I agree with @mlsstl. Borrow another preamp and see if the problem goes away. I was a fan of old Krell myself. They need recapping every 7 to 10 years or sooner depending upon use. Regardless of your problem, if you never recapped it, have it done. Krell in Orange, CT used to service my 97 vintage models. Better is the site below. They will use better parts do a meticulous job IMHO. Insane waiting times to schedule repairs with both.
https://www.theservicedepartmentct.com.
Krell Service - speakers buzzing
I recently started experiencing a buzz in both my main speakers, After lots of troubleshooting, I believe the issue is my pre-amp. When the pre-amp is on or off/stand-by, the buzz is there. When actually unplugged, the buzz goes away. It is a Krell KAV-250p. I bought it used in 2013. My questions:
1. Why is it causing buzzing? I am more curious than anything.
2. Is there any point in trying to replace the cables between the preamp and amp (XLR type)? When I unhooked them the buzzing went away, presumably because there was no longer a connection between the pre-amp and amp. My assumption was since both speakers are buzzing, that is not the answer.
3. If you all think the pre-amp is the issue (and there is nothing else I should try in terms of troubleshooting), can it be serviced? Is it worth servicing? I like it. On the other hand, always fun to upgrade a piece of equipment, except everyone tells me the KAV-250p is a good unit.
Let me know if there are any other details I can provide. Thank you.
Jeffrey