JAN (Joint Army Navy) GE, 5751 Tubes
From a famous reviewer of the JAN-GE 5751 tube: "While not really a 12AX7, it shares the same pin-out arrangement and is designed for less gain in favor of lower noise and microphonics. It works well in both preamps and can be used to advantage if your amp has too much grind or grain. One of these JAN- GEs should calm things down a bit. The 5751 is an affordable alternative to the 12AT7 ans in many hifi applications can slot in for 12AX7 as well In this application, you will get good gain with a warmer sound than the 12AT7. The even balancing makes them a nice phase inverter and allows you push the front end of the amp a little harder."
Lots out there on the net about these 5751s. We have used them here are the shop in place of 12BZ7 in a Cary amp as they are getting harder to find. Results were excellent as a simple phase inverter.
We have (2) matched sets of NOS JANs - $59 each or a matched set for $118 (sold individually).
JAN-GE (Joint Army Navy) 5751 Tubes: $59 each + applicable sales tax