Good news to engineers:
Some time ago, a AC member ask info about various secondary winding output trafos.
This week I find it, in this Russian SPB-Sound site(not english version though), where there is various GM70 and GU48/833A amps with two and three ways output secondary.
Surely a curious feature, there is a taste for everything nowadays:
Power Amps:
http://spbsound.narod.ru/SPbSound/photo/usilmoz.html833A with 3 ways iron:
http://spbsound.narod.ru/SPbSound/schematic/schematic2.htmlUnfortunately all amps use interstage iron, no price info or underside photos too.
Regards