BB-BONE-AUDI-02 load without cape

I want to know if it’s possible to load BB-BONE-AUDI-02 via /boot/uEnv.txt and watch digital output on oscilloscope without plug in cape.
I try it (also loading am335x-boneblack-audio.dtb of course), all kernel messages (dmesg) are ok (except i2c register setup, of course, cape isn’t plugged), when I play a wave file with aplay, all seems ok but nothing move on digital audio pin. I use last debian release : Debian 8.5 2016-05-13 4GB SD LXQT
Something strange, removing am335x-boneblack-audio.dtb from uEnv.txt give many kernel error message but soundcard is here (aplay -l) and playing a wave file give signal on oscilloscope. However only dsp_a or dsp_b digital audio format are working and I need I2S, right_J or left_J…
Do I need to do a kernel update?