Shreddage 2 SRP - Noise at the end of sustained notes?

[howard17]

Hi,

in SRP, when playing a single sustained note until the very end of the sample - when the tone of the string is getting quieter I hear some sort of digital sounding buzzing noise setting in. Even when listening to the dry signal it is clearly audible with headphones and it's worse with distortion, of course.
I can not hear the noise in the Shreddage 2 samples, only in SRP.

Does anybody know what that noise could be? Could it be related to the pickups used in the different guitars?

As I rarely need this extremely long sustained notes, the noise isn't really notable during normal playing. I'm just curious to know where it might come from as it doesn't sound like standard pickup noise to me.