Best Tubes For Cal Alpha DAC

I'm looking to replace the tubes in my Cal Alpha DAC. Any suggestions?
thanks for your time
I purchased a used Alpha from someone via the net. While they sent me the original tubes, the unit arrived with some tubes in it that supposedly were purchased from Audio Research Corporation ( ARC ). Since i also own two different Sigma's ( 16 bit and 24 bit ), i'm pretty familiar with the basic "CAL" sound. Having had them for a while, i have tried a few different tubes in them before. As such, these tubes DO sound very good in this unit. While i don't know if they really came from ARC or not, or if ARC "gain matches" or "hand selects" their tubes, etc... they are Sovtek 12AX7WXT's. I know that Parts Express sells these and i think that they can probably be ordered in matched pairs. Hope this helps... Sean
Hi Greg...I also have an Alpha. I've tried several NOS tubes and like the Mullard CV4004s the best. I was actually going to sell the Alpha until I heard these tubes. It now is a 'perfect fit' in my second system. They improved soundstaging, brought out more detail and just made the music sound a little more 'analog-like' as compared to the others. BTW...these are also the tubes that Kevin Deal at Upscale Audio recommends for this unit. Good luck in your search!
I tried the Mullard and another tube from Kevin. I prefer the Sovtek's mentioned above. Then again, there is QUITE a bit of personal preference and system synergy to take into account here, so obviously opinions will vary. Sean
The Mullard is the fav...but it's all synergy. We have retubed a lot of those. The Mullard was the fav...then there was a burst of Brimar buyers....but some folks felt the brimar were too the pendulum swung back to Mullard.

If you want more sparkle, try the GE long and a very well made tube. Creamy and fat? Try the early 1961 vintage Sylvania (which sound nothing like the later Sylvania). Both are about $20.

PS - my recommendations are based on feedback...I don't sell cal Audio...I do know that people had called there years ago and the Mullard is what the factory was sending them to us for.
Using RCA 5751 and like them.
Has anyone used a RAM tube in your Cal DACS before?
1963 GE Large plates are amazing! What a difference in soundstage. Everyone recommends the Mullards, but the GE's are 1/2 the price, and are quite an upgrade over stock.