ADA Preamps > MP-2

Noise and feedback

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rickeb1:
I am having a terrible noise problem with my MP-2 setup, and I'm not sure what to do about it.  As detailed in another thread, I initially had some issues with the unit, and sent it off to JMP, who fixed whatever needed fixing and sent it back to me in perfect working order.  This past year, I moved from the Chicago area to Phoenix but kept a home in Illinois as we plan to come back to visit friends and family often.  I wanted to put together a small second rig to use in Illinois for jamming with friends while I'm there, so I wrapped the MP-2 in a lot of bubble wrap, stashed it between clothes in my suitcase, and took it with me when we flew from Phoenix to Chicago this week. 

When I pulled out the MP-2 and hooked it up to a power amp and speakers, I started getting this dreadful noise and feedback from it.  Note that this is only on high-gain settings; clean settings and even voice 5 seem to work ok.  The gate helps some, but on some high-gain settings, there is a huge midrange feedback.  Without the gate on, you can also hear some motorboat oscillating.  Not sure of the frequency of the feedback, but it's more midrange than high-pitched, I'd say it's around C played on the second string, and very full and bassy. 

I thought at first that a tube had gone bad during the travels, so I replaced the tubes, but nothing changed.  Then I thought that maybe the guitar (a Schecter C1 Blackjack that I picked up cheap as a second guitar), which has active pickups, needed a battery replacement, but that didn't help. either.

The odd thing is, sometimes the noise goes away, but then if I move, it starts up.  Also, if I turn the volume of the guitar pickup down a bit, it stops (or the gate covers it).  I started thinking maybe a bad guitar cable, but you'd think I'd hear that on other voicings, not just the high-gain ones.  Or maybe a ground or shielding problem with the guitar, but again, you'd think I'd hear it on other voicings.

I guess I don't want to believe there is an issue with the MP-2, as it was working fine before I transported it from Phoenix to Chicago, and it will likely be the most difficult to fix. :(

Anyway, given all that, does anyone have any thoughts as to what the problem might be and where I should begin in trying to fix it?

~Rick

MarshallJMP:
Does this happen when nothing is plugged in into the mp-2 (input)?

rickeb1:
No, with nothing plugged into the MP-2, it is dead quiet, no matter the setting.

MarshallJMP:
Then i think it's something outside the mp-2,cable maybe?? If it was the mp-2 it would also do it with nothing plugged in.

rickeb1:
Thank you so much for the quick responses!  That's actually good news, as it narrows things down to things I can more easily address.  I will find a different cable and go from there.  Thank you so much JMP, as always, for your help!

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