Tube noise when gain is increased, tube issue?

Most tubes have some noise, some less than others...unless it's humming or buzzing, and does not interfere with the music being played, I'd not worry too much about it.

I have about thirty tubes in my system… no noise… no hiss, no hum or buzzing what so ever.

I have the Freya, no hum or noise at any level. Guessing you have a bad tube. 

The Freya is known for this problem. Do some research and you will find that you are not alone. You might be able to find a better tube but you also might be chasing your tail. I have had 6SN7s prove noisy in Schiit products that are not noisy in all other applications and for this reason I will not retube any Schiit product. I have even hard clients that had Schiit "selected" tubes go noisy in a very short period of time. I had heard that they improved this component in this regard with later production units.

BTW humming and buzzing are not typical indications of a microphonic tube. Ringing and howling are more typical.

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...