Hi Cassp
When you compare the note played on the keyboard with the same note played on the pedals, do you make sure that dynamics (Velocity) and after touch (Pressure) is turned off on the keyboard, as if not the sounds produced will be totally different. (The PK7 as you say is just full on, full off)
If the above is the case then you will need to purchase a dynamic pedalboard, (As far as I am aware there has not been a pedalbord made with after touch) that will give you a closer sound to the notes played on the keyboard.
Hope this helps

Bill

Sorry, Diki

I confused your post with an earlier on from chas. Thanks for all the help you give to the SZ.

Many bass pedal sets allow you to set the velocity level yourself. If, for some reason, it gets sent as a 127, well, that's going to make just about ANY keyboard bass sound sound different unless you are banging the bejesus out of it!

Dial it down to maybe 100 or so, and it may start to sound a bit more like the keyboard version of the sound.