At the Media Center of AMT Electronics user's manuals for AMT Stonehead и AMT PE-120 PowerEater loadbox are available.

Buy now: AMT Stonehead-50-4
http://eshop.amtelectronics.com/guitar-head-and-power-amps-stonehead-tubecakes/amt-stonehead-50-4-guitar-head-amplifier.html

Buy now: AMT Electronics PE (Power Eater) 120 Load Box
http://eshop.amtelectronics.com/loadbox/