Is PCM to DSD always DoP?

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Hello. I’m trying to wrap my mind around PCM to DSD upsampling and wondering if my DAC has issues or I need a special USB cable…

I am streaming Tidal using Roon server and HQP on my mac mini. It’s connected by USB cable (tried a couple) to a moon 280d DAC. The Moon Dac says it takes up to 384 PCM and 256 DSD native. The highest rate the DAC will register on it’s display is DSD128 or 384PCM despite having all the settings in HQP at 256DSD. It is the same when I try upsampling with Roon DSP as well.

I’ve tried to piece together the reason from various posts and I’m guessing my problem is that upsampled PCM must be transmitted by DoP and requires 768 PCM whiich exceeds the DAC’s 384 maximum.

Can anyone confirm my guess and, if so, is DoP the only way to transmit PCM to DSD upsampled materal?

Thanks in advance!

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Hi @donald_garrett,

The MOON 280D only supports DSD256 on Windows as a special driver is required for “native DSD” support and that driver is only available for Windows (or a highly patched linux kernel). Simaudio’s documentation isn’t especially clear on this and that has led to a lot of confusion.

As far as I know no one has released an OS X driver that supports native DSD for the XMOS USB chipset that most of the industry uses.

This is partially correct in that this isn’t specifically a requirement for upsampled PCM, it’s a limitation in how DSD256 must be transmitted. In order for DSD256 to be transmitted via DoP it needs a PCM sample rate of 705.6KHz as the carrier. Very few DACs support this which requires a special driver that sends the raw DSD bitstream at its native rate.

If you want to do DSD256 into the 280D you’ll either need a windows endpoint running NAA or one of the linux-based endpoints that include USB and NAA support.

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Only if the DAC is supported for Native DSD by the particular linux endpoint. That list is pretty thin right now.

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I’ll admit that I haven’t looked into this recently, but I thought that support was more tied to the specific XMOS chipset rather than the specific DAC. Since there aren’t that many variants of the XMOS chips I figured that support was a bit wider. Very good to know!

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You’re right it is related the the specific XMOS chipset but it doesn’t necessarily mean the particular device ID has been added by the linux appliance vendor.

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Excellent! Much appreciate the very prompt education. I guess I can quit beating this dead horse :slight_smile:

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If you want to do DSD256 into the 280D you’ll either need a windows endpoint running NAA or one of the linux-based endpoints that include USB and NAA support.
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Would the DAC recognize native DSD256 files I have on my hard drive as DSD256 or is this specifically for upsampled PCM to DSD256?

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This applies to all DSD256 data regardless of whether it’s a DSD256 file or some other format upsampled to DSD256.

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I don’t know if you have the MiND module for your 280D, but if you do (or would consider getting one), you might want to ask SimAudio if they have any plans for Roon integration. A RoonReady MiND module could be a great solution for you.