DSD 256 on Mac Mini

I am running Roon Core on a QNAP NAS, feeding a Mac Mini (client) which, in turn, feeds a Playback Designs MPD-8 DAC (the Dream DAC). The DAC goes up to DSD 256 (according to the spec sheet). However, when playing, the DSD 256 files get converted to DSD128.

When I go into the Roon setup settings for the DAC, the maximum DSD resolution available is 128. Which I is why I presume this is converted down.

Is the problem with the Mini / OSX? Is it a problem with Roon? or with the Playback Designs DAC? Is it a limitation of DSD over PCM? If so, any way to go directly?

It is a limitation of OSX and to Linux. Windows is a driver led system so the correct drivers will allow full functionality assuming your hardware is capable. OSX and Linux relies on generic class 2 audio functionality which tops out at DSD 128 DOP. You can have drivers or patches written to get around this so some hardware can function at full capability if the manufacturer or an enthusiast has done the work to make this possible. To summarise this is an issue between the DAC and operating system of the end point.

Thanks. Is that an inherent (built-in) problem in the OSX or can this be addressed in future versions of OSX ?

Apart from using a Windows machine to get around the problem, what other solutions would I have to feed the DAC with DSD256?

It inherent to macos and Linux. Not a lot you can do the manufacturers don’t seem to bother to produce drivers themselves to rectify the issue and support their DACs on windows. Some Linux distros for audio often have wider support or if you ask will create one. When I was using my Allo USBridge which runs Diet.Pi and os for arm processors my dac would not do native dsd only dop, so one of the Allo team compiled a drive to give me the functionality.

It looks like the Sonore Rendu products will allow full capability. Certainly one review of that DAC said they used an optimised Windows PC :cry:and the Sonore SignatureRendu as endpoints to realise DSD 256 native.

Ropieee on RaspberryPi might also be an options for RoonBridge - @spockfish Harry might be able to let you know if this DAC is supported in his RoPieee builds

To be more precise: it’s not a limitation nor is DSD limited to DSD128 on Linux.
What happens is that your DAC is not recognized doing DSD natively, hence it switches to DoP. As this means the DSD information is being packaged in PCM information it uses more bandwidth, hence that with DoP it’s max rate is lower than doing DSD natively.

The advantage of Linux over MacOS is that this is something that can be patched into the kernel (while on MacOS you’re dependent on Apple). But it also requires the DAC to ‘behave’ properly and providing the right information to the OS to be able to do native DSD.

Do you have a Linux machine nearby? We can then at least ‘have a look’ and see if this DAC is capable of doing native DSD at all.

Hi Harry,

The DAC does DSD natively, definitely. Andrea Koch is one of the main guys in DSD - he designed the Sonoma DSD decoder that is used by many studios. I do not have access to a Linux machine unfortunately. i know that the DAC will run DSD natively from a PC using a Windows OS.

Yeah, but that’s not what I meant.
Of course the DAC does DSD natively, but on Windows it uses a specific driver for that.
I’m curious how it behaves on Linux to see if we can make it work over there as well.