Awesome, I agree as well. I have had the opportunity to look at very old Tube publications and I cannot find any place that touches on the topic of tube ratings in a holistic manner. Some circuits tend to stress tubes, and others operate them a bit cooler. The laws of superposition apply to Tubes as well. Not only are we to calculate the DC Plate Dissipation, but when Music begins to play, the average AC signal also creates and dissipates heat as well. So the sum of the static DC and the dynamic AC loads the plate. My best technical estimate is to attempt to leave some headroom so that the Tube can bias somewhere at 70% below Max Plate Dissipation so that there is headroom for the Music to play and create AC dissipation Heat to excite the OPT Primary. I go with my intuition as well, that operating close to Max, will shorten tube life. How much shorter, one would need to capture and measure statistical data. I don't have that time on my side, or Tube to cook. Thanks you your reply and the great reading!
Tube power dissipations, quiescent, and with signal, are one thing for push pull amplifiers, Class A, Class AB, and Class B, each one with unique numbers.
But now take a simplistic look at Traditional Single Ended amplifiers . . .
Quiescent:
The B+ voltage drops through the output transformer primary DCR, and the plate to cathode of the tube. Multiply that voltage drop times the quiescent current, that is the total dissipation (Yes, if the stage is Self Biased, then add the Bias Voltage x the quiescent current).
For example, 10 Watts Quiescent dissipation.
With Signal:
7 Watts is sent to the primary, and from there to the secondary (only 6 Watts of 7 to the speaker, if the output transformer's insertion loss is 0.5 dB).
And . . . 3 Watts remains in the tube. 10 - 7 = 3; 7 - 1 = 6.
Those are not exactly correct, but the essence is:
The quiescent power is there; Then when signal comes along, it robs power from the tube, and sends it to the speaker.
Perhaps that concept is one of the root causes for SE fans.
That concept, and my friends 212E single ended amplifiers, is what got me started back into tube amplifiers. Great sound, and those thoriated filaments lit up the room!
But now take a simplistic look at Traditional Single Ended amplifiers . . .
Quiescent:
The B+ voltage drops through the output transformer primary DCR, and the plate to cathode of the tube. Multiply that voltage drop times the quiescent current, that is the total dissipation (Yes, if the stage is Self Biased, then add the Bias Voltage x the quiescent current).
For example, 10 Watts Quiescent dissipation.
With Signal:
7 Watts is sent to the primary, and from there to the secondary (only 6 Watts of 7 to the speaker, if the output transformer's insertion loss is 0.5 dB).
And . . . 3 Watts remains in the tube. 10 - 7 = 3; 7 - 1 = 6.
Those are not exactly correct, but the essence is:
The quiescent power is there; Then when signal comes along, it robs power from the tube, and sends it to the speaker.
Perhaps that concept is one of the root causes for SE fans.
That concept, and my friends 212E single ended amplifiers, is what got me started back into tube amplifiers. Great sound, and those thoriated filaments lit up the room!