PS Audio moving coil phono preamp modification to vastly improve the signal to noise ratio.
Now – Zero hum from power supply.
Here’s the solution.
Absolutely dead quiet. Double regulation.
First stage down to +/- 17.3
Second stage down to +/- 15
Less than 2mV noise on DC rails where before was close to 2 V of ripple and noise on the pre-regulated side plus the filter caps were too far from the rectifier diodes putting noise on the main pcb.