Re: Mullard 5-10 amplifier
Given the output resistance of the preamp is around 150k (680k // 180k), you could happily drop R1 to 470k. That should quieten the hiss a bit further without any other effect on performance.
__________________
....__________
....|____||__|__\_____
.=.| _---\__|__|_---_|.
.........O..Chris....O
|