I bought a Gustard X16 and it has the popping sound between songs when playing DSD files. PCM files has no issues. I use the latest version of the USB update from the Gustard website, but I don’t own a programmer so the firmware is original. I listen to DSD on foobar2000 via USB and sound quality is excellent.
With headphones it is more like a quick «tick!», maybe because my AKG K-271 headphones don’t have any bass, but with my horn speakers and subwoofers, it becomes a very apparent «Pop!» It also has some scratchy sound around the same time, during the quiet period in between songs.
I contacted Audiophonics.fr and we agreed to send the unit for service under warranty. So far, a very smooth experience.
I noticed it most on the album Pink Floyd - Wish you were here, and Roxy Music - Avalon. Less so on Michael Jackson - Thriller, but it is still there.
I read an article saying it has something to do with when the DAC is checking and sometimes switching between file format for the next song. I also found this answer by Jussi in the Roonlabs forum:
«The specification requires DAC to mute output for 50 ms when DSD stream is starting and when it is ending to avoid such noises.»
So it is up the manufacturer to dampen the noise in the DAC. Apparently Gustard did not do this in the firmware version 0.01. Hopefully a firmware update will resolve the issue.
This should be an obligatory test for all DACs in the future, because it is not fun to listen to pops, ticks, and scratchy noises, when the point of listening to DSD files is to have the best possible music experience. The more I read it seems a few other DACs has this problem. When you first notice it you hear it all the time. It reminds me of the Pringles potato chips commercial: ONCE YOU POP, YOU CAN’T STOP!
To not follow DSD file specifications is pretty serious! I am surprised it does not get more attention on a site like ASR where distortion is measured down to 0.000001%.