Volumio USB Audio on RPi2

Audio Gear DACs
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As there doesn’t appear to be much information available on this yet, I thought I’d post my experiences using Volumio and USB Audio on the new Raspberry Pi v2. TL;DR: it’s MUCH better (for me).

First, some background: I have a Raspberry Pi B and B+, and also a HummingBoard. I have tried and compared all of these using Volumio. I’m using an Arcam IRDAC (async USB 2.0) connected via analog cables to a powered amp -> Tetra speakers, also via HeadRoom Little More power amp -> HD800’s. My test track is “Lucia” from the HDTracks 96/24 sample pack (although same outcome applies to other tracks I’ve tried).

On both my B and B+, I hear soft pops in the audio. These occur randomly from once per second to every few seconds. If you’re just passing by, you might not notice them, but if you’re really listening they are quite easy to discern and significantly taint the experience. I’ve tried using previous releases of kernel/firmware, the latest one that ships with Volumio 1.55, and the very latest as of Feb 26, 2015:

cat /proot@(none):~# cat /proc/version
Linux version 3.18.5+ (dc4@dc4-XPS13-9333) (gcc version 4.8.3 20140303 (prerelease) (crosstool-NG linaro-1.13.1+bzr2650 - Linaro GCC 2014.03) ) #748 PREEMPT Wed Feb 4 21:24:41 GMT 2015

root@(none):~# /opt/vc/bin/vcgencmd version
Feb 4 2015 21:00:57
Copyright © 2012 Broadcom
version 115f63aa0915cdb5b6dff23822eb16699b72ae8b (clean) (release)

After running rpi-upgrade:

root@(none):~# cat /proc/version
Linux version 3.18.7+ (dc4@dc4-XPS13-9333) (gcc version 4.8.3 20140303 (prerelease) (crosstool-NG linaro-1.13.1+bzr2650 - Linaro GCC 2014.03) ) #759 PREEMPT Thu Feb 26 15:50:00 GMT 2015

root@(none):~# /opt/vc/bin/vcgencmd version
Feb 26 2015 15:56:04
Copyright © 2012 Broadcom
version e987975e117c6c63876e726aa1282b4705ab2849 (clean) (release)

When I disconnect all USB devices expect for my DAC and use RamPlay, I still experience the problem. When I run Volumio 1.5 on my HummingBoard with the same setup, I hear no such pops. This problem appears to be specific to Raspberry Pi (B/B+).

I’m pleased to now report that the pops go away completely running Volumio 1.55 on my shiny new v2 Pi. I hear no audible issues whatsoever; the sound is smooth and awesome, just like on my HummingBoard.

This particular issue may be specific to my DAC, so YMMV. But it seems like a good sign for USB audio on Rpi v2.

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Hopefully, the addtitional CPU power (and memory) of the new RPi 2 B gives it some more punch to handle the USB interrupts better. Maybe also the upgrade from ARM v6 to ARM v7 can bring some extra’s as well.

I personally think that the snd_usb_audio module is one of the most important factors in this use case. If we can use more recent (and ARM v7 optimized) versions with Volumio that might improve also.

Nevertheless, I agree that it can help to get the RPi 2 B instead of the RPi B(+) when you want to use USB audio. Only stability might not be at the same level as with the older Pi’s yet.

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I fixed my popping problem by soldering a ground wire from a usb shroud on the PI to the ground wire of the power supply.

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Picture? :slight_smile:

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IMG_2010[1].JPG