The short answer is most likely no. The tube filament is a small vertical (metal) element that is inside the cathode piece element of the tube. These round metallic pieces are assembled and cut manually before they are inserted and sealed inside a piece of glass. There are other pieces of metal ( grid, plate, etc.) that are put in place around the most inner piece - the filament, and supported by round pieces of mica. What happens is that these pieces are not cut and/ or assembled the same all the time. This creates the illusion of one filament being brighter than the other one. Sometimes even not equal inside the same tube ( dual triodes).
So, if you get sound coming equally from both channels you are most likely OK. If the filament is open (cut) and does not light up, then you have no sound and is time to change the tube. Same principal as a light bulb - no filament, no light!
Thanks,
Alex
