Tubes ECC88/6DJ8? Need all the help I can get

In principal I'd agree with Newbee's advice. However, if you are new to tubes it may be difficult to know and describe potential differences without actually rolling tubes (swapping out one for the other in sucession for the sake of comparing the sound) and hearing the potential for differences among tubes yourself. Yes, you should definitely listen to stock, but you'll never know how different it may sound without comparing, and if you have the time, money and inclination it can be fun. Then again, if you like the way it sounds stock, as Newbee suggests, you can also save the time and money if you are not inclined to tweaking. As a VERY general rule of thumb the stock tubes most manufacturers include with their gear CAN be improved upon (most new tube gear that I'm familiar with comes with either current production Russian or Chinese tubes). I'm sure there are exceptions and I'm not familiar with the amp you mentioned so I don't know. Don't know ECC82/12AU7 tubes either, but, again, I'd talk someone like Jon to find out what he thinks for your application. Good dealers know their tubes well. By reputation I'd pay attention to the Mullard and Tungsram tubes in that family. Also, your friend who recomended JJ's may have been referring you to the NOS ECC802S which is a tube JJ Tesla designed specifically for audio use (the 12AU7 design was not originally designed/intended for audio applications, as I understand). Anyway, that JJ tube has a pretty good reputation. Again, no personal experience with this tube family, so I'm only telling you things I've read and recall. Have fun!

I am having fun already! As you all know, this is what audio is all about. I will listen to the original tubes of course and, much probably, keep them for a while. But, as I told before, this is a new world for me. And quite an interesting one. Meanwhile, I have visited audioasylum and I am starting to get the picture: 1. NOS better than current production tubes; 2. NOS are many times fake! 3. And some good models like Amperex 7316... One more thing: if the original tubes are ECC82/12AU7, I suppose I have to use this and only this tube type - am I correct? So what about NOS ECC802S as Jax2 mentioned: same family?

Yes, ECC802S are simply 12AU7's that JJ Tesla designed specifically for Audio applications. They are in the same family and should work in any audio application that requires the 12AU7 tube. See them at the bottom of the 12AU7 list at the Tube Store link I listed.

AudioAsylum is certainly another good resource for information (as well as misinformation). The picture you describe is a very broad generalization, and is not an inaccurate generalization. But there are current production tubes that are excellent choices among specific tube types. NOS tubes are indeed counterfitted (plenty available on eBay to choose from:-). Tubes are also sometimes re-Branded. Also, many manufacturers have some tubes manufactured in different factories in different countries (ie just because it is a Telefunken doesn't mean it was necessarily made in West Germany). For instance, I have some Telefunken E88CC tubes that were made in a Mullard factory in Enland, yet they are marked Telefunken and are not counterfits or re-brands. I have Amperex 12AX7 tubes that are marked "Made in England", that are actually manufactured by Tungsram and were made in Hungary that have been re-branded. Both of these are excellent tubes BTW, even though they are not "accurately" labeled. On the other hand I have a GZ34 rectifier tube that is marked as GE made in England (which should be a Mullard-made tube), but it does not have the hole in the base (a sign of a genuine Mullard GZ34), and has a telltale raised "X" seam on the top of the tube indicating a Japanese counterfit. A very similar kind of "X" seam (though not identical) can also be found on legitimate Siemens tubes which are not counterfits. So, once again, it is good to deal with a tube dealer you know you can trust if you are new to this. Your searches here and on AudioAsylum should give you some good general feedback to go on regarding specific 12AU7 recommendations. Again, good dealers know their tubes VERY well also, and may even know your specific component. Always keep in mind, just as in all aspects of this hobby, there are no hard and fast rules and YMMV. Use your own ears and system to make your own judgements.

I absolutely agree with your last statement for (for all, not only tubes, audio matters). And yes I have seen these ECC802S at the bottom of the 12AU7 list at the Tube Store link. I must confess I like this "designed specifically for Audio applications" concept. But I have one other silly question... These tubes are sold seperately, by unit. What about tube balancing? I am sure I will be glad to talk to Jon also (thanks for the tip Jax2) when I feel prepared to replace my stock tubes for new (that is old) ones.

Most dealers will sell you a "matched" set of tubes if you request that (I think that is what you are referring to by "balanced"). Some charge a small fee to match tubes, and most have good equipment to accomplish that. Not a silly question. The more expensive tubes are often priced per unit.