Yeah, I can't wait to find out if the 5751 acts like a 12AX7. I mean it tested so damn high, you have to wonder what the gain factor is on that tube? 5751's were made to run quiet, so if this has more gain than a regular 5751, in a ways it becomes like a 7025, which is an extra quiet, high gain 12AX7. This is probably going to be a V1 tube with say an RCA in V2. That should produce the blues sound you like so much. I've never tested that tube in an amp, so I am really more curious about its gain factor than anything else, but after all, it's a Tung-Sol.
I have taken a look at the tubes you sent me. Thank you, BTW.
The older Tung-Sol's were made with longer plates. Now they have short plates and the Mullards have long plates. The JJ's have long plates as well. One of my 602's came with two tubes marked, "Marshall" and the other two were Sovtek WA's. I can't stand the WA or the WB, as they both are prone to microphonics and they are screechy in the mid-highs. The shame is the Sovteks look like well made tubes. Their best AX7 is the LPS and it is not recommended for combo amps (microphonics). The LPS is sort of a copy of a ribbed plate Telefunken. The difference is that you can use the Telefunken in a combo without it breaking up. So just looking at the three brands, the Tung-Sol's are made with the combo in mind. Short, tight plates.
I got real busy with work and I have to take care of business first, but I will give these current production tubes a work out to say, "Mississippi Queen." I just haven't decided what amp to use. My TSL122 is gutted out in the back and it's easy to access all of the tubes, but I thought it would be fun to try some of this out on my 401. I know how it sounds, so putting different tubes in it will catch my ear right away...for the better or worse.
Stay tuned. More to follow.
Marty