AirPlay with Roon Sound Distortion Bug

BelsizeEye · January 23, 2021, 3:24pm

Core Machine (Operating system/System info/Roon build number)

Mac Mini MacOS version server OSX 10.10.5 / 2.5Gh Intel i5 4GB 1600GHz DDR3
Roon Core 1.7 build 710 stable

Network Details (Including networking gear model/manufacturer and if on WiFi/Ethernet)

Gigabit Ethernet Cat 5e all going through high grade gigabit switches

RAAT 100% reliable up to DSD256 no drop outs.

Audio Devices (Specify what device you’re using and its connection type - USB/HDMI/etc.)

Pioneer N-30 Network Audio Player used as bridge with coaxial digital out to Sennheiser HDVD800

When selecting Pioneer N-30 as an AirPlay device to act as an destination for streamed TIDAL, QOBUZ or local server based music. On occasion the resultant stream on Pioneer N-30 can suffer digital artifact distortion but only when tracks being played originate at 44.1 / 24 if higher resolution such as 88.2, 96 or 192 / 24 then non such distortions exists.

If however same affected tracks are played from iPad on iOS over AirPlay to N-30 from either QOBUZ OR TIDAL then distortion on affected track is NOT present.

Therefore, this particular issue is only Roon Core specific.

For reference Roon Core is well specified Mac mini dedicated to task built as a server connected only via gigabit Ethernet and cpu is only around 20% when Roon is playing requested track.

My belief is that since Roon does not use official Apple Mfi AirPlay stack but rather a third party emulation that there is slight compatibility issue with AirPlay version 1 which is used by Pioneer N-30 NAP and similar older gen AirPlay devices.

The problem is in part due to Airplay 1 only supporting 44.1 / 16 and the required 44.1 / 24 to 44.1 /16 dither algorithm used by the AirPlay sender on core is creating the distortion that effects certain frequencies creating a slight distortion effect much like slight over tracking errors that can affect bad recordings.

On AirPlay products such as Apple HomePod which uses AirPlay version 2 the problem does not occur at all when streaming from Roon to HomePod or at least can not be heard.

Hopefully, a Roon engineer will see this posting and make some determinations on a possible resolution.

noris · February 10, 2021, 8:02pm

Hi @BelsizeEye,

Is this behavior still occurring on the latest Roon release?
Does the distortion also happen if using Analog RCA output and bypass the Sennheiser?

BelsizeEye · February 11, 2021, 9:43pm

Yes same distortion issue on version 1.8 no change. Check it your self with Nemesis track last closing 20 seconds

You may like to consider making me a beta tester as I am a software developer and have extensive experience at software testing.

In relation to your other question on analogue feed out from Digital Audio Player which has AirPlay support the distortion sound effect when it occurs is exactly the same whether it emerges from the the digital output or whether it is from the analogue output.

Clearly the artifact distortion is in the AirPlay processing from Roon and only as described in my original post. Problem does not occur with high resolution files of 96/24 and above where the 64 bit conversion to 44.1/16 creates the dither type of distortion on certain frequencies.

BelsizeEye · February 18, 2021, 11:00am

Noted still no reply.

Looks like you have no idea of solution

noris · February 19, 2021, 8:17pm

Hi @BelsizeEye ,

Apologies for the delay in getting back to you here. I did speak to the team regarding your case and they mentioned that this track is mastered very loudly towards the end. Can you please check to see if using the DSP Engine and adding a bit of Headroom Management and enabling the clipping indicator helps? I suggest you start with -3dB.

BelsizeEye · February 19, 2021, 9:04pm

Thank you for getting back. Yes I have tried this, even increasing headroom to -10 which marginally helped but made replay naturally quieter, which required increase to master volume where again the distortion effect could be heard.

It may help to say that when playing same track at same section using Qobuz app set to output to same AirPlay Network Media Renderer. No distortion was present with this track or any other recordings.

The distortion is in most recordings sadly from Roon on AirPlay but on RAAT to Roon endpoint naturally but perfect no distortion.

system · October 14, 2022, 4:51pm

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