For those interested...
http://www.e-insite.net/ednmag/inde...250&text=get+more+power+with+a+boosted+triode
http://www.e-insite.net/ednmag/inde...250&text=get+more+power+with+a+boosted+triode
François said:
This is another wonderful PSPICE simulation that looks good until you start wondering how you would actually implement it. Do you actually have a floating 100V supply in your amplifier? And if you add one, will you be able to drive the capacitance from the secondary winding on the mains transformer to ground?
This is speculation, but...
Imagine that you had 200V on the anode of your triode. The electric field from the anode would strongly attract electrons, and a considerable current would flow. Similarly, if you have a tetrode, and apply 200V to the screen grid, it will attract electrons strongly. However, the screen grid is very open, so it only captures a small percentage of electrons - most pass straight through to emerge as anode current. The key difference between this and tetrode mode is that the screen grid is driven by the audio at the anode, so as far as the control grid is concerned, it is a virtual anode.
One possible way of implementing the idea in an output stage would be to wind a secondary winding bifilar with the primary to give a 1:1 ratio, then feed it from the low current g2 bias supply stacked on top of the main HT supply. Unfortunately, most tetrodes and pentodes are designed to be operated with the screen grid at voltages below the anode voltage, so the principle doesn't seem very attractive.
Imagine that you had 200V on the anode of your triode. The electric field from the anode would strongly attract electrons, and a considerable current would flow. Similarly, if you have a tetrode, and apply 200V to the screen grid, it will attract electrons strongly. However, the screen grid is very open, so it only captures a small percentage of electrons - most pass straight through to emerge as anode current. The key difference between this and tetrode mode is that the screen grid is driven by the audio at the anode, so as far as the control grid is concerned, it is a virtual anode.
One possible way of implementing the idea in an output stage would be to wind a secondary winding bifilar with the primary to give a 1:1 ratio, then feed it from the low current g2 bias supply stacked on top of the main HT supply. Unfortunately, most tetrodes and pentodes are designed to be operated with the screen grid at voltages below the anode voltage, so the principle doesn't seem very attractive.
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