Hello, I just joined, primarily for the audiophile products. Looking at purchasing the NHT C3 speakers for our new living room. Space is about 15 feet wide by 33 long and they will fire long ways. Space is just for general listening, music room with all equipment is downstairs, so hoping they will fill it with sound nicely. Cheers.
Mar 18, 2024
https://www.ebay.com/itm/6N5PJ-Double-Triode-Valve-NOS-Tube-fr-DarkVoice-Headphone-Amplifier-Preamplifier-/121959462818
My stock 6N5PJ also shows the same black coloration on the bottom. It doesn't effect its use. From my cursory understanding of tube audio it's likely the Getter for this particular tube:
" Flashed getter – The getter material is held inactive in a reservoir during assembly, then heated and evaporated after initial evacuation, usually by induction heating. The vaporized getter, usually a volatile metal, instantly reacts with any residual gas, then condenses on the cool walls of the tube in a thin coating, the getter spot or getter mirror, which continues to absorb gas. This is the most common type, used in low power vacuum tubes." (Wikipedia)