hi,i got different sound output from bridge and neck pickup.the bridge pick up have less output than the neck.i raises the pick up but nothing changed. the difference in the voloume is high especially in the d and g string.the instrument is a mk standard.what can i do?

You can try adjusting the trip pots inside to change the volume output from each of the pre-amps for the neck and bridge pickups in the bass.
 
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Jazzyvee

Also, you might try 'leveling' your pickups:
 
If you're hotter on the D & G strings, look and see if the pickups are 'up' on that side.  I usually take a small ruler and raise/lower the pickups until they're the same distance below the E side and the G side, to give me a starting reference point.  Then, adjust as you like if it's boomy or weak on one side or the other to your ears.
 
Between that adjustment and the trim pots, with a little tweaking you should be able to dial in exactly what you're after.  As always, it's better to do this with new strings:  When it comes to fine-tuning, you can't trust what old strings are saying.
 
J o e y