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Grid resistors

Indeed, grid resistors of the output stage may limit driver's Rp. Grid chokes might help though.

As to RF oscillation due to positive feedback, a good 2A3 design, with or without neutralization, should incorporate grid stoppers, or RF plate chokes, or a combination of both. These measures should prevent oscillation.

PFB is not necessarily evil in an audio amplifier, as has been discussed on this forum.

Here is a link to a practical high quality 2A3 amplifier utilizing neutralization in both driver and output stages:

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