No one cares about push-pull ?
Recently I was asked what topics the June issue would cover. My answer was that balanced to unbalanced con-verters and a review of inline push-pull output stages would be some of the topics for June. Disappointment made an appearance across my friend's face. "Oh," he said. Quickly disappointment was replaced by concern. "You know, no one cares about push-pull these days; just single ended. And forget that balanced stuff and write some articles about SE amplifier design," he counseled. I asked for an example. He paused and answered, "You know, something like how to design a SRPP input stage for an SE SV572-3 based amplifier. That's what we tube audio lovers want to read about." Concern was replaced with puzzlement when I asked why he wanted to read about push-pull circuits after all he had said against them. "The SRPP is a push-pull circuit," I told him.
My friend is not alone; few realize that the SRPP (AKA Totem Pole) and White Cathode Follower and Bridge output stage used in many OTL amplifiers are all just as much push-pull in function as the output stage of a Dynaco MK3.
Consequently, this month's issue covers a quick review of push-pull circuits. John Atwood continues his explanation of how series and shunt regulators work. We plan covering every aspect of regulator design in the upcoming months. Expect an article on how a hybrid shunt regulator can be built that uses an IC shunt regulator to set the DC operating conditions and a cascoded tube to control the AC aspects of the regulation.
This month we will also see how a balanced line stage can be designed to eliminate not only the common mode input noise, but its own power supply noise. Getting from balanced to unbalanced is covered as well.
Invitation for Articles
If you have ever run into a tube circuit problem that required thinking deeply about how the circuit worked to be solved, then you have the making of an article. Or if you ever have stared at a strange schematic until its function and inner workings suddenly it all came into sharp focus, you to may have a potential article in you. The key point is understanding. How does a circuit work is the focus. Maybe you have empirically found that carbon composition resistors at the cathode and tantalum resistors at the plate sounds best. But why? Is there some reason why the