Tube Question

2leftears, Most likely, it would be the ground scheme of the audio system itself and what is plugged into what receptacle and/or how any one piece of gear is grounded internally (some mix chassis ground with signal ground; some isolate one from the other), but you're basically right.

Invictus, Please tell me in what way your anecdotal report proves that tubes per se can be a prime cause of "hum"?  Let's be clear also, that when one uses the term "hum", it typically refers to 60 Hz or 120 Hz noise.  Tubes certainly can be noisy, especially aging tubes, but when they are noisy it's usually a mixture of many frequencies, which sounds quite different from "hum".  So, I guess a grossly defective tube that is shorted out could play a role in causing horrendous hum, but in that case you'd get no music at all.

Anyway, maybe the OP will come back and explain his problem more clearly.

I thought of one way in which a tube could cause classic hum as I defined it above: If you have an AC filament supply and especially if you are powering Directly Heated Triodes (DHT), the AC on the filament, which is also the cathode in a DHT, can be amplified and produce audible hum.  However, the cure is not to replace the tube but to fiddle with the filament supply or change over to DC filaments.

@jcbach , does your amp use a 3-prong power cable; the type with an earth ground? If so, try using a cheater-plug into the wall receptacle. This will eliminate the possibility of a ground loop.

@lewm My experience proves it. Had an integrated tube amp which used 6SN7 tubes. Ordered brand new Sovteks from Parts Connexion at the time and they hummed so bad it was impossible to listen to music. 60Hz hum and noise/buzz on top of it.

Replaced them with JAN 6SN7 and it was so quiet you’d have to put your ear to the tweeter to even hear the faintest of hiss.

Yes, garbage Russian and junk Chinese tubes can hum.

I had a similar experience with 300B tubes and many others.

Thank you for all your suggestions. lewm the sound is through the speakers. I've been told that tubes after 10 years should be replaced as they might draw way higher current and create a stress on the power supply and create hum. I've also been told that transformer noise is mechanical noise and would not be heard in the speakers. It seems like replacing the tubes is the initial way to go as the tubes I currently have don't seem to get high marks anyway.