USB amp as audio input

thyne · January 2, 2017 at 6:05 PM

Hello,

I am new to LibreELEC (on a Raspberry Pi 3) and I have the following question:

I have a record player which is amplified by a USB amplifier (Texas Instrumemts PCM2094 Audio Codec). This USB amplifier is connected to my Raspberry Pi. A lsusb command shows that the device is connected.
Now, I would like to play my disc records but unfortunately, it does not work. It seems that LibreELEC doesn't recognizes the USB amplifier as an audio input out of the box. And I also don't know how to pipe the audio input to the audio output to hear the music.

I know that the USB amplifier works fine under Linux because I use it with debian. There I just have to type "pactl load-module module-loopback" and everything works fine.

**lrusak** · January 2, 2017 at 6:38 PM Official Post

You'll have to use dtparam=audio=on in config.txt then you might be able to

thyne · January 2, 2017 at 8:45 PM

load-module module-loopback

Thank you for your answer. I put it in the config.txt and rebooted.

But even after "pactl load-module module-loopback" I can hear nothing.

Btw sound works with all other things (Youtube, Radio, etc...)

**lrusak** · January 2, 2017 at 8:53 PM Official Post

You'll have to check the pulse audio routing

Use

Code

pactl info

Then set the correct source and sinks

Or just post the output of that command and

Code

pactl list short

thyne · January 6, 2017 at 4:35 PM

Ok, since I am not able to solve it, here are the outputs:

Code

# pactl info
Server String: /var/run/pulse/native
Library Protocol Version: 30
Server Protocol Version: 30
Is Local: yes
Client Index: 13
Tile Size: 65496
User Name: root
Host Name: seelec
Server Name: pulseaudio
Server Version: 8.0
Default Sample Specification: s16le 2ch 44100Hz
Default Channel Map: front-left,front-right
Default Sink: auto_null
Default Source: auto_null.monitor
Cookie: 25c5:e073


# pactl list short
0    module-native-protocol-unix        
1    module-stream-restore        
2    module-device-restore        
3    module-default-device-restore        
4    module-rescue-streams        
5    module-always-sink        
6    module-null-sink    sink_name=auto_null sink_properties='device.description="Dummy Output"'    
7    module-suspend-on-idle        
8    module-position-event-sounds        
9    module-dbus-protocol        
10    module-bluetooth-policy        
11    module-bluetooth-discover        
12    module-bluez5-discover        
13    module-zeroconf-publish        
14    module-native-protocol-tcp    auth-anonymous=1    
15    module-switch-on-connect        
16    module-loopback        
0    auto_null    module-null-sink.c    s16le 2ch 44100Hz    RUNNING
0    auto_null.monitor    module-null-sink.c    s16le 2ch 44100Hz    RUNNING
0    0    -    module-loopback.c    s16le 2ch 44100Hz
0    0    -    module-loopback.c    s16le 2ch 44100Hz
14    protocol-native.c    pactl

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How can I find the right sink now?

**lrusak** · January 8, 2017 at 5:10 AM Official Post

I don't see the device there at all. You will probably have to load the correct overlay for the device you are using.

Does the device show up in alsa output?

Code

aplay -l

Then you can load the pulse audio udev module.

Code

pactl load-module module-udev-detect

Then the device might show up in pulseaudio

thyne · January 8, 2017 at 1:14 PM

Aha, thank you. The card is indeed listed now (card 2):

Code

# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 0: ALSA [bcm2835 ALSA], device 1: bcm2835 ALSA [bcm2835 IEC958/HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: MobilePre [MobilePre], device 0: USB Audio [USB Audio]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 2: CODEC [USB Audio CODEC], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

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And after "pactl load-module module-udev-detect" it is now also listet in pactl:

Code

# pactl info
Server String: /var/run/pulse/native
Library Protocol Version: 30
Server Protocol Version: 30
Is Local: yes
Client Index: 4
Tile Size: 65496
User Name: root
Host Name: seelec
Server Name: pulseaudio
Server Version: 8.0
Default Sample Specification: s16le 2ch 44100Hz
Default Channel Map: front-left,front-right
Default Sink: alsa_output.0.analog-stereo
Default Source: alsa_input.usb-Burr-Brown_from_TI_USB_Audio_CODEC-00.analog-stereo
Cookie: 8d4e:4b9e

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Unfortunately I can still not hear the record player. Moreover after "pactl load-module module-udev-detect" the sound output is totally distorted and noisy. So I had to unload the module-udev-detect again.

I think there is still something wrong with the input and output settings. Regarding the aplay list, I need card 1 for the sound output and card 2 as the sound input source. Moreover the sound input should be directed to the output.

USB amp as audio input

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