TWhen Rudolf Moers discovered tube amplifiers, he could not find a good book that explained various concepts like the Ultra-Linear circuit, from a theoretical as well as a practical perspective. So he decided to write one, which he did: an 800 pages+ tome on everything tube (reviewed in Linear Audio Vol 2). In this article Rudolf further develops the theory and concepts related to ultra-linear pentode amplifers. The article also gives a clear comparison between triode, pentode and ultra-linear amps with regards to issues like distortion and output power, using the screen tap ratio as parameter. Extensive use of narrated figures clearly explains the issues; while all test setups are documented for those wishing to do their own measurements.
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