Thank you both for your help. I’ve now resolved this on my end, but I thought I’d document that just to close the loop.
What happens if you bypass HQPlayer entirely and have Roon play directly to the DAC, do you notice any of the slowdowns in playback starting? Does the slowdown affect multiple zones or just that one DAC? Have you tried to simplify the HQPlayer filters?
Bypassing HQPlayer or playing directly from the Mac mini without the NAA both solve the issue; simplifying the filters made it less-bad. All of these are viable solutions to this specific issue, and I was already aware of them, but it’s not what I wanted to achieve. The Mac mini wasn’t stuttering with the upscaling and filters which I was using, it was just the hardware delay.
HQPlayer offers a hardware delay up to 250ms, but this was not enough for me when using a full length buffer.
Resync delay is mostly applicable when Roon switches between different sample rates. The idea behind the test Daniel mentioned is to have Roon upsample everything to one sample rate, so that Resync delay is not a factor.
I did confirm that on the latest build 1510, when switching between sample rates, the resync delay was applied. A 10000ms delay would lead to around 10s of silence before each new song and there was then no cut-off when the music started. This only worked when switching sample rates, though, which also is not what I wanted, since most of my music is 44.2 kHz PCM.
I cannot confirm the previous behaviour without an installer, which you won’t provide. I am convinced that I was not previously having this issue, but I also clearly didn’t understand the resync delay functionality, and I don’t see how that would have solved this issue for me on the previous build.
Ultimately, I need the NAA because Mac OS doesn’t provide the drivers for Native DSD, and because the Mac mini has no earth on the C7 cable, so I was hearing hum on the DAC when connected over USB. My particular DAC (a Sony TA-ZH1ES) also doesn’t have an earth either, in spite of using a C13 cable. I have it earthed through one of the RCA ports, but I still hear a faint hum when connected directly to the Mac mini.
Neither HQPlayer nor Roon supported the delays I needed. The delay was necessary due to the size of the buffer. Using a shorter buffer from HQPlayer would solve the cut-off, but it would also cause the music to stutter if there were other network requests passing over the WiFi. My router can only handle so many simultaneous connections. The solution was to run ethernet to a switch and hardwire it all together. I had hoped to avoid this as the ethernet run is messy, but it appears to be the only way.
Thank you again for your efforts.