I am reading through Merlin Blencowe's book on designing preamp circuits for guitar and bass. He offers two suggestions for reducing preamp noise and increasing signal-to-noise ratio: keep the grid stoppers as small as possible, and keep grid leak resistors as large as possible. He then describes a general medium-gain topology, and at the grid of the third gain stage he proposes the following arrangement. The 820K grid stopper seems large, and the 220K grid leak seems small. This seems to go against his recommendation of keeping grid stoppers small and grid leaks large.