I've put this together, collecting up all sorts of things relating to the Cathodyne, mostly to answer the questions that I myself had, and to organize it in a way that it all made sense to me. Some of it I have posted before in my Super Champ thread,http://www.tdpri.com/threads/super-champ-1983-optimizing.473956/, but here it has been edited, clarified, corrected and expanded. I thought I'd share it, thinking it might of interest, or even help to some forum readers, although I'm sure a lot of it is basic "old hat" to many TDPRI bottle-head aficionados. I will present only a simplified examination of "HOW IT WORKS" and concentrate more on "HOW TO MAKE IT WORK" . Many text-books seem to cover the first very well, if perhaps somewhat technically, but not go into the second so deeply. The main concern of many Hi-fi related texts, is the mathematical analysis of the cathodyne's attributes, and how to calculate these figures. Although this can be interesting, the results are nearly all of little practical use to the hands-on builder of guitar amplifiers. As far as the technical assessment of the cathodyne goes, suffice it to say that the input impedance is so high as to be of little-to-no concern. Output impedance in the designs we are using is suitably low and well balanced. Distortion levels are minimal when not over-driven, and as will be discussed later, easily made controllable when they are. Also, as a lot of the text book coverage is from a Hi-fi perspective, with less relevance to guitar amp enthusiasts, they therefore tend to shy away from the 12AX7 in favour of better suited higher current, higher fidelity tubes. The post has grown longer than intended, but I hope my carrying-on isn't too long winded, I just didn't want to leave anything important out. Due to post size limits, I have split it into several parts. Please let me know if you spot any mistakes, and add your ideas and experiences with the cathodyne, especially if they differ from my postulations.