[Elecraft] k2dsp operation

[Karin Johnson]

Hi All:
I've a question about the operation of the DSP unit
in the K2.  When setting the C1 filter to Lowpass
by following the proceedure in the manual, I get NO
audio from the receiver with the display set as
C1 LPASS.  Note the capital C in the beginning
of the display.  If I set the "C" to lower case "c"
I now get audio from the receiver.  This is an unusal
type of operation if I understand the process of the 
DSP correctly.  I have the radio set to the widest 
IF filter setting of 1.5 KHz and have the receiver
tuned to a signal generator producing a tone of
about 500 Hz audio.  I am also looking at the audio
output on an audio spectrum analyzer to confirm the
presence of background noise and audio signal.
I've not tried the same experiment on SSB, only CW 
mode so far.  Is this "normal" operation or am I missing
something in reading the instruction manual?
One other thing which may or may not be related.
If I have the "C" set indicating the more severe type of filtering
and then also have LPASS set, where I get no audio from the
receiver as above, if I then decrease the center frequency of the filter
from the LPASS setting downward, as soon as I get to 
400 Hz for the bandpass center frequency then audio appears
from the receiver.  The bandwidth setting always remains
at the widest at 800 Hz.  Any thoughts from the group
would be appreciated.  I'm trying to become more
familiar with the operation of the DSP and so far everything
else looks fine.

               Regards,
                  Karin Anne Johnson   K3UU