I think I can answer that question. As you move up the line in the integrated and into the MRE 130 mono amps, the designer has chosen to step up the plate voltage as you step up into the bigger models. I have the specs for the integrated's, I will post later, however, I believe the MRE 130 has a plate voltage of 530 volts. I measured the output in milliamps of the recommended bias settings on the amp using the Tube Amp Doctor Biasmaster and measured .38ma for the desired bias setting according the manufacture. I was using KT88's. That seems to me a conservative reading. Of course, I can go higher in regards to milliamps, in fact I have, using KT120s in an experiment running at .65ma with no problems.
This is my belief, Octave uses a stepped up plate voltage approach as you go higher in the lineup, always taking into consideration tube life, equipment usability and robustness and ease of use. Essentially, plug and play concept of use. Perhaps the V40 is measured using the EL34 tubes and not the optional 6550 or KT88's. I do know that the plate voltage is a big factor and therefore as you move up the line, you get higher output. The two EL34's on the V40 do not output as much power as a pair of KT88's on the V70.
Ciao,
Audioquest4life
This is my belief, Octave uses a stepped up plate voltage approach as you go higher in the lineup, always taking into consideration tube life, equipment usability and robustness and ease of use. Essentially, plug and play concept of use. Perhaps the V40 is measured using the EL34 tubes and not the optional 6550 or KT88's. I do know that the plate voltage is a big factor and therefore as you move up the line, you get higher output. The two EL34's on the V40 do not output as much power as a pair of KT88's on the V70.
Ciao,
Audioquest4life