This is my own opinion >> I always heard the solid tubes(at the time) were a
compromise. I had heard they got pretty hot and at the time didn't offer any
advantages over the tubes they replaced. Today, some of the 3rd mixer stuff
is better replaced with Sherwood mods actually.
I also heard they didn't sometimes work in the circuit as well as the
original tube.
This is all hearsay, since I have no experience with them. I think they were
pretty rare too. Plus that was 30 yrs ago so there may be a lot of better
ways to improve the circuits now.
73
Mark
W0NCL