More about 9 volts DC power supply or 9V voltage regulator
First choice of Fixed Regulator using family IC-78xx. It is easy to use, cheap, popular for a long time.
Many Fixed Regulator Circuits 5V,6V,9V,10V,12V 1A using IC-78xx series
Modify power supply source in old circuit PCB. I then build to is 9v regulated power supply circuit , that can give current 1 to 2Amp. Look 3 circuit below
It is an old circuit. But it may be useful for you. Learn it now!
This is Diy digital voltmeter panel meter 0-50V is 0-50V scale. Display with LED 7 segment. In cost 3$ dollar only, builds simple regulator dc power supply
I collect these transformerless power supply circuit, use a capacitor instead, it smaller and lighter than transformer. There are circuits as follows.