Adding 2 cooling fans to an amplifier circuit board

You need to investigate Voltage Regulators (LM78xx-type, but suitable for 40V or more input) and/or Buck Converters. And also use a bridge rectifier, since you now have a magic ground that's connected to nothing. The electrons can't read your mind about where you want them to go, so they won't go.

Series resistors are the worst possible method to make a stable and reliable voltage for anything that hasn't got the most stable current consumption imaginable. Audio circuits do not qualify for stable power needs.