Your device seems to have USB controlled volume. By default, Linux sets these to -60 dB or similar for safety reasons.
Login on the console as “root” (no password).
Then run “aplay -l” to list available playback devices. Take note on the card number of RS250.
Then run “alsamixer -c X” where X is number of the RS250 card. Use arrow keys etc to adjust the volume to 0 dBFS. Then hit ESC to exit the mixer control.
Then run “alsactl store” to save the settings for future boots. Now your hardware volume is set to maximum.