I leave it in there most the time, but to reduce the amount of noise, there are a few things you can do without a computer.. the results are not as good, but good enough for me.
First, make sure the record is clean.. if all it takes to reduce the amount of noise is some alcohol and a rag, do it.. don't put that hen-dog (hennessey to those that don't know) you have under your bed on the wax tho

Before you start sampling adjust the turntable mixers eq's a little.
Secondly, turn the record level down as much as possible, and watch the level of the sound coming from your turntable mixer.. if it's constantly hitting the red mark, turn it down a lil.. if the wax is already dirty, then sampling it too loud will just create more noise /hum/nice crispy cracklez.
Third, adjust the low-pass filter in the mpc from 100 down to 90 or 80.. play with it a little.. think of the lowpass as bass, and the resolution as treble.. I know that's not what it is, but if you increase the resolution on a sample with lots of crackle, it's going to really stand out.. adjust the filter, and it 'somewhat' lessens the amount of hiss/pops.
And the last thing I do is adjust the EQ on the mixer. If you reduce the amount of High's in the sample (to lower the amount of hiss/pops, you may be able to bring some of it back on the mixer. When you do this, the noise you don't want won't be there, and you'l have that sound you were trying to get without spending any more money. If you do have a computer, then that would probably be a lot easier.. but you still have to shift the sample from one machine to another.. either way, it's gonna take a lil work.
. ..dyrtrax. ..