[pulseaudio-discuss] Need help resolving audio recording/playback issues

[Sean Greenslade]

On Tue, Feb 08, 2022 at 01:21:24PM -0800, Rich Shepard wrote:
> Something(s) changed here and I don't know enough about linux audio to fix
> the problems.
> 
> Environment: Slackware64-14.2. Audio-Technica AT2005USB, Scarlett Solo Gen
> 3. The latter two are connected by an XLR cable.
> 
> All worked fine until a few days ago. Now pavucontrol Configuration tab sees
> the Scarlett Solo USB connected to the desktop, and the Input Devices tab
> shows three options: Front Microphone (unplugged, although that's where the
> Scarlett Solo is connected), Rear Microphone (plugged in, and the only one
> to show the vu bar responding to noise as well as flickering when there's no
> microphone connected or turned on), and Line In (unplugged).
> 
> Earlier today, using audio-recorder (version 2.2.3) and connecting the
> Audio-Technica AT2005USB with the USB cable I successfully made a test voice
> recording that mplayer sent to the Creative Pebble speakers. I could not
> repeat this later in the morning. While audio-recorder wrote a 327K file,
> aplay, mplayer, and vlc don't produce what I recorded in the .mp3 file.
> 
> Using a new Cable Masters XLR cable I'm still not seeing the Scarlett Solo
> input LED ring flicker when I speak. The AT2005 microphone does work ... at
> least it did earlier today with the USB cable.

On the Scarlett USB interfaces, the green/red LED ring around the input
gain knob is driven directly by the hardware. Pulseaudio has no
influence over this.  So if you're not seeing any signal there, the
issue is in hardware. Make sure:
- The XLR cable is OK and fully seated into the plugs on both ends.
- The switch on the side of the mic is on. It needs to be on to feed
  output to the XLR jack.
- The preamp gain knob on the Scarlett is set high enough. Dynamic mics
  can have pretty weak signals. On mine, I need to pretty much max out
  the preamp to get signals strong enough to light up the green ring.

--Sean