Kiebert 300B 100 watt amplifier

Has anyone ever looked at this schematic?
https://i.pinimg.com/originals/8b/1e/00/8b1e00728ef12eb4be4d8b8aa7b075d2.jpg
Freed transformer was 18777, 100 watt rating 1650 Ohms on the primary

But more over a Quad of 300B's is generally considered to generate 45 watts or so I thought.

Full article is here
https://www.americanradiohistory.com/Archive-Electronics/50s/Electronics-1955-04.pdf

archeus6801-27-2020 5:13am

archeus68 OP Details Discussions Posts This discussion Message User 1 posts 01-27-2020 at 08:05pm Copy Comment URL Report Comment Edit Delete Thanks for a clear and concise response. I had stumbled across this collection of circuits and had never seen any of them before. Last year I did a quad 300B amplifier using the Brook 12A circuit as the front end driver. It turned out to be a really nice amplifier. And it did about 40 watts clean. Again thanks for a great reply.
atmasphere Details Discussions Posts This discussion Message User 11,803 posts 01-27-2020 at 04:23pm Copy Comment URL Report Comment Edit Delete Those power ratings are before the IHF stepped in during the early 1970s to standardize power ratings, by creating the 'RMS power' rating. By that method of measurement the amplifier at the first link will make about 50 watts. That circuit could stand with some changes! There are no stopping resistors at the input of any of the tubes. This can lead to oscillation which is why there are plate chokes and resistors in the output section. The input voltage amplifier is dreadful! It is a balanced circuit but has a poor Common Mode Rejection Ratio (CMRR). With less parts used, its performance could be dramatically improved by being operated differentially (which takes less parts). This would eliminate the need for the input transformer.