The Trainwreck Amplifier Company was built around a guy named Ken Fischer that built his own amps in the basement of his mothers house in Colonia New Jersey. Those amps are regarded as some of the finest that were ever made. I have studied and appreciated his work over the years and applied many of the design ideas and techniques to my own amp builds.
No discussion on amp design is complete without a mention of the RCA tube manual, first published in the early 1900’s. Every guitar amp circuit created can be traced back to the schematics published in the RCA tube manual. For guitar amplifier manufacturers their efforts were generally focused on creating tone controls and using various ways to combine the simple circuits provided in the RCA tube manual.