Quote:
Originally Posted by Duke_Nukem
Not convinced. The current flow is primarily controlled by electrostatics and the mechanical construction, whereas the heater controls the size of the pool of available electrons around the cathode.
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It is indeed a little known side effect of reducing the heater voltage that it also increases the linearity of the valve, at the expense of gm. ra of course increases.
(I actually had my Ra and ra theory backwards in my earlier posts, so ignore that, I was being stupid). Obviously once you drop below about 75% of the normal heater voltage all bets are off, but for small reductions it holds true and is well worth doing in hifi because the reduction in gm is negligeable, while the additional increase in lifespan is also useful.