Issue with Graininess from my Aurender N100H

I've been using an Aurender N100H for the past 3 months for digital streaming (TIdal HiFi) and my digital library (AIFF, ALAC, Hi-Res files on the internal SSD drive).  Overall, the sound is outstanding with good soundstage, serious detail, rich timbre, etc.  However, much of the music has a "coating" of graininess or static.  When the system is not playing a track it is silent, but during songs, especially, quieter passages, the static is more pronounced.  It happens on both the internal drive tracks and streaming via ethernet.  It seems to be more pronounced while listening to horns - alto and tenor sax and trumpets.

I have tweaked the system by switching out the stock power cable with a Shunyata cable plugged directly into the wall versus the Venom.  I have run the Curious USB cable directly to my Multi-bit Gumby and also through an ISO Regen with an Ultracap LPS-1.  I just picked up a Schiit Eitr SP/DIF converter and have a Kimbler D-60 going to the optical.  In each case, I get the same graininess.

Anyone have a similar issue.  Remedies?  Thanks.