Aric Audio Systems Unlimited Preamp

Rocray,

I have some Sylvania JAN 5751's that sound very nice in the unlimited.  The 5751 bring out the mid-range and the bass a little bit more and are supposed to have less gain.  They're very nice.

 I also have some Mullard 12a x7s. For all they're hyped up to be I didn't exactly find them all that great.  Maybe I just need more time with them.

@aricaudio,thanks for the recommendation on the signal tubes. I just popped in a pair of new Mullard 12ax7's. I find them to tighten up the bass a bit,and bring the mids just a smidge forward. So far they seem to work nicely. Always trying to kick it up a notch!

@jgoldrick,thanks for your recommendation as well. Funny how different things work for different ears. I will definitely look into a pair of the Sylvania's. I swear,this hobby is a sickness. ;)

Look here and scroll all the way down.
I found this chart to be pretty darned accurate . Maybe it will help some of you here .
This is for NOS tubes not new stock. 
https://tubeworld.com/12ax7.htm

Here are a couple of comparisons/reviews for the new stock 12AX7 tubes:

https://www.thetubestore.com/12ax7-tube-reviews
https://www.tubesandmore.com/tech-corner/12ax7-comparison-current-made-tubes

grey9hound and kalali ,thanks for the links. Very helpful.