These books are really worth their money. The Preamp book is already available in the second expanded edition and both versions are very good - also next to each other. Sample reading can be here: http://www.valvewizard.co.uk/
A very useful formulary for this hobby.
Antique! The plans as a handbook. In the internet era, no longer necessary, but ...
A book with information content, which is common. But you should know what you're doing, because not everything is well-founded. For example, the modification of the Hot Rod Deluxe is partially incorrect. Also it is about guitar ... that should not be forgotten.
Boris (drstrange) has translated a book about tube amplifiers by Gerald Weber into German and also made it available for this site. It is quite entertaining to read.
Access: # weber ## asx-dlmxQ #
(Explanation: # name ## pass # / just leave out the # )
Note: This is a technical novel, not a technical textbook!
Although Mr. Weber has experience but obviously little expertise. The mostly rather amusing statements in dogmatic style usually remain unassigned. This does not mean that you can not catch suggestions from the book. If you are not familiar, you should be rather careful.
Incidentally, Gerald Weber has nothing to do with the Weber speakers. That was Ted Weber, unfortunately already deceased.