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.
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.