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Keep up the good work. This is the most fun reading I've had on the subject of tubes. Your math looks very good to me, and your explanations are lucid. I don't know how anyone can argue if they actually pay attention and think. Maybe that's too hard, having your mind already made up is easier.
TJ
Once, I thought the 5% distortion limit to measuring an amplifier's output wattage a little too arbitrary: Why not 1% or 10%? Today, I embrace it wholeheartedly. And I would argue that we need a 20% rule for determining the Class A to Class AB transition point. We know that the advantage Class A enjoys over Class B is the flatter output impedance across the entire waveform that derives from both output devices working equally hard. Thus, my definition of Class A being simply the mode of operation wherein both devices continue to conduct over the entire waveform does not go far enough. It needs to be restated as "Class A is the mode of operation wherein both devices meaningfully continue to conduct over the entire waveform." When does an output device stop making a meaningful contribution to the power output? We could arbitrarily pick 20%, or even 50%, as the distortion limit to current waveform through the device. So that once this figure is exceeded, the amplifier is considered to be operating in Class AB.
It has been said that the world divides into two types of people: those who believe the world divides into two types and those who don't believe it does. With audiophiles, I have found the two types to be those who like math and those who don't. Of course, some go much further than just not liking math. I remember one audiophile asking what wattage the plate resistor in his amplifier needed to be and being disgusted
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with my answer: "I don't know. What's its value and how much current flows through it?" Apparently, a true tube guru would not ask such questions.
Over the years, I have had many audiophiles ask me for help with a circuit or design issue. Often, the best answer I could give them was a formula so they could supply the values for the variables and work out the best answer for their situation. Usually, the formula was immediately thrown away. (I remember one fellow acting insulted when I gave him the formula and him calling me the next day to tell me he had gotten the definitive, only correct answer from the designer of some obscenely expensive audio gear; of course, he had to buy some of the obscenely expensive equipment, as that was the answer. A year later he described this guru as a complete rip-off artist.)
Maybe, 20% of the time, the audiophile readily welcomed the formula and was thankful for the sharing of a secret formula, of course, there was no secret. That is probably the same ratio for this journal: 80% of tube loving audiophiles will quickly ignore it and move to a site that allows them to spend thousand of dollars.
Subject: VIRTUAL ZENER
I really enjoy the Tube Cad Journal! Thanks for sharing so many hours of personal effort with us. We should all be grateful. The 'zine is thought-provoking, to say the least...it is interesting to see that many of my own over-the-edge ideas and concepts are showing up in the 'Journal. Seems we are on similar wavelengths...
You have sometimes referred to the use of a "virtual zener" instead of the real article to keep broadband power supply noise down. I, too am a proponent of eliminating zeners wherever I can, and was curious as to what you are doing.
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