But Leo tweaked them in ways that earlier designers had shied away from: he increased voltages, substituted components (so obsessively that Forrest White threatened to fire any of the assemblers who incorporated Leo's ad hoc changes in the assembly line), and, using feedback from working musicians, turned the guitar amplifier into a musical instrument instead of an electronics engineer's little toy. Were it not for Fender, and his ability to surround himself with talented and dedicated people, there would have been no rock and roll as we know it.Bingo. Look in the old tube books and you'll see where Leo got his designs.
On the other side, let's talk about something Leo constantly gets credit for, and had nothing to do with: he did not (despite all the craigslist and eBay listings to the contrary) design the Music Man amps. Tom Walker did that. Leo Fender's involvement, other than financing, was in designing and building the MM guitars and basses. Anyone who has owned a Music Man amplifier (and I did, along with -- currently -- five Fender amps) understands that it is a very different beast from the Fender. The early ones were all solid-state pre, except for a single 12AX7, with a tube power amp; later ones were all s/s preamp.