure to support your argument, which is fine.
" By the way, you guys have had this same discussion here within the past few years, and you used the very same figure to support your argument, which is fine."Yea, I did use that same figure.
That figure fits perfectly the full description given in all the books of what Class A operation is.
While it is true that a tube being operated in Class A does not reach cutoff that is not the end of the definition of Class A operation.
That figure is.
BTW Lynn Olsen refers to it as "deep" Class A. I and the books just call it Class A.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/24/11
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