Hi all,
Rather than reading a bachelor-degree thesis in German, I highly recommend:
Merlin Blencowe.
Designing Tube Preamps for Guitar and Bass. Second Edition, Wem Publishing, 2012. ISBN 978-0-9561545-2-1.
It's pitched at the level of an electronics tech, but written by an MSc so readers would most definitely benefit from additional EE courses, some types of physics courses, etc. because these courses help in seeing beyond what is literally written in the text. Reviews of this book, including those by EE's, often state that this is the best book on the market.
I agree completely, and I do have Richard Khuenel's books which I would classify under Blencowe's description of "very technical books that are not really practical and seem rather to miss the point."
Op. cit. page vii. Richard's books are very thorough, but IMO very few people are interested in looking over what could be regarded as an very extended homework assignment in circuit analysis --- homework problem after homework problem done in a very pedestrian manner: input impedance, output impedance, frequency response for low freqs, frequency response for middle freqs, etc.
Blencowe's work as a "soul" so to speak. It's more a work of both art and engineering.
Regards,
Dave Clark