snd-usb-audio-audient-evo8

Modified version of snd-usb-audio allowing alsamixer to control the real-time monitoring mix.

Building and loading the module

Clone the repository and run the following commands to build the modified kernel module:

make

Now manually unload the default snd-usb-audio module and replace it with the modified one:

sudo modprobe -r snd-usb-audio
sudo modprobe -r snd-usbmidi-lib
sudo insmod usb/snd-usbmidi-lib.ko
sudo insmod usb/snd-usb-audio.ko ignore_ctl_error=1

Note that this only works until you reboot.

When the kernel is updated on your system, you may need to build this kernel module again:

make clean
make

Real-time monitoring control

In a terminal, run alsamixer and click F6 to find the EVO8 controls.

For each microphone input there is a control for each output. The routing is shown below.

The following commands sets the microphone gain and monitoring to 0 %:

amixer -q -c EVO8 sset 'Mic' 0%
amixer -q -c EVO8 sset 'Mic 1 mix' 0%
amixer -q -c EVO8 sset 'Mic 2 mix' 0%
amixer -q -c EVO8 sset 'Mic 3 mix' 0%
amixer -q -c EVO8 sset 'Mic 4 mix' 0%

DAW output routing control

Like above, there is also a routing from each DAW output to each physical output. The routing below shows how to separate DAW output 1-4 into the physical output 1-4.

The following commands set up the DAW routing as shown above:

amixer -q -c EVO8 sset 'DAW 1 mix' 100%,0%,0%,0%
amixer -q -c EVO8 sset 'DAW 2 mix' 0%,100%,0%,0%
amixer -q -c EVO8 sset 'DAW 3 mix' 0%,0%,100%,0%
amixer -q -c EVO8 sset 'DAW 4 mix' 0%,0%,0%,100%

NOTE: I have noticed that somethimes the output routing does not work right away on output 3L and 4R. This seems to be fixable like this:

1. Go to alsamixer
2. Find DAW 3 mix
3. Turn the left channel volume down one step by typing `z´
4. Turn the left channel volume up one step by typing `q´
5. Find DAW 4 mix
6. Turn the right cnannel volume down one step by typing `c´
7. Turn the right channel volume up one step by typing `e´

I am sure this can be done with the amixer commands as well but I have not tried yet.

Known limitations

As shown above, the kernel module must me loaded with the ignore_ctl_error=1 flag - otherwise alsamixer will crash. The dmesg output shows the following message:

cannot get ctl value: req = 0x81, wValue = 0x100, wIndex = 0x3200, type = 0

The modifications have only been tested on the EVO8 but it may be ported to the EVO4 with minor modifications.

References

I have created another tool for directly adjusting the mixer control values: evoctl. This, however, detaches the kernel driver, and can therefore not be used while JACK is running. Have a look there to get more details about the internals of the EVO 8.