If you are using a tube pre [ I can't imagine why] It will pass DC krell recommends puting some type of DC blocking caps. you can contact Krell for info or your Krell dealer.
When I had my 750 MCX monos several years ago (before I went all tubes) I was using an Audio research Ref 2 Mk ll preamp and never used any DC bypass caps. I had no problems whatsoever.