In 1974 Music Man came with a hybrid amp designed by Leo Fender and Tom Walker. It is the Music Man Sixty-five .
They combined solid state technology with tube technology . The amp came with a solid-state preamp and a tube power amp. Mark Knopfler, Eric Clapton and many others used Music Man amps.
Music Man Sixty-five 210
More about the Music Man Sixty-five you can you read here
Basically there are 2 kind of hybrids:
- Hybrid with tube preamp and solid-state power amp
- Hybrid with solid state preamp and tube power amp
But after the invention of modeling amps, manufactures started to combine modeling amps with tubes.
Vox Valvetronix for example. They use a dual triode 12ax7 tube in the power section of the amp.
As a result you have all the benefits of modeling combined with the characteristics of a tube!