So I bought a Pro-ject Pre Box RS... (Valve suggestions?)

I think we can figure out what you’ve got. First the 7L means you’ve got two 6922s. You can find that code on page 13 of the pdf. Many changes were made to 6922s over their production life so this is reflected in the change codes of 8 and G. Letters were sometimes used when they went past 9 versions of the tube.

The first tube was made in Heerlen, the triangle indicates that. The next 3 characters give the date it was made, 1F4. I think it was probably 1971 because they started using the 3 character date code in 1962 or 3. The F is for June, the 6th letter of the alphabet for the 6th month of the year and the 4 means it was made in the fourth week of June. They weren’t as precise about dates as we are in the digital age.

The second tube I think was made in the US.  Phillips bought a factory in New York to be able to sell to the US military, who wanted their tubes to be made in America.  At least some of them, they also bought foreign made tubes.  I think the factory code is an asterisk *, which indicates the Amperex factory in NY.  You can find these factory symbols on page 5 of the pdf.  I think it was made in June of 1963.  More detail about the labels and construction could nail down the dates.

Heerlen tubes are usually described as having a lively sound and especially good in the midrange.  The American Amperex are also considered very good tubes, maybe a little more subdued than their Dutch brethren.

These are just generalizations though, and the only way to tell how they'll sound to you, in your system, is to try them out.  Differences may be subtle, but both pairs are considered very good tubes, so roll them in and enjoy!

I am still burning it in, as it came from factory.. It turned really muddy, but I am leaving a signal run through it, even if not at usual listening levels.
Currently it is either sounding better than it was out of the box or my audible memory is shot (left myself wide open, even chambered the bullet). I'll tube roll after burn in is completed.. a few hundred hours aught to do it? Should be about a fortnight, or so.

Thank you for so much information, much appreciated.

tomcy6
I'm flying back to visit family in Australia, and while I'm gone I was seriously considering cryo treating my speaker cables and interconnects.
Should I send the valves in with it? Had any experience with doing that?