What circuit is the amp based on mate, it sounds awesome :D
12AX7, GZ34 and KT66 I'd say sounds like a recipe for a JTM45-inspired amp.
You are spot on!
it´s my own design based around the mighty JTM45/59 bassman circuit.
Specs:
- JTM45 ( 5F6-A ) inspired amp with a couple of Plexi era twists
- Built to my specs by the same guy who builds the amps for Carl Martin
- Hand wired using terminal strips a là Hiwatt
- Combination of TAD Mustard, Sozo and Auricaps coupling caps
- Valves; 2 x KT66 GEC, 2 x Mullard ECC83, 1 Philips ECC83 with matched triodes for the PI, 1 x Philips GZ34. Naturally all NOS .
- Parallel FX loop with mixing pot and gain reduction switch
- Cathode bias operation switch
- Master volume pot
- Custom wound Power transformer and Obsolete Electronics JTM45 repro output transformer wired for 16 ohms.
- Black Tolex covered
- 2 x 12” semi-closed cabinet, same tolex as head with handles a là vintage VOX + BluesBreaker grille cloth.
- Weber Blue Dog and Silver Bell alnico speakers. 12”.

Love a couple of these glowing inside

This amp sounds great with Fenders but with Gibsons (even with P90s) it is the bees knees...really ;)