If the transformer noise is physically coming from the transformer itself then it is DC offset and can be eliminated easily enough. You can try turning things off until you find the culprit, or just buy a DC offset eliminator.
Tubes themselves are so highly variable you can pay a fortune and still get crap or you can go cheap and pray they last forever they sound so good. I've rolled more than a few and while yes they do make a difference the difference they do make is tiny in the extreme. If you want better sound skip the tubes, get a better amp.
Regardless which way you go on that one tubes can be noisy but I have yet to hear one hum. Usually its a faint whoosh or more often a crackle that sounds like static but either way comes and goes never just steadily going on and on. So anything like that I would be looking elsewhere, like the DC offset, or hum from a ground loop getting in there somewhere.
Tubes themselves are so highly variable you can pay a fortune and still get crap or you can go cheap and pray they last forever they sound so good. I've rolled more than a few and while yes they do make a difference the difference they do make is tiny in the extreme. If you want better sound skip the tubes, get a better amp.
Regardless which way you go on that one tubes can be noisy but I have yet to hear one hum. Usually its a faint whoosh or more often a crackle that sounds like static but either way comes and goes never just steadily going on and on. So anything like that I would be looking elsewhere, like the DC offset, or hum from a ground loop getting in there somewhere.