Quote:
Originally Posted by vampyretim
... When I pull the EF86 out it kills the hum.
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That's a brave thing to do with the Mullard 5-10 (actually pulling valves out is a pretty brave thing to do with any piece of kit). The EF86 anode is DC-coupled to the grids of the following triodes. The grid potentials will go positive until the grid current through (what used to be) the EF86 anode load and HT dropper stops them. I'm not sure how much grid dissipation an ECC83 is rated for, but it may not be very much.
Cheers,
GJ