Krell KSA-250 Rev. B?

Never heard of it. The prior marks of Krells
(KSA 80 and 200) initially were only single-ended, and there's a -B version of them to indicate a balanced input on the later versions, but I thought all the KSA-250s had both balanced and single-ended inputs. You might call Krell, they're good about this--maybe it relates to a factory upgrade?

I could be wrong but I think the ksa was changed to stay in class A mode to a higher output. I think the rear of it is layed out like the ksa-300 also.