Ecc81 its not the best tube on the first stage, but this is communist time... less everything...if i good remember Polish tube manufecture(...Philips Licence) made the tubes like ecc82-83 but in very small quantities. Ecc81(Ecc82, and Ecc83 too) taken form RFT, and Tesla companies, but Fonia decide to Ecc81...something...
All amplification stages, including the output transformer,
are subject to negative feedback with a value independent of rotary adjustable gain switch...Quotation from Fonia Manual.
I gave the original Fonia TK-15-005 output transformer (very good fraquency response...permalloy EI60 24mm stack), the input Lundahl 7903 ratio1: 8.
Grayhill switch without MBB i think - AJN (N - non shorting if i correctly reading)...my friend testing on the studio, and i don't tell me enything about the pop's on them...