It seems the ADAU1772 does not apply the "initial push button volume" when it is running in self-boot mode. Similar behavior has been observed by others (see other ADAU1772 threads). Is this a ADAU1772 specific problem, or is SigmaStudio simply not including this parameter in the generated EEPROM file?
I found that adding these commands at the end of the EEPROM file fix the problem:
set PB_VOL_CONV_VAL to default (=None)
set PB_VOL_SET at the desired value
set PB_VOL_CONV_VAL to the converter you want to control
This is as described in the ADAU1772 datasheet, page 101:
Address: 0x003F, Reset: 0x00, Name: PB_VOL_SET
This register must be written before Bits PB_VOL_CONV_VAL are set to something other than the default value.
However, in the 'original' EEPROM file the PB_VOL_SET is actually written before the PB_VOL_CONV_VAL are set. Only difference is that they are written in 1 block, so maybe that works out differently.
Unfortunately this is not a fix for the long term. Modifying the EEPROM (including calculating a new checksum) is not very practical. Can this problem please be addressed in the next SigmaStudio release?