Quote:
Originally Posted by kalee20
A simple, single-ended triode operated with a fixed input level (which is small enough that clipping never occurs) gives its maximum power when Rl = ra. This is the Max Power Theorem at work. But if you allow yourself to always vary the input level up to the point at which clipping occurs - whether it is grid-current clipping, anode current cut-off clipping, or clipping due to the anode voltage 'bottoming' then max power is reached at quite a different value of load.
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I think that a lot of misunderstanding has been created in the minds of electronics students when generations of lecturers have explained loudspeaker matching in terms of the maximum power theorem. Maybe back in the day of low impedance triode output valves it could give a reasonable approximation, but ever since the pentode came along, it's been irrelevant and with transistor amplifiers could result in the release of much magic smoke!
Martin