You need to go to test mode and calibrate the vol L and R inputs. You can also edit /contents/prop/ea3-config.xml to change language to English:
 
<soft>
        <model __type="str">KFC</model>
        <dest __type="str">A</dest>  <-- set this line to A for English, J for Japanese -->
        <spec __type="str">F</spec>
        <rev __type="str">A</rev>
        <ext __type="str">2021060802</ext>
    </soft>