tomp wrote:
It is interesting to see all the machinations that need to occur to try to deal with an inherently flawed device like an output transformer. Then you look at the ZOTL circuit that David Berning uses to eliminate the transformer and all the associated warts they have. Much better way to do it and make sense of using tubes in a situation where impedances have to be matched. Transformers have their places but those places are getting fewer and further between every day.
Tom,
Using a ZOTL circuit is beyond most DIYers, and not even sure that Dave has the information for designing them in the public domain. Yes, transformers have their flaws, but nothing is perfect and designing around those flaws is part of the challenge. There is a long history with transformers, and information is abundantly available for building tube amplifiers with them.
Also, when it comes down to it, linear power supplies are also obsolete technology today, and switching power supplies in principle can be developed to perform better than linear power supplies. But they are complicated for the hobbyist to design and build, require greater attention to filtering, and require test equipment beyond what most hobbyists have. A linear power supply is pretty easy to design for filtering and low noise from 60Hz/120Hz input.
David:
This was a statement on output transformers in general, not specifically aimed at DIYers. I also still use linear supplies in a lot of my applications because design of a switching supply is beyond me. However, where it makes sense I buy commercial switchers with very high performance and low costs. Dealing with output transformers or the complexity of a DIY ZOTL are some of the reasons why I switched to solid state. To each his (her) own.
David