Reporting question for Vacuum Tube - EL84, JJ Electronics

Product:
Vacuum Tube - EL84, JJ Electronics

Question:
I bought the power matched pair and noticed that one tubes filaments glow brighter than the other, is this normal?

Answer:
A blue glow on the surface of the glass, mica, or metal is fine. A blue or violet cloud within the tube structure is bad. An orange glow from the filament or cathode in the middle of the tube is normal and can vary from very bright to very dim depending on how it is covered from view by the surrounding structures. A red or orange glow on the surface of the plate is bad and is referred to as "red-plating." This is caused by setting the bias of the tube too hot. If the tube was bad you would hear it.