PX 350 line out noise

[davehertzberg]

Hi all,

 

I recently got a PX 350, and there seems to be a problem with the line out.  The level is fine, I have a plug connected to the headphone jack and the line out is plugged directly into the mixer.  But, there is a horrible buzzing noise that makes this connection unusable.  I am just using a regular 1/4" instrument cable connected to the L/MONO line out jack, directly into the mixer.  Am I using the wrong cable?  Is there something else I should be doing?  

 

Thanks for your help!

[Jokeyman123]

That is not normal obviously.

 

Are you plugging both headphones and line out at the same time-one could be affecting the output of the other. Try cleaning the headphone jack-and the line out jacks-sometimes even a slight connection fault in the jacks might do this. Some compressed air is one way to do it. Or put some isopropyl alcohol or electronic contact cleaner on your plug and insert it into the respective jacks-that way you do not overspray anything inside the PX350. 

 

Have you tried more than one 1/4" cable to eliminate that as the problem? If the cable is shorted inside, it will do this. Make sure you are not using one of the headphones from a smartphone-these have 4 conductors, not just 3 since one is used for the phone mic and could also cause this problem. And if the headphone jack is stuck or shorted inside from dirt or oxidation, it could also cause this.

[davehertzberg]

Thanks Jokeyman...I did try some of these things.  I tried a different cable, and also have tried both with and without the headphone jack plugged up (just with an adapter).  What ended up eliminating the noise was using a preamp direct box (really it's for my bass).  I have the keyboard plugged in through the line out into this box, then an xlr into the mixer.  No noise at all.  So, I have no idea why that works and I'd love to not have to use that box.  But for now it seems to be working.  

 

Any idea why that box would eliminate the noise?