If you need total silence, brand new selected tubes from a careful dealer, is the way to go. If you don't mind the occasional noisy tube nothing beat NOS for tone amongst other qualities. For 12AU7s try the Amperex cwhite lable and their are too many others to count,for quiet and strong you might get from Telefunken ECC802S but they are not cheap. If the pre is a loud one with gain to spare try some 5751s in place of your 12AX7s
Jadis DPL Tube Preamplifier
I recently bought a DPL which I am currently re-tubing. Just ordered a set of EH 12AU7 and 1 EH 12AX7, but am wondering how the (NOS) new old stock Philips would sound? Any comments on the NOS? Also my preamp was looking a bit dingy so I had it polished and looks like it could be brand new but the gold coating on the faceplate was buffed right off. I really don't have to do anything to it, it looks perfect but in the future should I have it re-plated with gold or is it possible to buy a new gold faceplate along with 3 gold knobs that might be available from the manufacturer when they were made? Deb