No I can't say it's a gain issue definitively but it might be. Gain may be adjustable internally which is the case with mine. Call Krell and ask them if they have any insight and if the gain is adjustable and try it.
I would be asking myself a few additional questions: Has it always done this? Did my old equipment hiss? When did I first notice it? Did anything change that might have caused it? Is it definitely the amp (i.e. turn everything else off, try different cables, single ended, balanced, speakers, etc.- borrow them from a store or a friend)? If it is definitely the amp and it's not affected by cables or speakers then I'd be talking to Krell.
I would be asking myself a few additional questions: Has it always done this? Did my old equipment hiss? When did I first notice it? Did anything change that might have caused it? Is it definitely the amp (i.e. turn everything else off, try different cables, single ended, balanced, speakers, etc.- borrow them from a store or a friend)? If it is definitely the amp and it's not affected by cables or speakers then I'd be talking to Krell.