Gedrrym5 gives good advice about Kevin. My experience with Kevin and the (French Mil) Mazda's is excellent as well. If you want the quietest and least expensive new tube, another option is the 12AX7 LP Sovtec. This is the ONLY Sovtec tube I like. It is a remarkable tube and a fraction of the cost of similar sounding NOS tubes. Other choices for an ultimate sounding 12AX7, is the Telefunken smooth plate. Be prepared to pay dearly for Telefunkens, as they are hard to find, and therefore expensive. Tele's are not necessarily the quietest tube around, but noise is more or less important, depending entirely on where it is used in a circuit. For instance, a Telefunken that would not be acceptable as a first stage gain tube in a phono circuit, could be the best tube available in a power supply, even if the noise numbers were not the best among the tubes you are testing.
