I have tested this with two DACs (with latest updates):
Mytek Brooklyn DAC+
Marantz HD-AMP1
Mytek Brooklyn DAC+
The problem only exists with the ASIO driver, not the WASAPI driver. When switching from a PCM (44.1) file to a DSF file, there is a brief gap and a pop. Everything is fine in the other direction (DSF -> PCM.) (Interestingly, in previous versions of A+ for Windows the problem was going from a DSF file to a PCM file.)
Marantz HD-AMP1
The problem exists with both the ASIO and the WASAPI divers. When switching from a PCM (44.1) file to a DSF file OR from a DSF file to a PCM (44.1) file there is a gap and a pop. (I believe Marantz uses the standard Steinberg ASIO driver.)
Note that for both these DACs, this issue does not manifest itself when using Roon, foobar2000, or J River Media Center with either the ASIO driver or the WASAPI driver.
How do you play native DSD-dsf in WASAPI mode ?, I think that is not possible.
It’s not clear to me if the Marantz HD-AMP1 supports native DSD or DoP only or both, but for DoP only there is always a switching from PCM to DSD.
My Teac NT-503 supports both, native DSD and DoP playback. But DoP is unusable as the unit first recognizes 176,4kHz PCM and then switching to DSD with a pop/click noise.
Sometimes I do have the impression that when DAC chips switch their internal audio path, PCM to DSD or DSD to PCM, that there is a switching pop when the output is not muted at this time. I don’t know if this mute command should be sent by the driver or by the playback app through the driver or if that is a firmware issue.
Another reason can be some unusual tags, tags are stored at the end, in the DSD-dsf files that will be misinterpreted.
With WASAPI driver, I play dsf files via DSD-DoP. And the Marantz HD-AMP1 supports both native and DoP DSD.
Regarding the switching pop you mention when going from PCM to DSD or DSD to PCM, I have not experienced this with any of my DACs using any other software.
The problem I noted in my original post does not occur when I use JRiver MC, Roon, or HQPlayer. Why is A+ different?