Isolated power supply for effect pedals

I got some nasty noise problems when I tried to use all effect pedals with just one 9 V power supply. Problem was solved by using separate power supplies for digital and analog effects. However, a power supply with two isolated outputs would be a more elegant solution. Luckily I had suitable parts to build one.
schematic diagram
Here is the schematic diagram. The mains transformer has two separate 12 V windings feeding identical regulator circuits. I used LM317 because I had several of them. I would have been happy with fixed 9V output voltage, but I didn't have resistors with just right values - so I used trimmer pots instead. Voltage can be adjusted from 4,4 to 13,9 volts.

inside view

©Jukka Korppi 2020
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