Yes, there are gold EH6sn7s. I have one. I bought 4 EH6sn7s at CES. They didn't have enough of the regular ones, so I bought one gold one. The gold referes to the pins being gold plated. The EH rep assured me that there were no internal differneces betwen the gold and regular 6SN7s, just the presence of gold plating on the pins. I don't know if the gold makes any differnece in sound. I think the only reason for the gold is for corrosion prevention, as the tin plating (I'm guessing that's the standard finish on non-gold pins) may oxidize over time, and reduce contact conductivity. Gold, on the other hand, doesn't corrode, as evidenced by gold items that are recovered from ancient shipwrecks that are just as shiny as the day they wer made, and the ability to find golod nuggets in nature, whereas other metals must be refined from ore.
In any event, I'm not convinced gold is the way to go, unless you also have gold plated tube sockets (Do these exist? I don't know). The reason being that when dissimialr metals are placed in close contact to each other, the one less prone to corrosion will cause the other metal to corrode faster than it would on its own. Since gold is the least likely of al lmetals to corrode, it can cause other metals to corrode more rapidly. This effect is much more important when the metals are in contact with water, but it can't help. I think I'm better off using tin pins in tin sockets. Where the pins aer actually in the closest contact will probably not corrode, since there is no air for oxygen to get in. Everywhere else on the pin will oxidize a bit, but these araeas are not conducting anyway. When you remove and reinstall the tube (for whatever reason), the scraping of the pin in socket should clean the oxide layer off.
I'm using these tubes in a pair of Atma-Sphere MA1s. They replace the stock Chinese tubes. Although I don't have enough tubes to retube both amps, comparing one amp w/all Chinese tubes to one w/ 4 EH tubes, the EH one sounds a bit more resolving of detail, and has tighter bass. The difference was not huge, but noticeable.
I guess your original question is still unanswered - does the EH sound better than the NOS because the NOS is worn out or because a good EH sounds better (in this situation) than the perfectly good NOS. Good question. Sounds like you need a tube tester.
In any event, I'm not convinced gold is the way to go, unless you also have gold plated tube sockets (Do these exist? I don't know). The reason being that when dissimialr metals are placed in close contact to each other, the one less prone to corrosion will cause the other metal to corrode faster than it would on its own. Since gold is the least likely of al lmetals to corrode, it can cause other metals to corrode more rapidly. This effect is much more important when the metals are in contact with water, but it can't help. I think I'm better off using tin pins in tin sockets. Where the pins aer actually in the closest contact will probably not corrode, since there is no air for oxygen to get in. Everywhere else on the pin will oxidize a bit, but these araeas are not conducting anyway. When you remove and reinstall the tube (for whatever reason), the scraping of the pin in socket should clean the oxide layer off.
I'm using these tubes in a pair of Atma-Sphere MA1s. They replace the stock Chinese tubes. Although I don't have enough tubes to retube both amps, comparing one amp w/all Chinese tubes to one w/ 4 EH tubes, the EH one sounds a bit more resolving of detail, and has tighter bass. The difference was not huge, but noticeable.
I guess your original question is still unanswered - does the EH sound better than the NOS because the NOS is worn out or because a good EH sounds better (in this situation) than the perfectly good NOS. Good question. Sounds like you need a tube tester.