Mooreamps wrote:I was inquiring as to what his electrical background was, but glad good ole Jim was a drummer too.
Actually, Jim Marshall didn't do the electronics design side, such as it was. He just ran the business and gave drum lessons (incuding to Hendrix's drummer). Ken Bran was the chief engineer. He was an EE who had also worked as a guitarist in some bands. His main job was to figure out how to adapt the 5f6a Bassman design to be manufactured with components available in Britain, particularly for the transformers and tubes. So they changed early on from 5881s to KT66s. He also put a 12AX7 into the preamp for more gain.veets wrote:I think that the most significant aspect of Jim Marshall's electronics background is that he COPIED an existing design (Fender Bassman) when he built his first amp.
I think most people would agree the change from 5881s to KT66s was the first big turning point, and one of the reasons for the killer tones of the JTM45. The change to EL34s came later, as Marshall also started to gradually move further away from the Bassman design.morcey2 wrote:I would just like to thank whomever made it difficult/expensive for Jim to get KT66's and have to switch to the EL34. As they say, the rest is history.