This valve amplifier is the next step in my Trans research, with earlier single-ended Trans designs published in previous audioXpress editions [1,2,3,4]. In this article, we present the new push-pull version (Photo 1). I say "we" because my TubeSociety students, Erwin Reins and Hans Gubbens, strongly supported this effort by making prototypes.
To start, I will provide a short summary of the Trans essentials [4]. Trans uses local feedback only around the power tube while the output transformer is outside this feedback loop. The power tube is driven by a voltage controlled current source plus one resistor R** between the anode and the control-grid. Then all the voltage amplification of the power tube is used to correct its internal distortions. Figure 1 shows a visualization of the Trans concept. The local Trans-feedback also makes the power tube's plate resistances very small, thus preventing magnetic distortions inside the output transformer [5].
In summary about Trans: Its local feedback is a soft local feedback technique that lowers power tube and OPT distortions. Years ago, when I started with Trans, I said: "I have gold in my hands." This observation has not changed during the research that has followed.
Power Supply Demands
The great advantage of my earlier published single-ended amplifiers is their constant current demand. The power supply can be simple, however, it needs good hum-rejection. The B+ voltage will not change under loud or soft music reproduction.
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Esta historia es de la edición May 2023 de audioXpress.
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