Early tube radios were powered by batteries.
That is where the term B+ comes from - it is shorthand for Battery Positive and is a holdover from the old days of battery powered tube radios. B+ is the high voltage dcv that is used on the plates of the tube.

To clean up the line signal it is easy enough to use a line conditioner. Lots of bars have really shitty wiring and lots of neon signs which can cause noise havoc, same thing with outdoor festivals...often run off really crappy generators.

The amps with rectifier tubes aren't really any noisier, and they can have a really nice blooming feeling when played hard. You can use a solid state rectifier in place of the tube rectifier if you wanted and that gets rid of the rectifier tube sag. The power transformer in itself does not add noise, but if the wires within the amp are not routed thoughtfully it can add noise by induction. Good lead dress techniques help reduce this a lot.


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If I should ever die, God forbid, let this be my epitaph: THE ONLY PROOF HE NEEDED FOR THE EXISTENCE OF GOD WAS MUSIC - KV