The music and most of the callouts in my Whirlwind sound just fine, but a few of the callouts are very low and difficult to hear. I took a look at the pinwiki for help in troubleshooting this issue and found a section that talks about this can be an issue if a system 11a CPU board is used in a system 11b game. I confirmed that someone had swapped a system 11a board into this game at some point. The pinwiki also shows the differences in values for resistors and capacitors in the sound section of the CPU board.

Can I simply update the resistors and capacitors on my system 11a CPU board to fix this sound issue? I'm assuming yes, but would like to get confirmation.

https://www.pinwiki.com/wiki/index.php?title=Williams_System_9_-_11#Voice_callouts_are_much_softer_than_music.2Fsound

Thanks for the confirmation. I made the changes this morning and all my callouts are at the same volume level now.