Info wanted on George Wright AU-1000 12BH7 preamp

I bought a used George Wright AU-1000 preamp with tone controls off of Audiogon. It is an excellent sounding preamp in my opinion. It uses 3-12BH7 tubes, 1-6BM8 tube & 1-6x4 tube. Uses Auricap capacitors & silver point to point wiring. Came with a set of 3 Tung Sol 12BH7 tubes, a set of Sylvania 12BH7 tubes, 1 Sovtek 6BM8 tube & 1 Sylvania 6X4 tube rectifer. The AU series of Wright gear is an upscale line sold in Audio stores and not direct from Wright Sound. I emailed George Wright with questions 2 weeks ago-no response. Does anyone know what circuit is used-cathode follower or SRPP. Specs. NOS tubes to use that will bring optimal sonics. The high/low switch on the back for volume control, can this be switched with the preamp on?
I own a used Wright Sound WLA12A and have corresponded with George a number of times. He is sometimes slow to reply due to his being a very small business, but he is always courteous and helpful when he finds the time. Here's the address I use:

I wouldn't be afraid to email him again - I've had to contact him twice occasionally before he answered, but he never seemed annoyed. Good luck!