Buzzing or humming is usually from the transformer and can excite a noisy tube. If you don't need the extra gain, switch back to low gain, it is always quieter.
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.