Vacuum tube suppliers

Brent Jessee is very dependable, has a large inventory and offers very good advise.
http://www.audiotubes.com/12ax7.htm

Andy at Vintage Tube Services has the highest quality tubes and very high standards when selecting tubes. But you can only reach him by phone.
http://vintagetubeservices.com/

Upscale Audio is has very high quality tubes, and as a result, sometimes less of a selection.
https://www.upscaleaudio.com/collections/vacuum-tubes

* Brent Jessee now has a satisfaction guaranteed return policy; if you don't like the tubes, he will exchange them.

TC Tubes are one of the best.

Very highly recommend Jim McShane. Hand picked, fully tested and matched tubes and a great person to do business with.
mcshanedesign.net/tubes.htm

+1 Upscale Audio I've had great service, outstanding sounding and as important reliable tubes from them.

+1 Vintage Tube Services. I consistently get better sounding tubes from Andy than anywhere else. He meticulously tests, matches and cleans the tubes he sells. His knowledge of tubes, vintage equipment and practically anything audio is very impressive. As lowrider mentioned you must call him to place your order but that's always a pleasant and educational experience so I don't mind at all.