welcome to the forums!
one reason for a different sound on the eight assignable outputs can be the fact that the internal effects only work on the main stereo outs - so if you use any effect on your kick then that might be missing now.
you can either leave the sample with effects on the main outs and move other sounds to the assignable outs to spread them out, or you can resample the sample with the effects to a new pad and then route this "wet" pad to one of the assignable outs.
another reason for the different sound can be the difference between stereo sound thru the main outs and mono sound thru the assignable outs - you can change this by not using a single assignable out, but a pair of them e.g. 12 or 34 etc.
peace, jo
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