What tubes to use for Audio Research SP-9 MkIII?

I have the MKIII and NOS tubes are the way to go. The tube near the center of the circuit board is for your cd, tuner etc. The other tube is for the phono stage, so if you don't have a turntable you'll need just one tube. No, $130 for two Siemens is a bit high. You can get "made in Germany" RCA 6922 for about $25 - $35 apiece on Ebay. They were made for RCA by Siemens. The Siemens give an open, detailed sound at the expense of the bottom end heft. At the other end of the spectrum is the Telefunken E88CC (6922 European) and it will give you hefty bass and smoother sound but less detail. They run about $65 - $100 apiece. Amperex 6922 is somewhere inbetween those two but there are many versions of them, all designated 6922, and some are much better than others. Try audioasylum.com, FAQ, "Joe's tube lore" for more info on that. If you play music every day then leave the unit in "mute". That keeps the heater on so the tube doesn't have to cycle hot, cold, hot which is hell on tube life. The 6922 family is rated at 10,000 hours. Whether standby time (mute) is counted towards that, I don't know - info Anyone? Good luck.

Hello,
I've had my MkIII for about 5 years and have tried Telefunken,Mullard,Amperex,etc. I finally called ARC and got some of their stock tubes for the preamp, the Sovtek 6922. I use them with their tube dampers and to me the preamp has never sounded better. I'd suggest that you call ARC, tell them what equipment you have, the type of sound you're looking for, and they'll be able to help you. New tubes from them are about $25-$30. Another source for tubes and info is Upscale Audio.
Good listening.

Upscale won't sell any decent 6dj8/6922 types to people unless they bought their gear there. I'd recommend Amperex as the best tubes of this type...after all, they invented the 6dj8 frame-grid type of tube.

-Ed Sawyer
(Full disclosure: I have some of these for sale.)