Thanks. This is essentially what I read. This seems to agree with what I read on Head Fi, that using a GT or early tube in something that was designed for the later GTA/GTB types, could cause problems. What I read made it sound like you could damage your component, where this says that you may just ruin a tube. Some of these early tubes bring some pretty silly money and the gear is certainly not cheap. I'd hate to ruin either one.
Using a GTA or GTB tube in an older design piece of gear that was designed around the GT types is safe but this is not my situation. Still, tons of people have talked about putting the older GT's, W's etc. in modern components and they end up being their favorites. Most notable is probably the Tung Sol BG RP, seems to me the 40's or maybe early 50's. Can't remember but I'm guessing these are the older GT type. I have not taken that plunge yet, if you find them they generally run $200 each or more. So far, I'm getting plenty of enjoyment from tubes that have been $50 each or less.
There are several tube rolling threads several years back about the very preamp that i use, as well as it's other iterations. The tube compliments are the same in all of them, simply saying 6sn7 but always supplied new with modern versions, which I can only assume match directly with GTA and GTB types with 4.5 to 5w output. Nearly everyone agrees that the best tubes were the oldest, the ones made in the 40's that would have the lower output of 2.5w. None stated that their gear or the tube failed. I have seen a number of reported failures of the old Russian versions with metal base Melz 1578 and 6N8S, which are highly coveted but not without controversy. Many complain about noise which seems mostly attributed to bad solder (sometimes able to be repaired) and some have complained about early failures. Most of these tubes are 70's and 80's but there are versions back to the 50's as well. All speak of great SQ, if all in working order. I have interest in them but am hesitant as well. I have plenty of US made tubes to fool around with for now.
I have several of the older types but have not used any yet. I am enjoying several different varieties of GTA/GTB's but am looking forward to hearing the older ones that everyone raves about. I'd hate to think that they could be unsafe to use (for the gear) or that I would ruin the tubes themselves. Has anyone experienced any of these problems?