Vintage Simmons Drums (UK) Users Group

Hi, I am new in this group so hello to everyone :)

I recently bought a black sds9 5 piece set in a simmons rack, sds9
module and manual in english :)

I am very satisfied with it, but have one little "problem". I get some
background noise (static?) from the Headphone output. What could cause
this? 

Thanx