tube amp noise

No, I don't think that is normal.

Given that you've changed the tubes with no improvement, I'd have to say that unfortunately it will probably be difficult to isolate. I would think the most likely bet would be a capacitor or other component that has to handle high voltage, and is starting to break down under that stress.

But external sources would be possibilities as well, such as rfi/emi being picked up through the air or the power line when an appliance or other high current device elsewhere in the house cycles on or off.

Sorry I can't offer any more concrete suggestions.

Regards,
-- Al

If you gently tap on the faceplate do you get any noise? If your tubes are going microphonic, they'll definitely be noisy.

Sometimes, however, this could be a sign that the tube sockets themselves have some slight corrosion. Removing and re-inserting the tubes a few times might clean up the problem (and it's a cheap fix!)

HTH

I would also double check the fuse to see if there is some slight coloration on the glass.

How many tubes do you have to replace?

Same thing happened to me. New preamp unit and some hissing with popping noise once in a while. Even after tube rolling.

Happened to be an interconnect problem. The connectors themselves got a little loose. Tightened them and the problem was solved.

Another possibility that was brought to me by a technician is older cabling. An old interconnect that has remained plugged and untouched for many years can break inside its shielding sleeve without any apparent marks once it is moved or twisted again. Witnessed that problem at my friend's place when he changed is amplifier.

Hook up to a expendable pair of speakers and gently wiggle each tube and you will likely find a bad socket. The tube which swims the most is likely the bad site. Also, look for leaky capacitors, brown goo, oozing from the end. Jallen