[pulseaudio-discuss] pavucontrol : input device listed, but no signal

Pieter J Voet PieterVoet at nl.ibm.com
Fri May 6 11:33:55 UTC 2022

Hi all,

I'm running Fedora 35 which has pipewire. Next, I have an external USB DAC ( Behringer Firepower FCA610 ).
My speakers are connected to the USB DAC, and it's configured as the default output sink.
This all works fine, audio on my laptop plays thru the USB DAC.
I have three userspace processes running : 'pipewire', 'pipewire-pulse' and 'wireplumber'.

Now, I have a keyboard plugged in the USB DAC analog input, and can hear it's sound on my speakers.
I can  play audio on my laptop, play something on the keyboard simultaneously, and it all plays fine
with audio output on my speakers.

So far, so good. But what I want is to record from the USB DAC analog input.
Unfortunately that's not working. Using Audacity, I can click 'Start Monitoring' , but there's no sound.

To simplify things and rule out Audacity, I see that 'pavucontrol' ( GUI ) lists the UDB DAC both as an Output and an
Input Device. But the 'Input Devices' tab does not show output signal level upon pressing the
keys on the keyboard...
Again, I can hear the keyboard on the USB DAC attached speakers. This means that the input stream
is somehow redirected to the output-sink right ?

I'm a long-time Linux user, but Pipewire/Pulseaudio really confuses me. I don't know what to do..

To make the story even weirder : sometimes after a reboot the USB DAC 'Input Device' actually has
a signal !! And I can then record in Audacity.
But that's 'sometimes'..  My latests attempts by rebooting do not  give me inputsignal level anymore.

This all probably is caused by my lack of knowledge of pipewire/pulseaudio..  but hopefully somebody
can educate me a bit on this.

Thanks in advance for any help !

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