DSM-7 won’t support usb connected DACs

There were some discussions on the forum about this a few months back. Lots of users asked Synology for it as a feature request. Their resounding response was a very firm “no, never”…

I imagine it does not help, but here’s what I told a group of 60+ audiophiles at an SFAS event a while back:


Orion OB 3.4’s nice…mine are still at 3.31

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What’s the reasoning behind your opinion that a DAC should’t be connected to a core?

I don’t that today but I can’t see an issue with having a single device (NAS or NUC or Nucleus) doing double duty as a core and, effectively, a streamer. I’m sincerely curious about why you strongly advocate against it.


Mostly because there’s no such thing as a “digital” signal. A USB cable does not have literal one’s and zero’s flowing through it. It’s a complex square(ish) wave with a relatively high bandwidth along with plenty of switching and other analog noise and distortion mixed in. DAC designers do their best to isolate the analog circuits in the DAC from this noise, but reducing upstream noise almost always pays dividends in sound quality.

This is why Roon Labs themselves explicitly recommend separating Core and Outputs by a network connection in their Sound Quality recommendations. I’m not saying that a DAC won’t work when connected via USB to a NAS or general purpose computer running Core, and neither is Roon Labs. But, in cases where sound quality is a priority (eg., a highly resolving system), connecting a DAC to a NAS will never give the best results.

Many find that there is a correlation between lower transport CPU usage (and associated noise) and better sound from a downstream DAC. If you read Roon Lab’s recommendations for how to use their product for best sound quality with this principle in mind, it may make more sense.

Again, you don’t have to do things the way Roon suggests. But, keep in mind that my audience was 60+ audiophiles at a San Francisco Audiophile Society meeting. All of these folks care deeply about getting the best sound quality they can from their setups. If that’s you too, these recommendations are valid.

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What is the difference since most of the end points are just another computer (more or less)? Or to be more specific:

What makes this …
Core (computer) → Network → EndPoint (transport or whatever it’s called these days, but still a computer) → USB → DAC
… better than this?
Core (computer) → USB → DAC
(assuming all the hardware above is in the same league).

Roon Labs explains it this way in their guide to Sound Quality (link above):

To get the best sound quality from Roon, plan for an ethernet cable between your Core and Output components. One way to accomplish this is with a Roon Ready hardware device.

Our lightweight playback components (Roon Bridge, Roon Ready devices, and networked endpoints) are much lighter than any media player software out there because all they do is copy audio from a network interface to an audio device. They don’t even have to do work to decode your media files!

These small, fanless, solid-state, low-power devices generate and transmit less RFI, EMI, mechanical vibrations, and acoustic noise than a computer thats powerful enough to run Roon Core or the desktop app.

Roon’s distributed topology leverages the inverse-square law to enable better sound if you want it. And, generally, it’s not very expensive to deploy this topology; endpoint devices starting at under $100 (some assembly required, eg., RoPieee and VitOS) and very nice ones, like the ZEN Stream from iFi audio being only a few hundred dollars.

I don’t buy it (my problem), but thanks any way.

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Sure. I figure that Roon Labs knows how their system works and how to get the best sound out if it, so I followed their recommendations. I’m convinced that I’m getting better results, and I’ve not looked back. No harm if for some folks this topic is not worth the effort to explore.

Thanks, @David_Snyder. Not the response I expected but I appreciate you clarifying.

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I highly recommend installing ROCK on an Intel NUC (any supported model with i7 processor can be bought cheap on the 2nd hand market and will give you a much better experience for years). You will get option to connect external DAC via USB, even though it is preferred to use a Roon Ready endpoint for optimal experience and audio quality.


For what it’s worth. I kindly like to share my latest experience about the subject of this topic.

Many years now I am using a Synology DiskStation with running Roon Core on it and with DiskStation’s USB port connected to my Lyngdorf amplifier (with a USB module build in). Until now I was very happy with it.

Because of the coming release of DSM7 (and the end off USB DAC support) I searched for an other solution. Therefore I bought an Raspberry Pi 4 as endpoint, installed VitOS on it, connected it to my local network via a ethernet cable and lastly connected it via a USB cable to my Lyngdorf. After installing Roon Bridge in VitOS (with the special VitOS Manager app on my iPhone) Roon Core on the Synology found the new Raspberry endpoint immediately.

Now my experience with the sound quality in the new setup: the result is unbelievable. With the Raspberry the sound is clearer, much more detailed in high, mid and low and the sound image is far better in 2D as well as 3D.

To me this proves that RoonLabs is very right with recommending not to put the Roon Core and the Output on the same device. Or in the words of David Snyder: “Never, ever connect a USB DAC directly to a Roon Core device”. :wink: RoonLabs (@danny) and David Snyder (@David_Snyder) thanks for the recommendation.


So I am intending to get the fanless QNAP 435-DX NAS, is it better to have just SSDs instead of a HDD / SSD hybrid solution?

If you plan to run the core on it, then fully SSD would be the route to choose. The hybrid setup uses the M.2 SSDs for caching. You’d still need an SSD for the database.

Also, I’d ask around as to whether the CPU is powerful enough for Roon - it’s below the minimum recommended spec.

Currently using a HS-251+ which is powered even lower. Though my local databases isn’t that big and mostly stream via Qobuz & Tidal.
Right now the database is on a 128GB external SSD connected via USB 3.0
Would that also be something recommended or going fully SSD? The hybrid approaching would be nice to have for local movie storage / streaming.shouldn’t it be possible to assign some of the M.2 connected SSD space as database location as well as local FLAC files?

If your current NAS works for you, then the 435-DX should be fine. Yes, you could run the database on a USB 3.0 SSD and use HDDs internally.

It’s a straight forward process to migrate your database to our new NAS too.

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It’s up to you to setup the internal storage (2 x M2 and 2 x 3.5"/2.5" all SATA) and use as you like it. There is no need to use anything for caching. Also IMO if you want a silent system put SSDs instead of HDDs in the drive bays. Generally IMO but especially if you want to use HDDs buy models listed as compatible:

Note: To avoid excess vibration and heat generation, it is recommended to use 5400 RPM hard drives or low-temperature/low-noise NAS hard drives with the HS-453DX. Check compatibility list.


From my reading of the details for the QNAP 435-DX, I thought the M.2 slots were only available for read/write caching. Thanks for your helpful insight.

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Synology ones are cache only IIRC