Here is an excerpt from a review at thetubestore.com:
The Tung Sol 12AX7 has the gain and drive of a Chinese 12AX7 and the pure tone of a Mullard or Brimar. According to the manufacturer, this Tungsol 12AX7 is the Ultimate 12AX7. Big, warm, and musical. High Gain, ultra-low microphonics, and superb linearity with a dynamic 3-D sound.
Here is a link to the review page (I think this has been posted before):
http://thetubestore.com/12ax7review.html
More opinions on TS vs JJ:
http://www.seymourduncan.com/forum/showthread.php?t=161220
@needleshy: PM sent
Skywalker wrote
Could you pop the JJ's in instead of the original Marshalls? Would it make THAT much of a difference? I can keep the Marshalls as spares then.
I replaced the old "Valve Art" EL34s with JJs and the old Marshall branded 12ax7s with Tung Sols. You need to let the Tung Sols burn in a bit and then roll tubes and see which you prefer. Preamp tubes can be rolled without having to rebias anything and thus easy for you to do.