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.
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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.