[Elecraft] 250hz Filter - Audio drops

[Tommy Alderman]

This is driving me crazier!
My narrow filter is 250hz (FL4). FL4 cuts in when I change my DSP filtering
to 250 hz, as it should. FL4 stays in as I make DSP more narrow, all the way
to 50 hz. 
The problem is that when I change DSP from 150hz to 100hz or to 50hz, my
audio output seems to drop tremendously, to the point I have to increase the
AF gain to hear the intended signal. The audio does not come back to
'normal' level until I change DSP from above 100hz bandwidth.
I have FL4 set for 2dB gain; FL4 FRQ set to 0.00.
Would appreciate any suggestions to fix this as I hope it is not 'normal'
operation?
Tom - W4BQF