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To add to the comments about the dropping resistor in the 0V line providing a benefit for some forms of noise, this situation is related to parasitic capacitances between the power transformer HT secondary winding and a variety of capacitive paths back to 0V, such as via the transformer core, or primary winding, or electrostatic shield, or other secondary windings (eg. heater).
Capacitor noise current is proportional to the parasitic capacitance level, and the applied dV/dt. The HT winding has lots of voltage swing (dV) but at a somewhat low mains frequency (1/dt). Rectifier related hash/noise can be much higher frequency, although at lower voltage levels (depending on leakage inductance levels and current waveforms). Adding resistance to the loop that is closed by that parasitic capacitance, in the form of the additional dropping resistor, would be of some benefit to attenuating that noise current from flowing in the remainder of the 0V distribution (eg. to chassis for parasitic capacitances to chassis).
However the parasitic capacitances are likely to be small, perhaps up to hundreds of pF for transformer windings layered over each other.
A practical dropping resistor value is unlikely to be very large in comparison to the impedance of the parasitic capacitance, except at frequencies beyond audio range, and hence little benefit may be achieved. If that noise is a concern then maybe a few ferrite beads/tubes slipped over the 0V link between first and second filter cap, and the related HV DC dropper resistor leads, would be of similar or more benefit.
Capacitor noise current is proportional to the parasitic capacitance level, and the applied dV/dt. The HT winding has lots of voltage swing (dV) but at a somewhat low mains frequency (1/dt). Rectifier related hash/noise can be much higher frequency, although at lower voltage levels (depending on leakage inductance levels and current waveforms). Adding resistance to the loop that is closed by that parasitic capacitance, in the form of the additional dropping resistor, would be of some benefit to attenuating that noise current from flowing in the remainder of the 0V distribution (eg. to chassis for parasitic capacitances to chassis).
However the parasitic capacitances are likely to be small, perhaps up to hundreds of pF for transformer windings layered over each other.
A practical dropping resistor value is unlikely to be very large in comparison to the impedance of the parasitic capacitance, except at frequencies beyond audio range, and hence little benefit may be achieved. If that noise is a concern then maybe a few ferrite beads/tubes slipped over the 0V link between first and second filter cap, and the related HV DC dropper resistor leads, would be of similar or more benefit.
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