Thanks for you guys help.
I have just bought used pair of VPAs and have listened only 3 days, actually around 10 hours, and using them with Meridian G08 CDP & Clearaudio TT, Nagra PL-L preamp and B&W Signature 805 speakers. And also, My VPA has only XLR input and they provided adapters to use single ended input.
Up to now, the performance of VPA is a little fall short of my expectations. therefore I doubt tubes life and want to know how to set the bais.
To "Kleech", please send an email to "firstname.lastname@example.org" regarding setting the bais. I found a black button to the side of the volt meter and 4 screws in the left panel, but I do not know hot to used them to set bais.
Thanks again you guys help and look forward to further information to set bais.