[pulseaudio-discuss] No audio output; same setup worked before

[Rich Shepard]

Before getting the USB headsets working (thank you very much!) I used my
AudioTechnica AT2500USB condenser microphone to record the audio portion of
videos. Today I decided to again use it for recording and leave the headsets
for online, virtual meetings. So I set up the AT again.

The AT mic is connected via XLR to a Focusrite Scarlett Solo pre-amp. The
Focusrite is connected via USB to a front panel port on the desktop's case.

I configured pavucontrol so it sees the webcam and the AT mic as inputs; the
audio device is seen as Scarlett Solo USB (rather than AudioTechnica
AT2500USB) and the Input Devices tab shows that same device name with the vu
meter responding to microphone input. A test file created with arecord shows
the audio stream:
$ ffprobe -hide_banner test-mic.wav Input #0, wav, from 'test-mic.wav':
    Duration: 00:00:16.00, bitrate: 64 kb/s
      Stream #0:0: Audio: pcm_u8 ([1][0][0][0] / 0x0001), 8000 Hz, 1 channels, u8, 64 kb/s

The Output Devices tab has only one device: HD Audio Generic Analog Stereo
with the Port Line Out (Plugged In). The external speakers are turned on and
I hear clicks when I adjust the volume on pavucontrol, but no sound when I
play 'test-mic.wav' with aplay.

I've looked at pavucontrol tabs and don't see why I'm not hearing that audio
stream.

What have I missed? Wrong arecord parameters?

Rich