Mine has stock Electro Harmonics.Since my Zeus does not have a cover,one day I broke one tube by accident,so I called and talked to Mark.He said to just buy another EH KT88 and re-bias .No need for matching e.t.c.Now if you want to use expensive boutique NOS kt88's since the amp uses 12 power output tubes, be prepared to spend the big bucks.Something to consider I guess.
Best
George
Best
George