WiiM Mini Distortion, both optical and line out

[Drmevo]

I have a strange issue I just discovered, hope someone can help. My set up is currently WiiM Mini, optical out to Parasound NewClassic 200 Pre, to Aiyima A07 Max, to Kef LS 50 Metas. I also have a Yamaha AVR hooked up for HT bypass. This is is happening with AirPlay streamed from Apple Music.

I just got the Aiyima and while playing around with different levels, I noticed some strange distortion in the guitar intro of “Plastic” by Moses Sumney. It’s almost a faint scratchy, fluttery sound like a dirty pot on a vintage amp, and the distortion occurs when the louder guitar chords are strummed.

At first I thought it was the amp, then I tried the same song using my Yamaha AVR as the AirPlay source with the Parasound in Bypass mode and the distortion was gone. Also no distortion through my decent headphones, so I know it’s not the song.

Maybe the Parasound DAC was the issue, I thought, so I tried Line Out from the WiiM into an analog input on the Parasound. Same distortion. Next step was to rule out something with the preamp itself on the Parasound, so I tried the WiiM into the Yamaha first via optical and then to the Parasound in Bypass mode. The distortion was still there.

All of this tells me that the WiiM is the source of the distortion. But my EQ is off, volume is set to fixed. I don’t know what else could cause it, but it’s repeatable and it happens no matter the volume.

Any ideas what could be causing this?

 

[Drmevo]

I found the issue - it was EQ after all! I thought I had updated the app, but apparently just the firmware was up-to-date. After the app update, it showed EQ was On. I had messed around with it about a month ago and decided to turn it off. Except, apparently, it didn’t turn off, even though it displayed that it was off. Following the update, toggling it off cleared up the distortion.

It’s probably old news to many on here, but I would advise against using EQ with the Mini, at least parametric EQ, to avoid adding distortion.