Posted: Sat Dec 27, 2008 2:11 pm
SInce that amp's driver and initial LTPI stages run from 325V B+, it should be a good candidate for driving EL84s using the standard ST35 voltages. (365 to 380V B+ for the power tubes, and 325V for the VA and LTIP section)
I ran a sim on tubecad, with 12AU7s and with 6CG7s, and the 6CG7s come out a little better. The overall gain with 12AU7s seemed to be marginal for driving 6550s or KT88s to full power, but they have more than enough drive (even without the CF stage after the LTPI) for driving PPP EL84s.
Alas, it can exist only on paper for now, but next year...
/ed B
I ran a sim on tubecad, with 12AU7s and with 6CG7s, and the 6CG7s come out a little better. The overall gain with 12AU7s seemed to be marginal for driving 6550s or KT88s to full power, but they have more than enough drive (even without the CF stage after the LTPI) for driving PPP EL84s.
Alas, it can exist only on paper for now, but next year...
/ed B