tubes for CAL Alpha

Anyone has opinions/recommendations on tube tweeking of 12AX7 tubes in California Audio Lab Alpha DAC ?
Also any difference in sound between non 24/96 version and 24/96 version ?
I absolutely prefer EI12Ax7's over all others that I have tried. Crystal clear highs, smooth mid range, excellent bass. Not romantic not cold. Amoung new production tubes these are my 1st choice. Others that I have used include Sovtek (old style and new LPS), EH's, Teslas, and some of Chinese origin. Also, if you get interested in EI's, the Elites are hard to come by but don't let that discourage you as the non elites are just the same tube with a little less screening and hype. And they can be found for less tha $10.00 a tube. On the older EI's I marginally prefer the grey plates over the newer polished plates.
My Alpha came stock with such crummy "china" tubes that anything would have been an improvement.
I've had the best success, by a wide margin, using Sylvania 5751 blackplates in my Alpha. Female vocals are amazing with these tubes, as are vibes, piano and strings. On the other end of the scale, Mullard CV4004s and Telefunken 12ax7s didn't do much for my ears--distinctly grainy sounding. For current production tubes, I haven't tried the Ei 12ax7s that Newbee recommends, but have popped in a pair of cryo'd Electro-Harmonix, which were pretty good.
I second the Sylvania 5751's. I've only put them into my DAC recently but I can clearly say right now that it's the best my Alpha has ever sounded.

For a second-choice budget tube, I'd recommend either a JJ 12AX7 or Sovtek 5751. The JJ is a little more transparent, the Sovtek has more richness.

I also found the famed Mullards to be rather dull sounding.

Good luck!

Another vote for the Sylvania 5751. In particular, I heard the Sylvania Gold Brand grey 5751 and it sounded amazing - musically balanced, detailed, nuanced, wonderful.