I know this is a late response; but...
I’ve had the same problem with my Freya+; chased it around awhile and in the end replaced ONE tube. End of problem for the last 2 years...
Tube noise when gain is increased, tube issue?
Adjusting gain on my preamp improves the sound vibrancy who makes it sound better. But when I turn it higher the tubes tend to make a buzzing/humming noise which goes away when I turn it back.
Is this a tube problem or a gain problem. It's nice to maximize the gain setting before distortion occurs.