Buzzing noise from acoustic guitar when connected to amp

[Justinian]

I noticed recently that one my guitars is getting buzzing noise when connected to acoustic amp (mostly upper strings…E, A, D).
My buddy re-installed new Fishman pickup, checked all connections, inspected guitar from inside and couldn’t find anything unusual or damaged.
I tested same guitar with Seymour Duncan (Woody) soundhole pickup and it was working perfectly fine (same as unplugged).
As a test my other acoustic guitars are working fine on same acoustic amp.
Any idea what can cause this sudden buzz issue?

[jseth]

A bit more information would help... what sort of buzzing are we talking about? What Fishman pickup was installed? Is the sound vibrational or electronic?

Obviously, the "weak link" is the new pickup that was installed... frequently, the wires that lead from the pickup to the output (or to the internal preamp) can rest on the back or top, touching just enough to cause a weird buzzing on certain notes or certain strings.

Sometimes you can get an idea of this by holding the guitar in various positions while hitting the offending note(s); just changing the position can be enough to get it to stop or to make it worse - letting you know that it is a vibration coming from one of the wires. It's not a certainty, but a good indicator.

[Justinian]

The pickup is called “Colour name: Fishman 301” and it replaced old one when I noticed first symptoms of buzzing (same pickup model which was working fine for a years).
With old pick it started buzzing on string A and it was spreading to E and D.
Unless new pickup is defective it’s hard to find logical explanation why it’s not working properly. I would assume that was installed properly because my buddy did it numerous times on different guitars and they are all working fine.