Also, another reason this would not work for the DRD amp is bias voltage for full output is 24V. For a DC coupled design, this may be a non starter if the current draw through the plate/grid choke drops more than 24V.
You can check the specs on Sophia Electric's site (http://www.sophiaelectric.com). A friend of mine who is an excellent designer and a former consultant to Sophia Electric confirms the unsuitability of this tube for 300B circuits.
David
