Roon Bridge on bare RPi 2B feeding asynchronous USB-DAC -> feasible or not?

My personal audio zoo comprises a Pioneer SC-LX87 AV-Receiver which has an asynchronous USB-DAC input supporting 192 kHz/32 bit PCM content or DSD64 via DoP.

Will RoonBridge be smart enough to support any USB interface on the Raspberry Pi 2B in such a way that it can feed the USB-DAC flawlessly up to 24/192 resp. 24/176 in case of DoP?
By “flawlessly” I mean (a) no glitches due to insufficient processing power, (b) no glitches due to too much Jitter on the USB line, © no glitches due to USB driver issues (how is the USB-Device on the RPi handled by Roon?)

Thanks for any pointer.


If you have the RPi 2B already why not just try it. the RPi 3 might fare a little better and others like the Allo Sparky might be better suited with some of the RPi USB/LAN conflicts. DietPi is an easy install to try Roon Bridge and a USB output.

I haven’t tried USB on my several RPi 3B’s but I might give it a go with my Emotiva XMC-1 processor with a USB connection just for fun.

Thanks, @Paul_Chatfield, your comment is very helpful, because, in fact, I am completely new to the RPi-cosmos :nerd_face: (as opposed to the computer audio thing).

I don’t own any RPi pcbs but heard of the 2B to form an appropiate platform for HQ audio applications (mostly in conjunction with an audio interface piggy back card). Since I do not want to break up the digital signal chain from source material to the speakers I will only accept components serving this design principle.

So, that’s the background to my quest regarding a “roonified” player endpoint for a USB-DAC-capable digital AV receiver (yes, the Pioneer is fully 32bits digital, including the power amps.

I really have no idea about the RasPi implementation of USB2 and how bad signal quality is electrically but I hope this will not be crucial in an asynchronous environment.

Regarding roon software talking to the USB device I do not have any clue either, but I would love to learn more about it. Do they talk to the USB chip directly or do they make use of a software interface (normal Linux sound architecture or more sophisitcated kernel libraries like AP-Linux etc.)?

Any insights are highly appreciated.


The trouble with the Pi is that it has a common bus for USB and Ethernet. People have reported that this is less of a problem with the Pi3, although the architecture isn’t changed.

I’ve used a Pi2, BBB and CuBox as Roon Bridge devices connecting by USB to an Auralic Vega. I use HQP and upsample everything to DSD 128 (my Vega isn’t upgraded to 256).

I struck some sporadic pops with the Pi2 at DSD 128. I didn’t hear any with 24/192 PCM. I can’t recall hearing any at DSD 64.

If you aren’t intending to go above DSD 64 then I think the Pi2 or Pi3 would be fine. I’d suggest the Pi3 in view of reports from others.

I had no problems with clicks or pops with the CuBox or BeagleBoard Black. I happily used the CuBox until the microRendu arrived.

Diet Pi is such a convenient and lightweight distro (Debian Jessie) however that it would affect my choice of hardware. Not least because it logs to RAM which markedly reduces the risk of SD card corruption on powerdown.

I’d suggest looking at the Allo Sparky, which has just acquired a Diet Pi install and doesn’t have the USB/LAN issues of the Pi.

Roon Bridge uses ALSA so I guess it doesn’t talk to the USB port directly. Diet Pi will install ALSA and Roon Bridge by menu selection.

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2 posts were split to a new topic: Will Roon Bridge run on a Pi 1?

How would you guys feel about a dedicated HAT for Sparky…that takes the USB 2.0 and cleans it to less than 10mV of noise…and lets you use it for transporting to your fav system ?


I think there would be a lot of interest, particularly if it is selectable in dietpi.

I’d certainly purchase one.


I think that Dan would implement it in no time.He is a wizard :slight_smile:

Well… we are already working on it . We have the gerbers ready but its the Chinese Lunar year…so we have to wait at least 3 weeks at least to get our hands on a PCB,
Then we need to test… I am confident about the 10mV of noise but plan on accepting up to 15mV (still better than any other solution)

Filter , filter , filter and then LDOs

1 Like isn’t an Indian venture? (because you’re talking about Chinese holiday season… :smirk:)

Apart from that, yes, count me in. I will give it a try (thanks @andybob) and spread the word in my audio forums over here.
Please, let us know when you finished the filtering HAT for Sparky. I will be the first to get my fingers on…

Our R@D is based in India and some in EU. Management is in EU(apart from our GM) but PCBs are done in China.
Manufacturing is done in Bangalore TI LP38798 - ultra low noise…

LT3042 from Linear…

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uh ok, nice part. So you probably meant 10 µV noise on the USB power line :grin: I would highly appreciate such a device for connecting to external USB-DACs since 10µV seem to be state-of-the-art for DAC HATs as well (see JustBoom – how is the proposed Sparky HAT? Did you already make progress?
Anxiously awaiting …

Yes progress is being made. One problem we had , is that USB power (not usb signals) is 5V. On the board we also have 5v. So we cannot use a LDO to clean the power, what we did is we used a regulated DC/DC convertor with 30mV of noise. Then we filter the output . Still we wont reach 10uV of noise, but rather 1-3mV of noise.

However we the USB lines (data lines) we used LDOs filters etc and there we should have no major problems , noise will be very low. – thank you, johan, would it be feasible to employ a DC/DC converter on the 5V power line? Or do you think this would be overkill and only ruin the price point? :wink:

Apart from this, will your firm be present at EmbeddedWorld2017 over here in Nuremberg/Germany? This would be a home match for me.

We must use galvanic isolated DC/DC convertors…so they go up to 2w = 400ma (5v) thats our target

Next one is 5v/9v …so 9v (to drop to 5v) is 200ma (about)

The problem is not with a 1uv or 1mv of noise. The problem is that your PC is full of hi freq noise in addition to about 75-150mv of ripple

We have no such thing and the 1mV ripple is acceptable even in hi (est) end amplifiers.

Just to be clear, we will have 3 such galvanic isolated convertor. One for the USB ic , one for xtals and last for the USB power. This way we keep the noise separated in the 3 areas (even though we share ground)

It will be the quietest USB output on the market…bar none.

1 Like – Hello Johan, did you make any progress with the USB Sparky HAT or did you abandon the project?

we are in the middle of testing the PCB… it will take about 10 days for news.