While working on the Spice model for a tube-based active crossover, I've done a lot of searches for tube data. One of the interesting things I've found is that Spice models have been used to show how sensitive many tube amplifiers are to their loads - Even more than I would have expected. Apparently, some of 'em are so sensitive that even cables can send them into oscillation. That's why some guys get so nuts about cables; There is some merit in this for certain amps. But then again, there are better and more reasonable ways to solve the issues described than to put focus on the cables.If interested, check out Norman Koren's article on the subject of tube Spice models, and his findings about feedback in these types of amplifiers too. These are published in "Glass Audio" and are quite interesting for those investigating tube amp design.
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