Small appliances have microcomputer that requires 5V power supply. Why it can use only 1.5V battery? The 1.5V to 5V boost converter circuit inside them.
Your amplifier may sound better than before. Just change the appropriate power supply circuit. Multiple levels of output voltage. For example 15V Dual regulator for pre amplifier. And 38V Dual for main amplifier etc.
This is dual 15v power supply schematic, using LM7815,LM7915,and power transistor and zener diode for voltage stable voltage 15 volts positive and negative. [...]
This is a 0-60V, Dual Variable power supply circuit using LM317 and LM337 at 1.5A current so can builds to easy with PCB layout, adjustable voltage VR1,VR2 [...]
If you need a dual power supply. But you only have a single supply source. So should build this power supply splitter circuit.