I almost hate to get into this because I have found that the Telefunken tubes are NOT always the best of their type. Both the 12AX7 and 12AU7's have an unnatural thickness in the midrange. Only the ribbed plate 12AX7 (If you can find them) overcomes this problem. Yes, the ribbed plate 12AX's may be the best ever made, but, everyone loves the smooth plate Tele's and they are only the best if your system needs this flavor. As far as AU7's go, there is a Mullard tube which is better than anything else I have ever tried regardless of what circuit it is used in. I wish I could tell you which tube it is, but, honestly, I am just not sure. It is not the really old version which sounds great, but, a bit too rich and romantic, nor is it the later version which lacks magic altogether. This tube does however have the "old" style logo. Remember, there is more to a tube than it's manufacturers name. There were many incarnations of the Mullard 12AU7 through the years and they all sound different. I guess this also goes for most tube brands- I have some old Yugoslavian AX7's supposedly made on retired Telefunken machinary which sometime impress me as being even better than the ribbed plate Tele's themselves.
