sorry that the first message was sent before I could finish explaining. my fault, please excuse.
I am using an 8 channel USB sound card as an audio source and the first test I do is to ensure that the audio signals can be seen in the attached QT scope block screen shot. This works perfectly when the PC is first started, however when I stop the flow graph and then start it again I get an alsa error message.
When the flow graph is working correctly I get the following message:
<<< Welcome to GNU Radio Companion 3.7.5git-0-g2bb2b314 >>>
Preferences file: /home/drdc/.grc
Loading: "/home/drdc/Documents/8 ip switch test.grc"
Showing: "/home/drdc/Documents/8 ip switch test.grc"
Using Volk machine: avx_32_mmx
After the flowgraph is restarted I get the error message that can be seen in the attached screen shot. running sudo alsa force-reload does not fix the problem. Only a reboot will fix it.
To get the USB sound card to work at all I have done the following:
1 removed pulseaudio
2 blacklisted the internal sound card
3 running aplay -l lists only the USB sound card (exactly what I need)
The audio source block device ID must be left blank to work
If I specify hw:0,0 or plughw:0,0 I get errors telling me that I am not using enough ports or am using too many ports. I think that it is looking at the SPDIF and MIDI ports on the USB sound card that I do not use.
As always any advise is appreciated.