I am planning to use an external Microphone "ReSpeaker 4Mic Hat" from Seeed-Studio on my RPi3 B+ Stretch OS. However, when I run alsamixer, my external Mic is not the default capture device. It seems like bcm2835 is the default soundcard, which means as default I don't have any capture device.
If I launch audacity, I can successfully record sound with the external microphone.
So, where I can set the default setting for Alsa like:
Default Input: "hw1,0",
default output: "hw0,0"