What is the supply HT on an orange bass terror

[mikeydee77]

I have an OBT pre amp board (two 12AX7) that I am planning to use as the basis as a pre-amp project. I can't find a schematic for this anywhere but I need to know what a suitable supply voltage would be. I guess I can estimate a value and experiment but I wondered if anyone that had worked on one of these amps had made any notes on the HT.

Or if there is a schematic out there, please post.

Many thanks Mike