I recently downloaded some hires and DSD sample files to test them out (and see if I can hear a difference) and noticed something odd when playing some of them (I'm using an Raspberry Pi 3B running Volumio via USB - WiFi, not Ethernet). I did a search but couldn't find anything on this forum.

The recordings sound perfect - no clicks/pops/dropouts. However, when looking at the Analyzer screen, there are continuous small values on the last 3 bars on the bar graph centered around 16K, increasing linearly, with the last bar peaking at around -50 (the other 2 are lower, all 3 bounce around a bit). Music content doesn't matter; they're always there when playing .dff or .dsf files (I think all are DSD64). I notice that they're also present when playing 32/192 files (2 sample files) but disappear when playing a 32/176.4 files. The RPi is set to play DSD direct and not upsample/downsample files other files. I've used the test files with the RPi, and they show bit-perfect to 32 bits. Also interesting is that the peaks decrease slightly if I use the NOS filter vs the SD Sharp filter.

Anyone else notice this? I don't hear anything since I long ago lost the ability to hear >16kHz, so it's not bothering me. I just want to know if it's a known issue.

BTW the DAC has the latest firmware installed.