PinePhone as portable music player with RME Babyface Pro USB audio interface
#1
After over 5 years of owning my Babyface Pro I have finally figured out a practical way to use it outside on battery power thanks to the PinePhone. Despite the Babyface Pro being USB audio class compliant, it does not work with whatever Android puts on top of ALSA. I suspect that has something to do the alternate USB configuration which presents only 2 channels for iOS applications, but I have not actually looked into the problem. Anyway, I now have a solution with my PinePhone:

[Image: q0FSWAF.jpg]

I am using the USB hub that comes with the PinePhone "convergence package" and plugging the Babyface Pro into it. I am plugging the battery into the USB-C Power Delivery port on the hub, which powers both the Babyface Pro and the PinePhone. The PinePhone charges really slowly from the hub, but importantly, it does not drain battery so it can keep playing for a long time.

I have my entire music collection, which is currently 174 GB of FLACs, on a 256 GB microSD card in the PinePhone. I set a fixed mount point for the microSD card in /etc/fstab so music players have a consistent path to scan for music (mounting from Profile or GNOME Files mounts to a different path each time and I'm not sure what determines that path). I have Elisa and Lollypop on my PinePhone. I prefer Elisa, which is what I use on my laptop, but it currently has an annoying bug with one time stuttering a few seconds into the start of tracks, so I am using Lollypop for now. There are several unrelated issues which prevent me from using the PinePhone as my daily driver phone for now, but I have figured out how to make it useful as a portable music player already so it's not just a fun toy.

The speaker is my trusty old Bose Sounddock Portable which is still working well after 10 years. This battery has a 20 V DC output so I can charge the Bose Sounddock Portable directly without needing an inverter and the bulky AC adapter that came with the Bose Sounddock Portable. Its capacity is huge with 266 Wh. I suspect I could use this setup over a whole weekend at a festival without needing to recharge the battery.

This whole setup fits in a normal size backpack and it isn't too heavy.

Notably, there is a faint high pitched ringing sound when everything is connected which goes away if I disconnect the battery from the Bose Sounddock Portable. I do not know what causes that but it is not too bothersome when music is playing. I would appreciate any suggestions to investigate or alleviate that.
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#2
Nice, although the Babyface seems like overkill in this application ;-)

The mixer controls for the Babyface pro only landed in kernel 5.8 so Android won't have that. Whether that's the problem, or it's something else, I don't know. I've not tried my Forte on an android device - that presents as 4 channels, and doesn't yet have mixer support in the kernel.
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#3
(05-12-2021, 07:15 AM)wibble Wrote: Nice, although the Babyface seems like overkill in this application ;-)

The mixer controls for the Babyface pro only landed in kernel 5.8 so Android won't have that. Whether that's the problem, or it's something else, I don't know. I've not tried my Forte on an android device - that presents as 4 channels, and doesn't yet have mixer support in the kernel.
I don't think there is such a thing as overkill for sound quality. The Babyface Pro is backpack portable, but of course not pocket portable. I got one of these tiny USB audio interfaces for use with headphones in my pocket for example on public transit.

The ALSA mixer support is not really relevant. Though it would be amusing to use bbfpromix on my PinePhone to make use of it.

Android has its own awful audio stack on top of ALSA that adds a bunch of latency.

As for the high pitched hum, I figured out it is somehow an artifact of connecting all the devices to the same battery. If I power the PinePhone and Babyface Pro from a different battery pack while charging the speakers from that bigger Renology battery pack, there is no high pitched hum.

I got a ZMI PowerPack 20k Pro which is a battery pack that doubles as a USB hub. However the USB hub functionality is not working for me. It came with a short USB-C to USB-C cable and a long USB-C to USB-C cable for charging. When I switch it to hub mode and plug in with the short cable, either to my laptop (Lenovo Yoga 920) or my PinePhone, dmesg shows:

[170497.081229] hub 4-0:1.0: USB hub found
[170497.081252] hub 4-0:1.0: 2 ports detected
[170498.029555] usb usb1-port6: Cannot enable. Maybe the USB cable is bad?
[170498.029639] usb usb1-port6: attempt power cycle
[170499.293596] usb usb1-port6: Cannot enable. Maybe the USB cable is bad?
[170500.245545] usb usb1-port6: Cannot enable. Maybe the USB cable is bad?
[170500.245622] usb usb1-port6: unable to enumerate USB device

If I use the long USB-C to USB-C cable, dmesg shows:

[171365.862614] hub 4-0:1.0: USB hub found
[171365.862629] hub 4-0:1.0: 2 ports detected
[171366.489474] usb 1-6: new high-speed USB device number 119 using xhci_hcd
[171367.445565] usb usb1-port6: Cannot enable. Maybe the USB cable is bad?
[171368.397564] usb usb1-port6: Cannot enable. Maybe the USB cable is bad?
[171368.397659] usb usb1-port6: attempt power cycle
[171369.034534] usb 1-6: new full-speed USB device number 121 using xhci_hcd
[171369.034717] usb 1-6: Device not responding to setup address.
[171369.238657] usb 1-6: Device not responding to setup address.
[171369.446569] usb 1-6: device not accepting address 121, error -71
[171369.560525] usb 1-6: new full-speed USB device number 122 using xhci_hcd
[171369.560678] usb 1-6: Device not responding to setup address.
[171369.765593] usb 1-6: Device not responding to setup address.
[171369.973489] usb 1-6: device not accepting address 122, error -71
[171369.973606] usb usb1-port6: unable to enumerate USB device

Maybe I've stumbled into USB-C compatibility hell. I'll try getting different USB-C cables. I can already use the ZMI PowerPack 20k Pro by using it to power the Pine USB hub, but it would be nice to not need the Pine USB hub.
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#4
By overkill I mean that unless the Bose performs spectacularly better than similar products it's going to be the limiting factor, even with a cheap but relatively high performing adapter like the Apple one. The amps in such speakers are typically >30dB worse than that dongle. If you're doing some mobile recording then it's another matter entirely. Or doing it just because you can Smile

I can't help on the USB side - I haven't done the necessary hardware mod to my Brave Heart to sort its USB power issues.
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#5
It turned out that the issue I had with the ZMI PowerPack 20k Pro was a defective unit. I exchanged it for another and now it works great with my PinePhone. I can now power my PinePhone and connect my Babyface Pro with one device.
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