Cleaning dirty kick samples

Here is a good way to extract and clean up a kick from a loop.
To do this you will need a sample player with a low pass filter and modulation capabilities including an LFO or Envelope which you can assign to the filter. Good examples would be either logics EXS24 or Halion in Cubase.
Click to hear the example I have used to show how the kick can be cleaned and tidied up for use in your own track.
As you can hear, there is a fair amount of noise included after the initial hit. Fair enough if you want to keep this but to get rid of it you will have to do the following:

Firstly, assign a low pass filter to the kick and listen to the sound when you bring the cutoff down. This will give you an idea of how much bass there is etc...
Adjust the cutoff until you can't hear any of the unwanted elements and then assign an Envelope to the cutoff frequency with a value of approx 75-100%.
Then go to the Envelope and adjust it with the following settings:
Attack - 0
Decay - 50%
Sustain - 0

Release - 0
To get the kick sounding just right you will have to reduce the decay until it is closing down the filter quick enough to cut out the unwanted noise.

Play around with the value of the envelope assigned to the cutoff to decide where the filter starts from before it is reduced. Sometimes, if there is a hi hat on the beat then a lower setting may be better.

Click to hear the same sample now cleaned up with this method.
An other way to get similar results is with an LFO instead of an Envelope or even a combination of the two when particuarly tricky loops are being worked with.