This is in addition to our previous LM317 LM337 power supply.. minor change in removing one of the resistors and substituting it for a 5k trimpot.
You will need a centre tapped transformer to get the negative voltage to regulate eg 15v-0v-15v etc
Etch at Home Files available HERE
C1 & C2 1000uf 50v
R1 & R3 5k 25 turn trimpot
All Diodes 1n4004
All other capacitors rated at 25v – use larger voltage if you are going to regulate 18-24v or higher.