by Ty_Bower » Thu Mar 24, 2011 9:17 am
Get some clear photos of the tube, especially any print near the base. Also get a photo of the key pin on the bottom of the base. As mentioned, International (National?) was known to rebrand anything they could get cheaply. In the sixties and seventies, that could have been highly regarded Mullards.
I've also seen National "5AR4" with big box plates that look more like a 5U4 to me.
"It's a different experience; the noise occlusion, crisp, clear sound, and defined powerful bass. Strong bass does not corrupt the higher frequencies, giving a very different overall feel of the sound, one that is, in my opinion, quite unique."