I suggest you consider updating BIOS to ‘Improve system performance’
ROG Crosshair VIII Hero (WI-FI) | rog.asus.com
The arecord error is correct that there is no device hw:0,0 because HDMI device is shown as card 0 and does not have a capture subdevice
(a USB device would normally be blocked from taking card 0 status by ALSA to allow for HDMI and onboard audio)
The USB Device is now shown as Card 2, but the card number could change if the 3 USB devices are detected in a different order
I suggest you use the card alias name instead of the card number --device="hw:E70,0"
I also suggest add options -c 1 for the mono channel map and -t wav
arecord -d 5 -c 1 -f S16_LE -r 16000 --device="hw:E70,0" -t wav rec.wav
I had hoped that this device would support a better sample rate than 16000Hz but it doesn’t
Sennheiser EPOS GSA 70 at usb-0000:08:00.3-4, full speed : USB Audio
Capture:
Status: Stop
Interface 4
Altset 1
Format: S16_LE
Channels: 1
Endpoint: 3 IN (NONE)
Rates: 16000
Bits: 16
Channel map: MONO
Sennheiser EPOS GSA 70 at usb-0000:08:00.3-4, full speed : USB Audio #1