Tubes used in VTL 6.5 II preamp?

Hi -- does anyone know what brand 12AU7s VTL uses in the 6.5 II preamp?  Much thanks.

And if you have/had a 6.5 II and tried different tubes, would appreciate hearing your thoughts.
Thanks for the reply.   The tube brand is not in the manual, and have been unable to get the info from VTL, though I'll be buying a pair from them, and will find out when I get them.  Was just hoping to find out before purchase.  
They may be rebranded and not readily identified. Probably selected Gold Lion, Electro-Harmonix or JJs.
I haven’t heard the VTL, but if you decide to try NOS tubes, I really like the Amperex 7316. It’s a variant of the 12AU7.
believe the factory installed tubes are JJs. Dont have the 6.5 but do have the 7.5. You may want to try installing some PSVANE T-IIs. most open and 3-D tube I have tried so far.
You're  correct, it is JJs, I have confirmation now from VTL.   

I'll give the PRSVANE's a try, thanks for the tip.