I agree with Grannyring that hybrid amps come the closest to the best (high
powered) tube amps I have heard.
I use the Lamm M2.1 monoblock amps myself, which are very close
sonically to the Lamm M2.2 amps that two of my friends use. (These use
just one 6922 tube in each amp.) The best high powered tube amp I ever
heard was the VAC 300.1, and the Lamm M2.2 came the closest to equally
it, (compared side by side in the same system). In fact they bettered it in
the bass response as well as speed, but was not as good in the mid-range
or the treble response.
My two cents worth.
