PCM <> NativeDSD on Pro-Ject Pre Box S2


BTW I love 1.4 radio!

Just checking if Roon @brian @support are aware of this (I want to buy the S2):

4th post down gahabana:

“when using S2 DAC in Native DSD mode, when there is switch from 44.1 PCM or 176.4 PCM to DSD64 there is noise that starts about 1-2 seconds into DSD file and disappears after 7-8 seconds”

JohnW (the S2 designer) comes back with the fact that Native DSD works fine on Windows and it must be down to the way Linux switches between PCM and Native DSD, have Roon seen this on ROCK?

Keep up the fantastic work your doing!



ROCK doesn’t have the Native DSD patch for this device yet (the patch is very new), but it will in the future.

We were able to reproduce this symptom on another Linux device that has the patch. The behavior is pretty nasty sounding. The device works fine in DoP mode. That is how I would recommend that you use it, at least until this is resolved.

Based on what we saw here, I don’t think there’s going to be a resolution to this in Linux or in Roon–it seems like the kind of issue that would have to be resolved in the DAC itself. The way Linux treats Native DSD DACs is very consistent from DAC to DAC, whereas on Windows, each DAC has its own driver. There are many XMOS-based DACs working on Linux, and have been for a while, so this seems like it should be technically surmountable.

We ran into a snag trying to get our Pre-Box S2 upgrade to the latest firmware, so our tests were conducted with 2.04. We’re going to follow up with Pro-Ject and see if that can be resolved in case this was fixed in the mean time.

Thanks @brian

Ouch I thought Roon implemented https://github.com/RoPieee/ropieee-kernel/blob/master/usb-dsd-quirks.patch on the ROCK kernel and that shows the Pro-Ject S2 on line 21?

I ordered it yesterday explicitly for native DSD on ROCK.

Will happily upsample everything to DSD but I would really appreciate native.

Native DSD vs DoP has nothing to do with upsampling–it’s just an implementation detail of how the bits are packaged for transmission to the device. Same bits reaching the DAC (and still DSD), just slightly different packaging on the wire.

That link goes into a github repository–so you are looking at the latest version of the patch as it last went into Roopieee. We incorporated an earlier version of the patch (probably, whatever that file looked like as of when @danny discussed it with @spockfish).

We will update it in the future–we do every couple of months to pick up new DACs that have been supported. It’s an ongoing thing for us to keep up with–but I think the DAC issue will remain until it is resolved with Pro-Ject.

Thanks again @brian

Understood on you implementing an earlier patch, look like the S2 was added 11th of November.

@brian can you tell me if the patch to add S2 native DSD has been added to ROCK?

I believe that it has.

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Support for Pre-Box S2 is part of standard Linux kernels, I sent the patch upstream right after I had made and tested it… No need for patches…


I still have the problem in the latest build 1.7 of Roon and latest firmware of 2.12 of the Project Pre box s2.

Running just fine without any problems at all…Can play up 768KHz and Native DSD512…Just fine…all device is on ethernet ( cabled) Cat6a…ROCK to router is Cat8
Chain is: ROCK - ASUS AC87 Router - ALLO Bridge Signature - Project DAC

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