[Elecraft] filter alignment question

[kt5d at charter.net]

I recently acquired K2 #1084 from a friend. I upgraded the radio to Rev. B, added the DSP module and am about half way through the KPA100. As I was aligning the filters I noticed something unexpected. Everything seems to be fine except that as I scroll through the CW XFIL filters, the tone of the test signal changes slightly. Is this to be expected? Is it possible to get the tone exactly the same for every filter setting or is a slight variation normal? 
The DSP was in bypass while alignment on the XFIL filters was done. 

The K2 is a wonderful little radio. It sits on top of an OMNI 6+. Its a tough decision lately which one to use, hi hi.