I suppose it depends where the HT voltage is measured from eg: pre HT filter or post HT filter, the DC current draw by the output stage should be reasonably constant if it's operating in Class A, after the HT filter most of the valves will be under AGC control so the HT at that point could vary as the bias due to AGC action is varied on those valves.
A good description for AGC design/circuits can be found in RDH4 here: http://www.paleoelectronics.com/RDH4/CHAPTR27.PDF
Lawrence.
A good description for AGC design/circuits can be found in RDH4 here: http://www.paleoelectronics.com/RDH4/CHAPTR27.PDF
Lawrence.
