@Ludwig is correct, DSD128 turns into a 352.8kHz PCM signal, and Roon is detecting that the DAC can’t accept that and converting to PCM instead.
Is Roon capable of converting from DSD128 to DSD64?
Resampling DSD->DSD is not straightforward, and frequently involves a conversion to PCM as an intermediate step anyways.
The only time I would want a DSD->DSD downconversion is if I were driving an SDM DAC (not Meridian), and I had enough CPU, and a good DSP implementation. (aside: this is the sort of thing that HQPlayer does well, and virtually no other software out there attempts this sort of thing).
@brian can you clarify this confusing situation please? And can you perhaps force the correct settings - and just one output - when an 818v3 USB input is connected?
A well-behaved device should connect via USB Audio 2.0, and might expose itself via one or two drivers: a WDM (Windows Driver Model) driver is almost always present, and often an ASIO driver is, too.
Well-behaved ASIO drivers should support receiving DSD in native mode if the device supports DSD at all (it sounds like Meridian may have skipped this step). dCS mode is there for people with early DACs made by dCS that pre-date the DoP standard.
All drivers are provided by the manufacturer in this case–Microsoft does not ship USB Audio 2.0 drivers, nor ASIO drivers. The Meridian package contains one of each.
The choice to use ASIO or WDM drivers is yours to make. Some people believe that one sounds better than the others. Assuming the driver vendor has done their job well, they should result in the same bits on the other side of the pipe, so if you believe in bits=bits, the distinction will seem pedantic and unnecessary. But many people don’t believe that and would consider Roon to be an incomplete product if we didn’t offer both options.
Do you recommend using ASIO when available?
I think Microsoft did a good job with WASAPI and that alternative driver stacks like ASIO are for the most part an unnecessary evil in 2015.
There are some wrinkles, however…
- Native DSD–when a DAC supports it, ASIO drivers can enable direct transmission of DSD data without encapsulation.
- Some USB interfaces expose a non-bit-perfect volume control via their WDM drivers. You can tell you have one of these if DSD sounds like a hiss at <100% volume. If you have one of these, disable Roon’s volume control (which is just tweaking the WDM volume controls under the hood).
- Some manufacturers do a better job on one driver or the other. Sometimes the drivers talk to the card very differently and can expose different hardware behavior. Fragmentation is sloppy.
- Manufacturers are chronically terrible at exposing accurate descriptive strings for their devices, and often make weirdly inconsistent choices between their ASIO and WDM drivers, and this can make the settings/configuration experience more confusing than it needs to be.
ASIO is an option to try to solve a problem with a bad WDM driver, but I always start with the non-ASIO option first.
Should surely be possible to make this just work without user fiddling necessary.
We have discussed doing an “auto-setup” feature where we work with device manufacturers to build a database of devices + recommended settings, certify devices one by one as working properly with those settings, and then have Roon recognize them and set things up reasonably well by default. I think that would accomplish what you are looking for, but it’s a big project that requires visiting devices one at a time, and not something we are inclined to do for a single piece of gear before there’s a process in place for covering a wide range of products from different vendors.