In Reply to: rectified cathodes and "ground" posted by hifitom on October 31, 2001 at 22:56:18:
Interesting questions...As long as the driver and output tubes are cap or IT coupled, having their cathodes at different potentials won't matter. The grid on the output tube is only interested in the relative diff between itself and the output cathode. Same for the driver. I haven't thought it through enough to answer for direct coupled.
If you "ground" the driver at the cathode of the output tube you will need to increase the B+ the driver sees by the same amount as the drop across the output tube cathode. For example, if you drop 60V across the output tube cathode resistor (or whatever), then you will need to boost the driver B+ by 60VDC to make up the loss between intermediate ground and ultimate ground (which is all relative - woo).
Now for the opinion part - by grounding the driver at the cathode of the output tube you're effectively putting the output cathode resistor and cap in the driver's return to ground - adding stuff in that path is usually not a good thing sonically. Most folks are trying ways to reduce the parts count twixt cathode and ground.
Others may have different views,
Pete
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